Acta Polytechnica https://doi.org/10.14311/AP.2021.61.0570 Acta Polytechnica 61(4):570–578, 2021 © 2021 The Author(s). Licensed under a CC-BY 4.0 licence Published by the Czech Technical University in Prague UTILIZATION OF AGRICULTURAL WASTE ADSORBENT FOR THE REMOVAL OF LEAD IONS FROM AQUEOUS SOLUTIONS Adeyinka Sikiru Yusuffa, ∗, Lekan Taofeek Popoolaa, Victor Anochieb a Afe Babalola University, College of Engineering, Department of Chemical & Petroleum Engineering, Afe Babalola Way, Ado-Ekiti, Ekiti State, Nigeria b Baze University, Faculty of Engineering, Department of Petroleum and Gas Engineering, Abuja, Nigeria ∗ corresponding author: yusuffas@abuad.edu.ng Abstract. This work investigated the potentiality of using chemically modified onion skin waste (CMOSW) as an adsorbent for the removal of lead ions (Pb2+) from an aqueous solution. The material properties were characterized using techniques, such as Brunauer-Emmett-Teller surface area analysis, scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy. The effects of adsorbent dosage, contact time, pH and initial Pb2+ concentration on the removal efficiency were investigated by experimental tests. The experimental data were analysed by the Langmuir and Freundlich isotherms, while kinetic data obtained at different concentrations were analysed using a pseudo-first-order and pseudo-second-order models. A distinct adsorption of Pb2+ was revealed by the SEM results. From the FTIR analysis, the experimental result was corresponded to the peak changes of the spectra obtained before and after the adsorption of Pb2+. The maximum removal efficiency of Pb2+ by the CMOSW was 97.3 ± 0.01 % at an optimum CMOSW dosage of 1.4 g/L, contact time of 120 min and solution pH of 6.0. Experimental data obtained fitted well with the Freundlich isotherm model. The kinetics of the Pb2+ adsorption by CMOSW appeared to be better described by the pseudo-second-order model, suggesting the chemisorption mechanism dominance. Keywords: Lead ions, onion skin, adsorption, isotherm, kinetics. 1. Introduction The increased level of environmental contamination as a result of industrial development by compounds of organic and inorganic sources has become one of the major environmental concerns of many industries [1]. Most water contaminants, such as hydrocarbon, phe- nolic, dyes, solvent and heavy metals, are soluble chemical substances [2]. These compounds end up in water bodies, causing water and soil pollutions, and thereby constitute threats to plants, animals and hu- man health [1]. However, the presence of toxic heavy metals in industrial effluents gives a cause for environ- mental concern [3]. Heavy metals are generally toxic, highly soluble in water and can easily find their way into the soil and flowing streams, thereby causing dam- age to the environment and human health. Lead is known as multifunctional metal, which is a needed ele- ment to manufacture pipe, paints, bullets and also one of the essential metals used in the pewter industry [4]. However, a long term exposure to lead ions (Pb2+) can cause mental illness, infertility in women and dam- age to vital human internal organs [5]. Thus, there is a need to adopt a technology suitable for getting rid of toxic heavy metals and other dissolved contaminants from effluents prior to their discharge into flowing streams. The Nigerian Ministry of Environment rec- ommends 0.01 mg/L as the maximum permitted level of Pb2+ in an industrial effluent before its release into surface waters [6] while it has a maximum allowable limit (sets by World Health Organization, WHO) of 0.003 mg/L in drinking water [7]. However, many wastewater treatment methods have been employed in removing toxic heavy metals from the aqueous environment. These methods include electrocoagulation, reverse osmosis, chemical precipi- tation, electrochemical reduction, ion-exchange mem- brane and adsorption [8, 9]. Among these treatment techniques, adsorption seems to be cost-effective, easy and simple to operate [10]. Another advantage of adsorption over other techniques is its capability to treat wastewater pollutants at low concentrations [11]. Some of the porous materials that have been synthe- sized as adsorbents for the removal of toxic heavy metals include activated carbon, molecular sieve and zeolite. These materials are often used to remove toxic metal ions from contaminated water due to their bet- ter surface properties and adsorption capacities [12]. However, they are expensive and challenging