Effect of an industrial chemical waste on the uptake J. Serb. Chem. Soc. 87 (0) 1–14 (2022) Original scientific paper JSCS–11454 Published 30 September 2022 1 Synthesis of activated carbons from water hyacinth biomass and its application as adsorbents in water pollution control AHMAD HAKKY MOHAMMAAD* and MIRJANA KIJEVČANIN# University of Belgrade Faculty of Technology and Metallurgy, Karnegijeva 4, 11000 Belgrade, Serbia (Received 21 December 2021, revised 10 February, accepted 11 February 2022) Abstract: The water hyacinth biomass was used for the synthesis of activated carbons in a process of chemical activation with ZnCl2, followed by controlled pyrolysis. The applied impregnation weight ratios ZnCl2 and dry hyacinth bio- mass were in the range of 0.5–3.5. The carbonization was conducted at four different temperatures (400–700 °C) under an inert atmosphere. The highest yield of activated carbon was obtained for the impregnation ratio of 0.5 and carbon- ization temperature of 400 °C. The samples were characterized using elemental analysis, adsorption–desorption isotherms of nitrogen and SEM analysis. The activated carbon obtained with an impregnation ratio 2.0 and carbonization temperature of 500 °C (2.0AC500) showed the highest values of specific surface area and total pore volume of 1317 m2 g-1 and 0.697 cm3 g-1, respectively. The adsorption of glyphosate, pesticide with a strong negative environmental impact, was a fast process, with the equilibrium time of 120 min. The adsorption iso- therms were fitted with Langmuir and Freundlich model. The Langmuir ads- orption capacity of qmax = 240.8 mg g -1 for 2.0AC500 classified the selected adsorbent as a very efficient one. The tested adsorption process followed the kinetics of the pseudo-second-order model. Keywords: carbonization; characterization; pyrolysis; pesticide removal; ads- orption; modelling. INTRODUCTION One of the leading environmental problems in Africa and Asia is the pre- sence of water hyacinth (Eichhornia crassipes) in natural waters (mostly rivers and lakes). Water hyacinth forms dense and impenetrable floating mats on water surfaces, causing considerable problems in aquatic ecosystems. This plant has shown a strong negative impact on the biodiversity of the aquatic system in many * Corresponding author. E-mail: ahmadhakky59@gmail.com # Serbian Chemical Society member. https://doi.org/10.2298/JSC212121006M 2 MOHAMMAAD and KIJEVČANIN ways: its presence leads to a significant reduction in the amount of light in the water, prevents access to wildlife (birds in particular) thereby disrupting the nor- mal functioning of fauna and representing a suitable environment for mosquitoes breeding.1 Utilization of water hyacinth biomass as source of lignocellulose for the activated carbon production can be one of the strategies in water pollution con- trol. Using activated carbon obtained from lignocellulose biomass instead of fossil coal will reduce the production of greenhouse gasses and therefore repre- sents a green approach in the synthesis of materials that can be used in process of pollutant removal.2 The water hyacinth is characterized by a high content of lig- nocellulose biomass, including 48 % hemicellulose as the major component, along with 20 % cellulose and with 10 % of average lignin content, so it can be potentially employed as a proper carbon source.3–5 The activated carbons have been used as adsorbents of a wide range of con- taminants such as pharmaceuticals, metallic and non-metallic pollutants and dyes from aqueous solutions.2,6 In comparison with other adsorbents (zeolites, clays and polymers) activated carbons show better performance and stability in terms of adsorption.7 The chemical activation of raw lignocellulose precursor material is usually a one-step method for the activated carbons preparation. Among many chemical agents, the ZnCl2 is one of the most effective chemicals used for pro- ducing activated carbons with highly developed porosity.8,9 This activation agent has a high