to be regenerated and reused. These drawbacks necessitate the need to explore cheap, reusable and biodegradable adsorbents for the removal of toxic metal ions from aqueous solutions. Adsorbents could be obtained from different sources, such as naturally occurring, agricul- tural biomass and waste materials [13–15]. In order to minimize the wastewater treatment costs and avoid the accumulation of solid waste in the environment, agricultural wastes have been suggested and studied, such as pineapple stem [16], pineapple fruit peel [17], waste tea [18], walnut shell [19], peanut shell [20] and 570 https://doi.org/10.14311/AP.2021.61.0570 https://creativecommons.org/licenses/by/4.0/ https://www.cvut.cz/en vol. 61 no. 4/2021 Utilization of agricultural waste adsorbent for . . . seed pod [21]. Moreover, onion skins are abundantly available and can be a good source of electrostatically active metal oxides [22]. According to the literature research, a modification of onion skin waste by acid activation is currently be- ing used, and a series of technical challenges are being experienced [23–25]. The promising use of onion skin requires a modification without severely damaging its structure. However, metal oxides, such as an alu- minium oxide (Al2O3) and silicon oxide (SiO2), could be used to modify the structure of the adsorbent due to their better textural properties, mechanical and thermal stabilities [26, 27]. The application of Al2O3 modified onion skin waste for the removal of heavy metals from aqueous solution is still not well explored. The aim of the current work was to investigate the potentiality of utilizing onion skin waste as an adsorbent for the removal of lead ions from an aqueous solution. The operational parameters’ effect on the uptake efficiency, including initial concentration, pH, adsorbent dosage and contact time, was investigated. The equilibrium adsorption isotherm and kinetics were also studied. 2. Methodology 2.1. Materials Onion skin waste was collected from Oja-Oba, Ado- Ekiti, Nigeria. Lead II nitrate (Pb (NO3)2), hydrochlo- ric acid (HCl), sodium hydroxide (NaOH) and alu- minium nitrate (Al(NO3)3) were all bought from Ni- zochem Chemical Enterprise, Akure, Nigeria. Pb (NO3)2 was used as the adsorbate. 1000 mg/L of lead salt solution was prepared by dissolving 1.60 g of (Pb (NO3)2) in 1 L of deionized water and solutions with different concentrations were prepared from the standard solution. 2.2. Preparation and characterization of adsorbent The collected onion skin waste (OSW) were thoroughly washed with clean water to get rid of dirt particles and dried at 110 °C for 24 h. Then, the dried OSW was grinded and finally sieved through a 220 µm mesh size to remove larger parts. In order to prepare a chemi- cally modified onion skin waste (CMOSW) adsorbent, the OSW powder was mixed with Al(NO3)3 in a ratio of 1:2, and 150 mL of distilled water was added to the resulting solid mixture. Thereafter, the solution was agitated on a hot plate at 75 °C for 12 h and NH4OH solution was subsequently added dropwise to obtain a basic solution and achieve a complete precipitation. The precipitate was washed severally with deionized water, then dried at 110 °C, and finally calcined at 600 °C for 2.5 h. A morphological analysis was conducted on the CMOSW sample to evaluate its surface morphology before and after the adsorption of lead ions using a scanning electron microscope (SEM, JEOL-JSM 7650F). The Fourier transform infrared (FTIR) spec- trometer (FTIR-1S Shimadzu, Japan) was used to determine the functional groups present on the pre- pared adsorbent. The spectra were recorded within the range of 4000-400 cm−1. The textural characteris- tics of the CMOSW samples including specific surface area, total pore volume and pore size distribution were obtained through N2 adsorption-desorption data at -196 °C using a BELSORP Max surface area and porosity analyser (BEL, Japan). The studied samples were degassed before the analysis at 250 °C for 3 h to remove the adsorbed gases that filled up their pores, and their specific surface areas were computed using the Brunauer-Emmett-Teller (BET) model. The total pore volume and pore size were determined by the Barrett-Joyner-Halenda (BJH) method and studied near the saturation pressure of N2 (P/P0 = 0.99). 2.3. Adsorption experiments A required volume of lead salt contaminated water (50 mL) and the needed amount of the prepared ad- sorbent were charged into 250 mL conical flasks. The mixtures were agitated in a temperature-controlled water bath shaker at 28 ± 2 °C and 200 rpm until an equilibrium was attained. The adsorption of Pb2+ ions onto CMOSW was carried out under these operating conditions: initial Pb2+ concentration (10-200 mg/L), solution pH (2-10), CMOSW dosage (0.2-1.6 g/L) and contact time (30-180 min). After the batch adsorption experiment was com- pleted, the adsorbent was removed from the suspen- sion using a centrifuge and the residual Pb2+ con- centration was measured by an atomic absorption spectrophotometer (Model VGP 210, US). The quan- tity of Pb2+ removed at the equilibrium, qe (mg/g) and the removal percentage, Y (%) were determined as follows: qe = (Co − Ce) × V m (1) Y = (Co − Ce) Co × 100 % (2) 2.4. Adsorption isotherm Two-parameter isotherm model (Langmuir and Fre- undlich) was employed in evaluating the experimental data for the Pb2+ adsorption by CMOSW. The non- linear isotherm models are as given by Eqs. 3 and 4. qe = qmaxbCe (1 + bCe) (Langmuir model) (3) qe = kF C 1/ne (Freundlich model) (4) 571 A. S. Yusuff, L. T. Popoola, V. Anochie Acta Polytechnica (a). (b). Figure 1. SEM micrographs of CMOSW sample (a) prior to and (b) after Pb2+ ions adsorption. Separation factor (RL), a dimensionless parameter, was applied in determining the nature of Pb2+ adsorp- tion onto the CMOSW adsorbent. The dimensionless parameter signifies whether the adsorption process is favourable (0 < RL < 1), non-favourable (RL > 1), linear (RL = 1) or irreversible (RL = 0). RL = 1 (1 + bCO ) (5) 2.5. Adsorption kinetics Adsorption kinetics describes the rate at which the amount of adsorbate removed varies with time. The kinetic data for the adsorption of the Pb2+ onto chem- ically modified onion skin were analysed using pseudo- first-order and pseudo-second-order kinetic equations. log (qe − qt) = log qe − ( k1 2.303 ) t (6) (Pseudo-first-order) t qt = 1 k2q2e + ( 1 qe ) t (7) (Pseudo-second-order) 3. Results and discussion 3.1. Characterization of CMOSW adsorbent The morphological structure of the prepared CMOSW before and after the Pb2+ adsorption was determined using the SEM analysis, and the micrographs are shown in Figure 1. Figrue 1a revealed that the pre- pared adsorbent had an almost regular surface con- taining a long but tiny cavity and pores of different sizes, suggesting a reasonable possibility of a rapid adsorption of the Pb2+ ions. However, upon adsorp- tion of the cation, that large cavity, earlier observed on the fresh CMOSW sample, was filled as a result of the Pb2+ adsorption. The FTIR spectrum of the CMOSW adsorbent be- fore the adsorption of Pb2+ is displayed in Figure 2 (a) with several bands at 3496.21 cm−1 (O-H stretch- ing vibration), 2968.87 cm−1, 2980.24 cm−1 (C-H asymmetric and symmetric stretching), 1654.06 cm−1 (C=O deformation), 1380.71 cm−1 (CH3 deformation), 1086.23 cm−1 (-C-NH3 primary aliphatic amine), 652.45 cm−1 (C-O-H twist broad) and 458.34 cm−1 (C-N-C bending modes). The detection of all these functional groups was an indication that the CMOSW adsorbent was complex. However, upon adsorption of the metal ions (Figure 2 (b)), some peaks shifted, and new bands at 3452.26 cm−1 (O-H stretching vibration), 1698.17 cm−1 (C=O deformation), and 400.57 cm−1 (-C-N-C bending modes) were also formed. Figure 2. FTIR spectra of CMOSW sample (a) prior to and (b) after Pb2+ ions adsorption. 572 vol. 61 no. 4/2021 Utilization of agricultural waste adsorbent for . . . Sample Specific area (m2/g) Pore volume (cm3/g) Pore diameter (Å) Fresh CMOSW 26.5 0.17 317.9 CMOSW loaded with Pb2+ 2.8 0.01 201.7 Table 1. Textural characteristics of CMOSW before and after adsorption of lead ions. Table 1 presents the textural properties of the pre- pared CMOSW adsorbent before and after the loading of lead ions. The results showed that the fresh ad- sorbent possessed a large surface area and pore size distribution, and this was an indication that the stud- ied sample had several sorption sites on its surface. The BET surface area of the prepared composite ad- sorbent was 26.5 m2/g, as seen in Table 1, which was above the surface areas of the acid-modified onion skin (10.62 m2/g) [23] and garlic waste (5.62 m2/g) [28]. However, there was a significant reduction in textu- ral properties (surface area, total pore volume and average pore diameter) of the CMOSW sample after the adsorption of Pb2+. These observations were at- tributed to the agglomeration or overlapping of the sorption sites available for the adsorbates, as corrobo- rated by the SEM result. 