activating capability, and it is relatively expensive. In process of chemical activation, the ZnCl2 contributes to the pore development by localized decomposition of organic matter, inhibiting tar formation and enhancing the carbon yield.8,9 Water hyacinth has already been used as a precursor for activated carbon synthesis. The activation processes were dominantly performed by KOH10 or H3PO4 11 under various and well-studied experimental approach. On the other hand, ZnCl2 activation of water hyacinth has been applied, 4,12 but the impact of amount of the activation agent has not been sufficiently studied. Pesticides are chemical substances used for the increase of the agricultural production. As artificial organic compounds, pesticides can remain in the envi- ronment for many years and may be transported over a long distance.13 Among many pesticides, glyphosate-based herbicides as systemic, broad-spectrum herbi- cides are widely used, therefore contributed to concerns about their environmen- tal impact.14 International Agency for Research on Cancer and World Health Organization classify glyphosate as substance that is “probably carcinogenic to humans” (group 2A).15 According to the author’s best knowledge, there is lack in the existing literature about application of activated carbons obtained from water hyacinth bio waste as adsorbents of glyphosate. ACTIVATED CARBONS FOR GLYPHOSATE REMOVAL 3 The main objective of the present work was to obtain activated carbons with a high surface area from water hyacinth biomass, using different amounts of ZnCl2 and applying different carbonization temperatures. The selected activated carbon was further evaluated as adsorbent for glyphosate removal. EXPERIMENTAL Materials The water hyacinth (WH) plant (Karbala, Iraq) was used as raw material for obtaining the activated carbon. The raw WH was washed with distilled water. The roots and stalks without leaves were chopped and dried in an oven for 24 h. The dried WH was boiled in 0.25 M hydrochloric acid to remove metallic oxides, rinsed with distilled water, and finally dried in vacuum freeze dryer for 24h. The dry WH was crushed and ground in rotary mill, and finally sieved in order to obtain particles sized 1.4–2.0 mm. The ZnCl2 (≥98 %), supplied from Sigma–Aldrich, was used as activating agent in pro- cess of chemical activation during the activated carbons synthesis. The herbicide glyphosate – GPh (≥99 %), used in adsorption study, was purchased from Merck. Activated carbons synthesis The activated carbon (AC) based on dry water hyacinth biomass was prepared by chem- ical activation of dry WH with ZnCl2 according to the procedure described in literature. 16 The impregnation ratio was calculated as the ratio of the weight of ZnCl2 in solution to the weight of the dry WH. The impregnation ratio was 0.0, 0.5, 1.0, 1.5, 2.0, 2.5 and 3.0. The 40 g of dry WH sample was added to 150 ml of solution with the appropriate mass of ZnCl2 and stirred at 60 °C for 4 h. The solid and liquid phases were separated by filtration through Buchner funnel and dried at 105 °C during 24 h. The drying process was applied prior to carbonization in order to avoid the loss of sample caused by rash steam development. The carbonization of activated WC was carried out in electrical furnace with nitrogen flowing (150 cm3 min-1) and at heating rate of 15 °C min-1. The carbonization during 80 min was conducted at following temperatures: 400, 500, 600 and 700 °C. The obtained activated carbon was rinsed with 0.5 M HCl in order to remove the activ- ating agent, washed with hot distilled water until neutral pH and finally dried at 110 °C for 12 h. The dry samples were weighted in order to calculate the yield. The synthetized activated carbons were denoted according to impregnation ratio and carbonization temperature, e.g., 0.5AC400 means that the impregnation ratio and the carboniz- ation temperature were 0.5 and 400 °C, respectively. The yield of activated carbons was calculated from mass ratio between activated carbon and starting WH after drying process: AC dryWHAC 100 m Y m = (1) where Y / % is yield of the synthesis, mAC / g is the mass of activated carbon and mdryWH / g is the mass of dry WH. Characterization methods The synthetized ACs were characterized using elemental analysis, nitrogen adsorption- desorption isotherms and scanning electron microscopy (SEM). 