3.2. Influence of adsorption process parameters 3.2.1. Influence of initial lead ions concentration The influence of the initial Pb2+ concentration (10- 200 mg/L) on the adsorption process was investigated by treating the lead salt contaminated solution at room temperature and pH of 6.0 for 120 min using 1.0 g/L of the CMOSW sample. Figure 3 revealed that the removal percentage decreased, and the equi- librium adsorption capacity increased as the lead ions concentration increased. This observation was due to the same number of adsorption sites, which were available for the increasing adsorbate concentration. It could be deduced that at a higher concentration of Pb2+ ions, the sorption sites on the CMOSW surface for the electrostatic attraction were occupied by more contaminants, thus leading to an increase in equilib- rium uptake capacity of the CMOSW adsorbent and a decrease in the removal percentage of the adsor- bate [29]. Similar observations were also reported for an adsorptive removal of heavy metals by Moringa stenopetala bark powder [30], prawn shells [31] and paper mill sludge activated carbon [10]. 3.2.2. Influence of contact time Figure 4 shows the effect of the contact time on the re- moval percentage and equilibrium adsorption capacity at a fixed Pb2+ concentration of 50 mg/L, pH of 6 and a CMOSW dosage of 1.0 g/L. The figure revealed that both the removal percentage and equilibrium adsorp- tion capacity speedily increased with an increase in the contact time and then decreased until an equilibrium was attained. Generally, a prolonged contact time Figure 3. Influence of initial concentration on Pb2+ adsorption onto CMOSW. favours the adsorption process by enhancing the up- take of adsorbate and also increasing the equilibrium sorption capacity of the adsorbent [16]. As seen in the figure, after the contact time reached 120 min, both the removal percentage and the sorption capacity plots became nearly flat, which indicated that the adsorp- tion equilibrium had been reached. This observation agrees with the work reported for a Pb2+ removal from aqueous solutions by inactive biomass [5], Moringa stenopetala bark [30] and dead anaerobic biomass [32]. Figure 4. Influence of contact time on Pb2+ adsorp- tion onto CMOSW. 3.2.3. Influence of adsorbent dosage To investigate the influence of the CMOSW dosage on the adsorption of lead ions, we used different quantities 573 A. S. Yusuff, L. T. Popoola, V. Anochie Acta Polytechnica of the CMOSW sample (0.2-1.6 g/L) to treat a lead ion- containing solution at a fixed adsorbate concentration of 50 mg/L, solution pH of 6.0 and a contact time of 120 min. The results showed that the removal percentage of Pb2+ increased as the CMOSW loading also increased, while the adsorption capacity exhibited a reverse trend. When the adsorbent dosage rose from 0.2 to 1.6 g/L, the removal percentage increased from 47.98 to 98.24 % because of more active sites for Pb2+ ions and the equilibrium sorption capacity decreased from 5.99 to 1.54 mg/g. A similar observation was also reported for a Pb2+ ion removal by soil [33]. Figure 5. Influence of adsorbent dosage on Pb2+ adsorption onto CMOSW. 3.2.4. Influence of aqueous solution pH The influence of pH on the adsorption of lead ions onto a chemically modified onion skin waste was stud- ied at a fixed initial Pb2+ concentration of 50 mg/L, a contact time of 120 min and an adsorbent dosage of 1.4 g/L. Figure 6 shows a combined plot of removal percentages and adsorption capacity of Pb2+ versus the pH of the simulated solutions. The figure showed that the removal percentages of the cation increased as the pH increased from 2 to 6 and then decreased after the aqueous solution pH exceeded the optimum value. This result indicated that a substantial amount of lead ions could be adsorbed by the CMOSW adsorbent under acidic conditions. In contrast, the adsorption of Pb2+ significantly decreases under basic conditions. 