4 MOHAMMAAD and KIJEVČANIN The elemental analysis was used in order to determinate the content of carbon, hydrogen, nitrogen and sulphur in raw materials and activated carbons. The analysis was performed using elemental analyser instrument (Thermo Scientific – FlashEA1112 automatic elemental analyzers). Prior to analysis, the samples were dried in an oven at 110 °C. The textural properties of activated carbons were obtained from adsorption-desorption nitrogen isotherms at –196 °C (Micromeritics’ ASAP® 2020). Prior to analysis the samples were outgassed at 110 °C during 12 h. The specific surface area (SBET) was calculated accord- ing to Brunner–Emmett–Teller method,17 the total pore volume (VT) was estimated from N2 adsorption isotherm according to Gurvich rule, and represents the liquid molar volume ads- orbed at pressure p/p0 of 0.999. 18,19 The volumes of micropores and mesopores were cal- culated using Dubinin–Radushkevich method20 and Barrett, Joyner, Halenda (BJH) method,21 respectively. The morphology of activated carbons was characterized by scanning electron micro- scopy (SEM-JEOL, JSM 6360 LV). Adsorption study The herbicide glyphosate (GPh) was used as a model of pesticide pollutant. During ads- orption study, the GPh concentration was determinated by UV–Vis spectrophotometer (UV– –Vis 1800 Shimadzu) at λmax = 264 nm. The volume of GPh solution of 75 cm3 was introduced into the glass flasks and mixed with 20 mg of adsorbents. After the adsorption process, the GPh concentration in the super- natant was analyzed, with previous separation of the solid phase by centrifugation at 12,000 rpm for 20 min. The effect of surface development of activated carbons on the adsorption efficiency was performed using GPh starting concentration of 100 mg dm-3 for the adsorption time of 240 min. The adsorption was performed from a solution with pH 3.55, which represents the unbuf- fered pH value of GPh solution for the investigated concentration. The effect of contact time on the GPh adsorption was monitored at predetermined time intervals between 5 min and 240 min, at 25 °C, with starting GPh concentration of 100 mg dm-3. The adsorption isotherms were constructed at equilibrium adsorption time at 25 °C with GPh initial concentration in range 50–250 mg dm-3. The amount of the adsorbed herbicide (qt / mg g -1) was calculated according to: ( )i t t c c V q m − = (2) where ci is the initial concentration of GPh /mg dm -3, ct / mg dm -3 is the concentration of GPh in time t, V / dm-3 is the volume of GPh solution and m / g is the mass of the adsorbent. Adsorption data analysis Two well-known isotherm models Langmuir22 and Freundlich23 were used for modelling the adsorption data, while the adsorption kinetics data were fitted with both, pseudo-first24 and pseudo-second order25 kinetics’ models. The applied isotherm and kinetics model have been frequently used for heterogeneous adsorption systems that consist of solid adsorbent and dis- solved adsorbate molecule.26 ACTIVATED CARBONS FOR GLYPHOSATE REMOVAL 5 RESULTS AND DISCUSSION Results of characterization The yield of activated carbons obtained after chemical activation with ZnCl2 and carbonization process is given in Fig. 1. Fig. 1. The influence of impregnation ratio and carbonization temperature on yield of activated carbons prepared from water hyacinth dry material. It was observed that activated carbons obtained with the impregnation ratio 0 (i.e., without applied ZnCl2) and the temperature range 400–700 °C had relat- ively low yield in the range of 19.6–24.9 %. This fact can be related to a high content of volatile matter and relatively low lignin content in raw WH material used for the preparation of activated carbons. According to the literature, the activated carbons obtained by pyrolisis without prior activation showed signific- ant weight loss attributed to gasses extraction (CO, CO2 and CH4). 27 The act- ivation agent and applied carbonization temperature have a significant impact on the yield of activated carbons (Fig. 1). Generally, the best yields were obtained for the lowest carbonization temperature (400 °C). With the temperature increase the yield of activated carbon decreased regardless the amount of applied ZnCl2, which was explained by the promotion of tar volatilization by higher tempe- rature.28 For each carbonization temperature it was observed that the amount of the activation agent has a similar impact on yield, i.e., the activated carbon yields continually decreased with the impregnation ratio higher than 0.5 (Fig. 1). This observation can be explained by larger evolution of volatiles compounds affected by dehydration agent – ZnCl2. 29 In order to estimate the effect of the amount of activation agent – ZnCl2, on surface development, the specific surface area (SBET) of samples obtained on the carbonization temperature of 400 °C was correlated with the impregnation ratio (from 0.0 to 3.0) and shown in Fig. 2. The activated carbon obtained without impregnation showed the lowest value of SBET. This result was expected since the ZnCl2 works as a dehydration reagent during the carbonization process, which leads to carbon charring, form- 6 MOHAMMAAD and KIJEVČANIN ations of the aromatic, porous structure, and restricts the formation of the tar.29 The introduction of ZnCl2 led to development of specific surface and this trend continued up to impregnation ratio 2.0, and after that decreased for higher imp- regnation ratios. These results are in accordance with literature data.27,29,30 Fig. 2. The influence of impregnation ratio (mZnCl2/mdry WH) on specific surface area of carbons obtained by carbonization at 400 °C. The more detailed textural properties analysis was applied on the activated carbon samples with impregnation ratio 2.0, since the carbons with highest SBET values (Fig. 2) were obtained using ZnCl2 in this impregnation ratio. The effect of temperature (400–700 °C) on the specific surface area (SBET), micropore (Vmic) and mesopore volume (Vmeso) as well as on total pore volume (Vtot) of the activated carbons with impregnation ratio 2.0 are presented in Table I. TABLE I. Surface area and pore volumes of activated carbons with impregnation ratio 2.0 obtained at different carbonization temperatures T / °C SBET / m 2 g-1 Vtot / cm 3 g-1 Vmic / cm 3 g-1 Vmeso / cm 3 g-1 400 1154 0.602 0.301 0.298 500 1317 0.697 0.152 0.541 600 1284 0.670 0.135 0.527 700 1163 0.605 0.113 0.485 The most of the investigated textural properties increased with the rise of final carbonization temperature from 400 to 500 °C, while further increase of temperature led to surface development decreasing. Increasing temperature from 400 to 500 °C had strong positive impact on mesoporosity development, while temperatures higher than 500 °C led to slight decrease of mesopore volume. Besides that, all investigated carbonization temperatures above 400 °C reduced microporosity of activated carbons. Similar trends can be found in litera- ture,27,28,31 According to Rodriguez-Reinoso and Molina-Sabio,27 ZnCl2 has an important role in the development of micro- and mesoporosity in the carboniz- ACTIVATED CARBONS FOR GLYPHOSATE REMOVAL 7 ation process up to 500 °C, but at higher temperatures the reaction of ZnCl2 with the char is negligible. The decrease in textural properties at temperatures higher than 500 °C can also be attributed to a sintering effect at high temperature, fol- lowed by the shrinkage of the char, and the realignment of the carbon structure.32 Sentilkumar et al.12 applied the weight of ZnCl2 that corresponded to 10 % of raw water hyacinth and the synthetized activated carbon with SBET = 579.94 m2 g–1 at high temperature