3.3. Adsorption isotherms The non-linear plot of the quantity of Pb2+ adsorbed at the equilibrium against the equilibrium concentra- tion for the Langmuir model, Freundlich model and experimental data are displayed in Figure 7. The estimated isotherm parameters, which were obtained from the plot, are presented in Table 2. The best among the models was selected based on the value of the coefficient of determination (R2). Therefore, the R2 value (0.9881) suggested that the experimen- tal data better fitted the Freundlich isotherm model. Figure 6. Influence of pH on Pb2+ adsorption onto CMOSW. A similar observation was also reported for a Pb2+ adsorption by polypyrole-based activated carbon [34] and hazelnut husks based activated carbon [35]. The values of the separation factor and Freundlich exponent for the lead ions, as can be seen in Table 2, suggested favourability and capacity of the Pb2+ ions – CMOSW system [36]. By comparing the adequacy of the two isotherm models, it can be concluded that the Freundlich isotherm was suitable to describe the Pb2+ adsorption onto the chemically modified onion skin waste. Figure 7. Application of two-parameter isotherm to Pb2+ adsorption onto CMOSW. The monolayer adsorption capacity of CMOSW was compared with other reported adsorbents for the ad- sorption of Pb2+ from an aqueous solution at different optimum operational parameters, as shown in Table 3. The Table showed that the CMOSW adsorbent had a strong affinity for the Pb2+ removal from an aque- ous solution by exhibiting a high maximum uptake capacity of 7.16 mg/g. This value was obtained under the optimum process condition of 50 mg/L initial concentration (Co), 120 min contact time (t), 1.40 g/L 574 vol. 61 no. 4/2021 Utilization of agricultural waste adsorbent for . . . Isotherm Value Unit Langmuir qmax 7.16 mg·g−1 b 0.09 L·mg−1 R2 0.9847 – RL 0.05 – Average relative error 0.128 – Freundlich kF 1.19 Mg·g−1(L·mg−1)1/n n 2.50 – R2 0.9881 – Average relative error 0.050 – Table 2. Values of two-parameter isotherm constants. Adsorbent source qm Experimental condition Reference (mg/g) Co (mg/L) t (min) d (g/L) pH T (°C) Apricot stone 21.38 50 – 1.0 6.0 20 [37] Hazelnut husk 13.05 200 – 12.0 5.7 18 [35] Sand 21.78 50 30 2.0 2.0 65 [38] Groundnut shell 3.428 75 90 8.0 6.0 – [39] Soya bean 0.55 – 60 3.0 4.0 ± 0.26 37 [40] Moringa stenopetala bark 35.71 10 120 1.5 5.0 40 [30] CMOSW 7.16 50 120 1.4 6.0 28 ± 2 Present study Table 3. Comparison of the adsorption capacities of different adsorbents for Pb2+ removal. adsorbent dosage (d), pH of 6.0, and 28 ± 2 °C tem- perature (T). These findings indicated that CMOSW was an efficient adsorbent for lead ions removal from water/wastewater, mostly when compared with those adsorbents derived from groundnut shell [39] and soya bean [40]. 3.4. Adsorption kinetics The plot of log(qe − qt) against t (pseudo-first-order) and t/qt against t (pseudo-second-order), from which the rate constants (k1 and k2) and predicted quan- tity of Pb2+ adsorbed at the equilibrium (qe) were determined, are shown in Figure 8. The estimated kinetic parameters and R2 values are given in Table 4. The results revealed that the predicted qe did not correlate with the observed qe in the case of pseudo- first-order kinetic. Besides, its R2 value (0.9773) was lower than that of the pseudo-second-order kinetic model. Therefore, the pseudo-second-order kinetic model was applied to evaluate the obtained adsorption data. The result obtained showed that the predicted qe was found to be in agreement with the experimental qe with the value of the coefficient of determination being 0.9996, which rendered it suitable for describing the adsorption kinetics of Pb2+ onto CMOSW. Figure 8. Pseudo-first-order and pseudo-second-order kinetics for Pb2+ removal by CMOSW. 3.5. Adsorption mechanism The lead ions covered the surface and diffused into the pores of the CMOSW adsorbent by capillary force, which was confirmed by the results of the textural properties (surface area and pore size) analysis (Ta- ble 1). Thus, the CMOSW adsorbent with better 575 A. S. Yusuff, L. T. Popoola, V. Anochie Acta Polytechnica Kinetic model Parameter values Unit Pseudo-first-order qe (exp) 1.443 mg·g−1 qe (cal) 1.337 mg·g−1 k1 0.016 min−1 R2 0.9773 – Pseudo-second-order qe (cal) 1.462 mg·g−1 k2 0.0086 g·mg−1·min R2 0.9996 – Table 4. Kinetic models and their parameters for Pb2+ adsorption onto CMOSW. textural characteristics would adsorb more lead ions. The capillary force within the mesopore facilitated the diffusion of the metal ions, which enhanced the overall adsorption capacity. Additionally, the electrostatic interaction, which occurred between the lead ions and negative functional groups (O-H and C=O) on the adsorbent surface, also aided the adsorption. There- fore, the adsorptive removal of lead ions by CMOSW involved a synergy between the capillary forces and electrostatic interactions [41]. 