of 900 °C. Boonpoke4 produced the microporous act- ivated carbon with a specific surface area of 1066 m2 g–1 at 600 °C using an equal amount of ZnCl2 and raw water hyacinth (impregnation ratio 1:1). The pre- sent study applied different amounts of ZnCl2 and found that the impregnation ratio 2:1 leads to obtaining the activated carbons with higher values of SBET than those in previous studies at lower carbonization temperatures of 400 and 500 °C (Table I). Wu et al.10 activate the raw water hyacinth with KOH and synthetized activated carbon with SBET = 1380 m 2 g–1, but on 800 °C. Yang and Qiu33 showed that the activated carbons with the specific surface area of even 2000 m2 g–1 could be produced from pharmaceutics’ herb residue, but synthesis required chemical activation with booth NaOH and ZnCl2. The elemental analysis was performed in order to evaluate the effect of tem- perature on the chemical composition of activated carbons. The result of the ele- mental analysis of dry WH and the activated carbons prepared with impregnation ratio of 2.0 are presented in Table II. TABLE II. The results of the elemental analysis Sample Content of elements, wt. % C H Oa N Ash Dry WH 41.22 6.23 47.07 1.54 3.94 AC400 80.31 3.37 15.16 0.32 0.84 AC500 81.57 3.15 14.20 0.27 0.81 AC600 83.24 2.98 12.79 0.24 0.75 AC700 84.15 2.75 12.23 0.19 0.68 aThe oxygen content is calculated from the difference up to 100 % The major organic elements in all investigated samples are carbon and oxy- gen. The WH has higher content of ash, consisting mainly of silica and metal oxides.16 The treatment with HCl after activation process led to leaching of metal cat- ions and therefore the ash content was reduced. During the carbonization process, with temperature rise the content of carbon increased, which was expected.16 The scanning electron microscopy (SEM) was employed to show the differ- ence in the morphology between the raw WH material and the activated carbons with impregnation ratio 2:1, obtained in the temperature range from 400–700 °C. 8 MOHAMMAAD and KIJEVČANIN The SEM images were recorded using magnification of 3000 and presented in Fig. 3. In Fig. 3 significant difference in surface morphology can be observed between raw WH and ACs. The surface of the raw WH is moderately developed with parts of a smooth area, but after impregnation and carbonization, the raw WH biomass turns to be more porous with more open structures (Fig. 3). The increase of the carbonization temperature led to a reduction in small cracks in the activated carbon surfaces which could be responsible for the reduce of textural properties. According to the textural analysis the mesopore formation was dom- inantly responsible for the surface development (Table I). Since the mesopores are those with diameter from 2–50 nm, they are not visible in Fig. 3, where mac- roporous structure can be noticed. Fig. 3. The SEM images of: a) raw WH; b) 2.0AC400; c) 2.0AC500; d) 2.0AC600; e) 2.0AC700. Adsorption study The effect of surface development of activated carbons on adsorption effi- ciency. The aim of this adsorption study was to select the activated carbon with the best adsorption properties toward GPh. The effect of surface development of the activated carbons (impregnation ratio 2.0, Tcarb = 400 to 700 °C) on the amount of adsorbed GPh for 240 min is presented in Fig. 4. Although the specific surface area shows an impact on the amount of the adsorbed GPh, the difference in q240 for the samples with relatively close values ACTIVATED CARBONS FOR GLYPHOSATE REMOVAL 9 of SBET was negligible. For example, the samples with SBET values of 1317 and 1284 m2g–1 adsorbed almost the same amount of GPh with values 153 and 151 mg g–1, respectively. The obtained results suggested that the increasing SBET values of ~30 m2 g–1 did not lead to a significant increase in the efficiency of GPh removal. Herath et al34 found that both physisorption and chemisorption mechanisms affected the adsorption of glyphosate onto the activated carbon, but that