4. Conclusion and future recommendations This study has revealed that an adsorbent prepared from onion skin was efficient for the removal of Pb2+ from an aqueous solution. The Freundlich isotherm model provided a better fit of the equilibrium adsorp- tion data, indicating a multilayer adsorbate-adsorbent system with the dominance of the chemisorption. The maximum removal efficiency of 97.3 ± 0.01 % was achieved at an optimum adsorbent dosage of 1.4 g/L, a contact time of 120 min and pH of 6.0. The pseudo- second-order model proved to best describe the kinetic data. The change in the adsorbent structure and peak changes of the spectra after adsorption, as revealed by SEM and FTIR analyses, respectively, suggested a distinct adsorption of the Pb2+ onto CMOSW. The removal of Pb2+ by CMOSW via an adsorption pro- cess experiment led to encouraging results, and we authors wish to achieve the same breakthrough in an adsorption column mode under the conditions appli- cable to the treatment of industrial wastewater. The current investigation also revealed that CMOSW has a potential as an effective adsorbent for the toxic heavy metals and dye removal. List of symbols Co initial concentration [mg/L] Ce equilibrium concentrations [mg/L] V solution volume [L] m mass of adsorbent use [g] qe amount of metal ion adsorbed at equilibrium [mg/g] qmax maximum adsorption capacity [mg/g] b Langmuir equilibrium constant kF adsorption capacity of the adsorbent [mg/g(L/mg)1/n] n Freundlich exponent qt amount of metal ion adsorbed at time t [mg/g] k1 rate constant for pseudo-first order model [min−1] k2 rate constant for pseudo-second order model [g/mg min] Acknowledgements The authors would like to thank the Department of Chem- ical and Petroleum Engineering, Afe Babalola University, Ado-Ekiti, Nigeria for allowing us to use the laboratory facilities. References [1] C. N. Owabor, I. O. Oboh. Kinetic study and artificial neural network modeling of the adsorption of naphthalene on grafted clay. Journal of Engineering Research 17(3):41–51, 2012. [2] A. S. Yusuff, I. I. Olateju, O. A. Adesina. TiO2/anthill clay as a heterogeneous catalyst for solar photocatalytic degradation of textile wastewater: Catalyst characterization and optimization studies. Materialia 8:100484, 2019. https://doi.org/10.1016/j.mtla.2019.100484. [3] M. Rafatullah, O. Sulaiman, R. Hashimi, A. Ahmad. Adsorption of copper (II), chromium (III), nickel (II) and lead (II) ions from aqueous solutions by meranti sawdust. Journal of Hazardous Materials 170(2-3):969–977, 2009. https://doi.org/10.1016/j.jhazmat.2009.05.066. [4] M. N. M. Ibrahim, W. S. W. Ngah, M. S. Norliyana, et al. A novel agricultural waste adsorbent for the removal of lead (II) ion from aqueous solutions. Journal of Hazardous Materials 182(1-3):377–385, 2010. https://doi.org/10.1016/j.jhazmat.2010.06.044. [5] M. J. Mohammed-Ridha, A. S. Ahmed, N. N. Raoof. Investigation of the thermodynamic, kinetic and equilibrium parameters of batch biosorption of Pb (II), Cu (II), and Ni (II) from aqueous phase using low cost biosorbent. Al-Nahrain Journal for Engineering Sciences 20(1):298–310, 2017. 576 https://doi.org/10.1016/j.mtla.2019.100484 https://doi.org/10.1016/j.jhazmat.2009.05.066 https://doi.org/10.1016/j.jhazmat.2010.06.044 vol. 61 no. 4/2021 Utilization of agricultural waste adsorbent for . . . [6] S. Kavitha, R. Selvakumar, K. Swaminathan. Polyvinyl pyrrolidone K25 modified fungal biomass as biosorbent for As(V) removal from aqueous solution. Separation Science and Technology 43(15):3902–3919, 2008. https://doi.org/10.1080/01496390802222590. [7] M. A. Khan, A. Alqadami, M. Otero, et al. Heteroatom-doped magnetic hydrochar to remove post-transition and transition metal from water: synthesis, characterization and adsorption studies. Chemosphere 218:1089–1099, 2018. https: //doi.org/10.1016/j.chemosphere.2018.11.210. [8] S. Vasudevan, J. Lakshmi. Electrochemical removal of boron from water: Adsorption and thermodynamic studies. The Canadian Journal of Chemical Engineering 90:1017–1026, 2012. [9] R. Bushra, M. Shahadat, M. A. Khan, et al. Optimization of polyamiline supported Ti (IV) arsenophosphate composite cation exchanger based ion-selective membrane electrode for the determination of lead. Industrial and Engineering Chemistry Research 53(50):19387–19391, 2014. https://doi.org/10.1021/ie5034655. [10] F. Gorzin, M. M. B. R. Abadi. Adsorption of Cr (VI) from aqueous solution by adsorbent prepared from paper mill sludge: kinetics and thermodynamic studies. Adsorption Science and Technology pp. 1–21, 2017. [11] A. A. Oyekanmi, A. Z. A. Latiff, Z. Daud, et al. Adsorption of