physical interactions dominantly increase with the rise of surface develop- ment. Fig. 4. The influence of specific surface area (SBET) on the amount of the adsorbed glyphosate (q240) for 240 min. Although 2.0AC500 and 2.0AC600 showed almost the same amount of ads- orbed GPh for the adsorption time of 240 min, the 2.0AC500 was selected for further adsorption study, since its synthesis requires lower carbonization tempe- rature. Kinetic study The effect of contact time on GPh adsorption on selected adsorbent 2.0AC500 was performed in order to estimate the equilibrium time of adsorption (Fig. 5). The uptake of GPh increased gradually up to 120 min and after this time the amount of adsorbed GPh was almost constant. For the investigated process, the time of 120 min can be considered as equilibrium, since there is no significant change in the amount of the adsorbed GPh for longer times. The amount of ads- orbed GPh in equilibrium time was found to be qe = 151.87 mg g –1. In order to describe the kinetics of the process, the experimental data (Fig. 5) were fitted with pseudo-first and pseudo-second-order kinetic models. The calculated kinetic parameters for both models are given in Table III. The results presented in Table III revealed that the experimental data show better fit with pseudo-second order kinetic model than with pseudo-first order model. The amount of adsorbed GPh in equilibrium calculated from pseudo-sec- 10 MOHAMMAAD and KIJEVČANIN ond order kinetic model was qe = 156.3 mg g –1 which is very close to the experi- mental value of qe = 151.87 mg g –1. According to many authors, pseudo-second order model indicates that the possible mechanism of investigated process inc- luded chemisorption of pollutants on adsorbent surface.35 Fig. 5. The effect of contact time on GPh adsorption using activated carbon 2.0AC500. TABLE III. The parameters of pseudo-first and pseudo–second order kinetic models Pseudo-first order qe / mg g -1 k1 / min -1 R2 214.9 0.0773 0.944 Pseudo-second order qe / mg g -1 k2 / g mg -1 min R2 156.3 0.0011 0.994 Adsorption isotherm models The experimental isotherm data together with nonlinear fits of Langmuir and Freundlich models are presented in Fig. 6, while the calculated isotherm’s para- meters are listed in Table IV. Fig. 6. The adsorption isotherm for GPh adsorption on 2.0AC500 on 25 °C, fitted with Langmuir and Freundlich isotherm model. ACTIVATED CARBONS FOR GLYPHOSATE REMOVAL 11 Table IV. Calculated isotherm parameters for Langmuir and Freundlich model for GPh ads- orption on 2.0AC500 Langmuir KL / dm 3 mg-1 qmax / mg g -1 R2 0.0284 240.8 0.995 Freundlich KF / (mg g -1)(dm3 mg-1)1/n n R2 41.15 3.23 0.965 Both investigated models generally could be applied to describe the GPh adsorption onto 2.0AC500 process, since coefficients of determination are R 2 > > 0.900 (Table IV). However, the Langmuir model showed better fitting with the experimental data, having R2 = 0.995. The agreement of adsorption data with Langmuir model indicated that surface of investigated adsorbent is energetically homogenous and the binding sites are uniformly distributed with the same affi- nity. The adsorption process occurs until monolayer surface coverage and after saturation there is no additional interaction between adsorbate molecules. The monolayer adsorption capacity (qmax) according to the Langmuir model was 240.8 mg g–1. The literature review of glyphosate adsorption on carbons derived from different type of biomass and other adsorbents is presented in Table V. TABLE V. Comparison of glyphosate adsorption capacity of different adsorbents Adsorbent Adsorption parmeters qmax / mg g -1 References 2.0AC500 SBET = 1317 m 2 g-1;pH 3.55; T = 25 °C, CGPh, 50–250 mg dm -3 240.8 Current study Rice husk char SBET = 229 m 2 g-1; pH < 4; CGPh, 0–100 mg dm -3 123.03 34 Carbon derived from waste newspapers SBET = 535 m 2 g-1;pH 2.5; T = 28 °C; CGPh, 5–100 mg dm -3 48.4 36 Eucalyptus camaldulensis bark‑mediatedchar pH 10.18, CGPh = 20.28 mg L -1, contact time 78.42 min; T = 303.23 K 66.76 37 Carbon obtained from sugar cane bagasse CGPh, 0.338–2.704 g L -1 161.3 38 Zr-MOF pH 3–6; CGPh, 20–70 mg L -1; contact time: 1–180 min, T, 308–3018 K 256.54 39 Resin D301 T, 303.15–318.15 K; CGPh, 5–50 mg/L; pH 4 833.33 40 Although Chen et al.40 found that Resin D301 as adsorbent showed extra- ordinary efficiency for glyphosate removal, the adsorption capacity for 2.0AC500 of 240.8 mg g–1 is close to the adsorption capacity of Zr–MOF adsorbent39 and still higher than qmax of the most reported carbon-based adsorbents. Therefore the 2.0AC500 could be classified as efficient and tested in real wastewaters treat- ments. 12 MOHAMMAAD and KIJEVČANIN CONCLUSION The water hyacinth biomass was used as starting material for the production of activated carbons. The activated carbons were synthetized using chemical act- ivation with ZnCl2 followed by controlled carbonization. On carbonization at various carbonization temperatures: 400, 500, 600 and 700 °C the different imp- regnation ratios of ZnCl2 in range of 0.5–3.5 were applied. The chosen synthesis parameters showed significant impact on activated carbons yield and surface development. The impregnation ratio of 0.5 and temperature of 400 °C led to the highest yield of activated carbons. On the other hand, the textural properties showed that the most developed surface of 1317 m2 g–1 and the total pore vol- ume of 0.697 cm3 g–1 has the activated carbon obtained with the impregnation ratio 2.0 and the carbonization temperature of 500 °C. This activated carbon with the best textural properties was used as an adsorbent for glyphosate, pesticide with strong negative environmental impact. Experiments showed that the ads- orption takes place very fast and the equilibrium time was estimated at 120 min. The adsorption isotherms were fitted with Langmuir and Freundlich model, and Langmuir model showed better fit indicating that adsorption occurs in the form of monolayer on energetically equal and homogenously distributed adsorption sites. The Langmuir adsorption capacity of qmax=240.8 mg g –1 classified selected adsorbent as very efficient one. The adsorption kinetics study revealed that gly- phosate adsorption follows the pseudo-second order kinetics, which indicates possible chemisorption mechanism. И З В О Д СИНТЕЗА АКТИВНОГ УГЉА ИЗ БИОМАСЕ ВОДЕНОГ ЗУМБУЛА И ЊЕГОВА ПРИМЕНА КАО АДСОРБЕНАТА У КОНТРОЛИ ЗАГАЂЕЊА ВОДЕ AHMAD HAKKY MOHAMMAAD и МИРЈАНА КИЈЕВЧАНИН Универзитет у Београду Технолошко–металуршки факултет, Карнегијева 4, 11000 Београд Биомаса воденог зумбула је коришћена за синтезу активног угља у процесу хемиј- ске активације са ZnCl2, након чега је уследила контролисана пиролиза. Примењени масени односи импрегнације ZnCl2 и суве биомасе зумбула били су у распону од 0,5–3,5. Карбонизација је спроведена на четири различите температуре (400–700 C) у инертној атмосфери. Највећи принос активног угља добијен је за однос импрегнације 0,5 и тем- пературу карбонизације 400 C. Узорци су карактерисани применом елементалне анализе, адсорпционо–десорпционих изотерми азота и СЕМ анализе. Активни угаљ добијен за однос импрегнације 2,0 и температуру карбонизације 500 C (2.0AC500) показао је вредности специфичне површине и укупне запремине пора од 1317 и 0,697 cm3 g-1, редом. Адсорпција глифосата, пестицида са јаким негативним утицајем на жи- вотну средину, била је брз процес, са равнотежним временом од 120 min. Изотерме адсорпције су корелисане Langmuir и Freundlich моделом. Langmuir адсорпциони капа- цитет qmax = 240,8 mg g-1 за 2.0AC500 класификовао је одабрани адсорбент као веома ефикасан. Тестирани процес адсорпције пратио је кинетику модела псеудо-другог реда. (Примљено 21. децембра 2021, ревидирано 10. фебруара, прихваћено 11. фебруара 2022) ACTIVATED CARBONS FOR GLYPHOSATE REMOVAL 13 REFERENCES 1. M. A. Bote, V. R. Naik, K. B. Jagadeeshgouda, Mater. Sci. Energy Technol. 