cadmium and lead from palm oil mill effluent using bone-composite: Optimization and isotherm studies. International Journal of Environmental Analytical Chemistry 99(8):707–725, 2019. https://doi.org/10.1080/03067319.2019.1607318. [12] A. S. Yusuff, I. I. Olateju, S. E. Ekanem. Equilibrium, kinetic and thermodynamic studies of the adsorption of heavy metals from aqueous solution by thermally treated quail eggshell. Journal of Environmental Science and Technology 10(5):246–257, 2017. [13] N. M. Alandis, W. Mekhamer, I. O. Aldage, et al. Adsorptive applications of montmorillonite clay for the removal of Ag (I) and Cu (II) from aqueous medium. Journal of Chemistry p. 7129014, 2019. https://doi.org/10.1155/2019/7129014. [14] N. Abdel-Ghani, M. Hefny, A. El-Chaghaby. Removal of metal ions from synthetic wastewater by adsorption onto eucalyptus camaldulensis tree leaves. Journal of Chile Chemical Society 53(3):585–589, 2008. https://doi.org/10.4067/s0717-97072008000300007. [15] S. Sugashini, K. M. M. S. Begum. Preparation of activated carbon from carbonized rice husk by ozone activation for Cr (VI) removal. New Carbon Materials 30(3):252–261, 2015. https://doi.org/10.1016/s1872-5805(15)60190-1. [16] B. H. Hameed, R. R. Krishni, S. A. Sata. A novel agricultural waste adsorbent for the removal of cationic dye from aqueous solution. Journal of Hazardous Materials 162(1):305–311, 2009. https://doi.org/10.1016/j.jhazmat.2008.05.036. [17] A. Ahmad, A. Khatoon, S. H. Mohd-Setapar, et al. Chemically oxidized pineapple fruit peel for the biosorption of heavy metals from aqueous solutions. Desalination and Water Treatment 57(14):6432–6442, 2016. https://doi.org/10.1080/19443994.2015.1005150. [18] W. Cherdchoo, S. Nithettham, J. Charoenpanich. Removal of Cr(VI) from synthetic wastewater by adsorption onto coffee ground and mixed waste tea. Chemosphere 221:758–767, 2019. https: //doi.org/10.1016/j.chemosphere.2019.01.100. [19] M. Ghasemi, A. Ghoreyshi, H. Younesi. Synthesis of a high characteristics activated carbon from walnut shell for the removal of Cr(VI) and Fe(II) from aqueous solution: Single and binary solutes adsorption. Iranian Journal of Chemical Engineering 12(4):28–51, 2015. [20] Z. Al-Othman, R. Ali, M. Naushad. Hexavalent chromium removal from aqueous medium by activated carbon prepared from peanut shell: Adsorption kinetics, equilibrium and thermodynamic studies. Chemical Engineering Journal 184:238–247, 2012. https://doi.org/10.1016/j.cej.2012.01.048. [21] A. S. Yusuff. Adsorption of hexavalent chromium from aqueous solution by Leucaena leucocephala seed pod activated carbon: Equilibrium, kinetic and thermodynamic studies. Arab Journal of Basic and Applied Sciences 26(1):89–102, 2019. https://doi.org/10.1080/25765299.2019.1567656. [22] E. O. Adeaga. Adsorption of hexavalent chromium from aqueous solution by HCl treated onion skin. Journal of Pure and Applied Science 2(1):7–13, 2017. [23] S. E. Agarry, O. O. Ogunleye, O. A. Ajani. Biosorptive removal of cadmium (II) ions from aqueous solution by chemically modified onion skin: Batch equilibrium, kinetic and thermodynamic studies. Chemical Engineering Communications 202(5):655–673, 2015. https://doi.org/10.1080/00986445.2013.863187. [24] B. W. Waweru. Efficiency and sorption capacity of unmodified and modified onion skins (Allium Cepa) to adsorb selected heavy metals from water. Kenyatta University, Nairobi, Kenya 60:1–84, 2015. [25] E. F. Olasehinde, A. V. Adegunloye, M. A. Adebayo. Cadmium (II) adsorption from aqueous solution using onion skins. Water Conservation Science and Engineering 4:175–185, 2019. https://doi.org/10.1007/s41101-019-00077-2. [26] F. P. L. Hariani, F. Riyanti, W. Sepriani. Desorption of re-adsorption of procion red MX-5B dye on alumina-activated carbon composite. Indonesian Journal of Chemistry 18(2):222–228, 2018. https://doi.org/10.22146/ijc.23927. [27] Y. H. Taufiq-yap, N. F. Abdullah, M. Basri. Biodiesel production via transesterification of palm oil using NaOH/Al2O3 catalysts. Sains Malaysiana 40(6):587–594, 2011. [28] M. D. Adetoye, S. O. Adeojo, B. F. Ajiboshin. Utilization of garlic waste as adsorbent for heavy metal removal from aqueous solution. Journal of Pure and Applied Science 6(4):6–13, 2018. [29] A. S. Yusuff, L. T. Popoola, E. O. Babatunde. Adsorption of cadmium ion from aqueous solutions by copper-based metal organic framework: equilibrium modeling and kinetic studies. Applied Water Science 9:106, 2019. 577 https://doi.org/10.1080/01496390802222590 https://doi.org/10.1016/j.chemosphere.2018.11.210 https://doi.org/10.1016/j.chemosphere.2018.11.210 https://doi.org/10.1021/ie5034655 https://doi.org/10.1080/03067319.2019.1607318 https://doi.org/10.1155/2019/7129014 https://doi.org/10.4067/s0717-97072008000300007 https://doi.org/10.1016/s1872-5805(15)60190-1 https://doi.org/10.1016/j.jhazmat.2008.05.036 https://doi.org/10.1080/19443994.2015.1005150 https://doi.org/10.1016/j.chemosphere.2019.01.100 https://doi.org/10.1016/j.chemosphere.2019.01.100 https://doi.org/10.1016/j.cej.2012.01.048 https://doi.org/10.1080/25765299.2019.1567656 https://doi.org/10.1080/00986445.2013.863187 https://doi.org/10.1007/s41101-019-00077-2 https://doi.org/10.22146/ijc.23927 A. S. Yusuff, L. T. Popoola, V. Anochie Acta Polytechnica [30] T. G. Kebede, S. Dube, A. A. Mengistie, et al. Moringa stenopetala bark: a novel green adsorbent for the removal of metal ions from industrial effluents. Physics and Chemistry of the Earth 107:45–57, 2018. https://doi.org/10.1016/j.pce.2018.08.002. [31] J. Guo, Y. Song, X. Ji, et al. Preparation and characterization of nanoporous activated carbon derived from prawn shell and its application for removal of heavy metal ions. Materials 12(2):241–247, 2019. https://doi.org/10.3390/ma12020241. [32] A. Sulaymon, S. Ebrahim, M. Ridha. Equilibrium, kinetic, and thermodynamic biosorption of Pb(II), Cu(II) and Cd(II) ions by dead anaerobic biomass from synthetic wastewater. Environmental Science and Pollution Research 20(1):175–187, 2013. [33] S. F. Lim, A. Y. W. Lee. Kinetic study on removal of heavy metal ions from aqueous solution by using soil. Environmental Science and Pollution Research 22:10144–10158, 2015. https://doi.org/10.1007/s11356-015-4203-6. [34] A. A. Alghamdi, A. Al-Odayni, W. S. Saeed, et al. Efficient adsorption of lead (II) from aqueous phase solutions using polypyrrole-based activated carbon. Materials 12(12):1–16, 2020. https://doi.org/10.3390/ma12122020. [35] M. Imamoghu, O. Tekir. Removal of copper (II) and lead (II) from aqueous solutions by adsorption on activated carbon from a new precursor hazelnut husks. Desalination 228(1-3):108–113, 2008. https://doi.org/10.1016/j.desal.2007.08.011. [36] M. S. El-Geundi, M. M. Nassar, T. E. Farrag, M. H. Ahmed. Removal of an insecticide (methomyl) from aqueous solutions using natural clay. Alexandria Engineering Journal 51(1):11–18, 2012. https://doi.org/10.1016/j.aej.2012.07.002. [37] L. Mouni, D. Merabet, A. Bouzaza, L. Belkhiri. Adsorption of Pb (II) from aqueous solutions using activated carbon developed from Apricot stone. Desalination 276(1-3):148–153, 2011. https://doi.org/10.1016/j.desal.2011.03.038. [38] M. Mohapatra, S. Khatum, S. Anand. Adsorption behaviour of Pb(II), Cd(II) and Zn(II) on NALCO plant sand. Indian Journal of Chemical Technology 16:291–300, 2009. [39] J. Bayuo, K. B. Pelig-Ba, M. A. Abukari. Optimization of adsorption of parameters for effective removal of lead (II) from aqueous solution. Physical Chemistry: An Indian Journal 14(1):1–25, 2019. [40] N. Gaur, A. Kukreja, M. Yadav, A. Tiwari. Adsorption removal of lead and arsenic from aqueous solution using soya bean as a novel biosorbent: equilibrium isotherm and thermal stability studies. Applied Water Science 8:98, 2018. https://doi.org/10.1007/s13201-018-0743-5. [41] Y. H. Zhao, J. T. Geng, J. C. Cai, Y. F. Cai. Adsorption performance of basic fuchin on alkali-activated diatomite. Adsorption Science and Technology 38(5-6):151–167, 2020. https://doi.org/10.1177/0263617420922084. 578 https://doi.org/10.1016/j.pce.2018.08.002 https://doi.org/10.3390/ma12020241 https://doi.org/10.1007/s11356-015-4203-6 https://doi.org/10.3390/ma12122020 https://doi.org/10.1016/j.desal.2007.08.011 https://doi.org/10.1016/j.aej.2012.07.002 https://doi.org/10.1016/j.desal.2011.03.038 https://doi.org/10.1007/s13201-018-0743-5 https://doi.org/10.1177/0263617420922084 Acta Polytechnica 61(4):1–9, 2021 1 Introduction 2 Methodology 2.1 Materials 2.2 Preparation and characterization of adsorbent 2.3 Adsorption experiments 2.4 Adsorption isotherm 2.5 Adsorption kinetics 3 Results and discussion 3.1 Characterization of CMOSW adsorbent 3.2 Influence of adsorption process parameters 3.2.1 Influence of initial lead ions concentration 3.2.2 Influence of contact time 3.2.3 Influence of adsorbent dosage 3.2.4 Influence of aqueous solution pH 3.3 Adsorption isotherms 3.4 Adsorption kinetics 3.5 Adsorption mechanism 4 Conclusion and future recommendations List of symbols Acknowledgements References