3 (2020) 397 (https://doi.org/10.1016/j.mset.2020.02.003) 2. M. Bilal, J. Ali, N. Hussain, M. Umar, S. Shujah, D. Ahmad, J. Serb. Chem. Soc. 85 (2020) 265 (https://doi.org/10.2298/JSC181108001B) 3. A. Saning, S. Herou, D. Dechtrirat, C. Ieosakulrat, P. Pakawatpanurut, S. Kaowphong, C. Thanachayanont, M. M. Titirici, L. Chuenchom, RSC Adv. 9 (2019) 24248 (https://doi.org/10.1039/C9RA03873F) 4. A. Boonpoke, J. Environ. Biol. 36 (2015) 1143 (http://www.jeb.co.in/journal_issues/2015 09_sep15/paper_15.pdf) 5. C. A. Riyanto, E. Prabalaras, J. Phys.: Conf. Ser. 1307 (2019) 012002 (https://doi.org/ 10.1088/1742-6596/1307/1/012002) 6. M. I. Din, S. Ashraf, A. Intisar, Sci. Prog. 100 (2017) 299 (https://doi.org/10.3184/00368 5017X14967570531606) 7. A. Regti, M. R. Laamari, S. E. Stiriba, M. El-Haddad, J. Assoc. Arab Univ. Basic Appl. Sci. 24 (2017) 10 (https://doi.org/10.1016/j.jaubas.2017.01.003) 8. Z. Hu, M. P. Srinivasan, Micropor. Mesopor. Mater. 43 (2001) 267 (https://doi.org/ 10.1016/S1387-1811(00)00355-3) 9. Z. Yue, J. Economy, Micropor.Mesopor. Mater. 96 (2006) 314 (https://doi.org/10.1016/ j.micromeso.2006.07.025) 10. K. Wu, B. Gao, J. Su, X. Peng, X. Zhang, J. Fu, P. K. Chu, RSC Adv. 6 (2016) 29996 (https://doi.org/10.1039/C5RA25098F ) 11. Y. Huang, L. Shunxing, C. Jianhua, Z. Xueliang, C. Yiping, Appl. Surf. Sci. 293 (2014) 160 (https://doi.org/10.1016/j.apsusc.2013.12.123) 12. S. T. Senthilkumar, R. Kalai Selvan, Y. S. Lee, J. S. Melo, J. Mater. Chem., A 1 (2013) 1086 (https://doi.org/10.1039/c2ta00210h1086) 13. M. T. Scholtz, E. Voldner, A. C. McMillan, B. J. Van Heyst, Atmos. Environ. 36 (2002) 5005 (https://doi.org/10.1016/S1352-2310(02)00570-8) 14. M. Schweizer, K. Brilisauer, R. Triebskorn, K. Forchhammer, H. R. Köhler, Peer J. 7 (2019) 7094 (https://doi.org/10.7717/peerj.7094) 15. W. Morley, S. Seneff, Surg. Neurol. Int. 5 (2014) 134731 (https://doi.org/10.4103/2152- 7806.134731) 16. T. H. Liou, Chem. Eng. J. 158 (2010) 129 (https://doi.org/10.1016/j.cej.2009.12.016) 17. J. Rouquerol, P. Llewellyn, F. Rouquerol, Stud. Surf. Sci. Catal. 160 (2007) 49 (https://doi.org/10.1016/S0167-2991(07)80008-5) 18. S. J. Gregg, K. S. W. Sing, Adsorption, Surface Area, and Porosity 2, Academic Press, London, 1982, pp. 41–105 (https://doi.org/10.1002/bbpc.19820861019) 19. F. Rouquerol, J. Rouquerol, K. Sing, Absorption by powders and porous solids, Principles, Methodology and Applications, Academic press, London, 1999, pp. 165–189 (https://doi.org/10.1016/B978-0-12-598920-6.X5000-3) 20. M. M. Dubinin, J. Colloid Interface Sci. 23 (1967) 487 (https://doi.org/10.1016/0021- 9797(67)90195-6) 21. E. P. Barrett, L. G. Joyner, P. P. Halenda, J. Am. Chem. Soc. 73 (1951) 373 (https://doi.org/10.1021/ja01145a126) 22. I. Langmuir, J. Am. Chem. Soc. 40 (1918)1361 (https://doi.org/10.1021/ja02242a004) https://doi.org/10.1016/j.mset.2020.02.003 https://doi.org/10.2298/JSC181108001B https://doi.org/10.1039/C9RA03873F https://www.researchgate.net/profile/Anusorn_Boonpoke2 https://doi.org/10.1088/1742-6596/1307/1/012002 https://doi.org/10.1088/1742-6596/1307/1/012002 http://dx.doi.org/10.3184/003685017X14967570531606 http://dx.doi.org/10.3184/003685017X14967570531606 https://doi.org/10.1016/j.jaubas.2017.01.003 https://doi.org/10.1016/j.micromeso.2006.07.025 https://doi.org/10.1016/j.micromeso.2006.07.025 https://doi.org/10.1039/C5RA25098F https://doi.org/10.1016/j.apsusc.2013.12.123 https://doi.org/10.1039/c2ta00210h1086 https://doi.org/10.1016/S1352-2310(02)00570-8 https://doi.org/10.7717/peerj.7094 https://doi.org/10.4103/2152-7806.134731 https://doi.org/10.4103/2152-7806.134731 https://doi.org/10.1016/j.cej.2009.12.016 http://dx.doi.org/10.1016/S0167-2991(07)80008-5 https://doi.org/10.1002/bbpc.19820861019 https://doi.org/10.1016/B978-0-12-598920-6.X5000-3 https://doi.org/10.1016/0021-9797(67)90195-6 https://doi.org/10.1016/0021-9797(67)90195-6 https://doi.org/10.1021/ja01145a126 https://doi.org/10.1021/ja02242a004 14 MOHAMMAAD and KIJEVČANIN 23. H. M. F. Freundlich, Z. Phys. Chem. A 57 (1906) 385 (https://doi.org/10.1515/zpch-1907- 5723) 24. S. Lagergren, Handlingar 24 (1898) 1 (https://doi.org/10.1002/andp.18983000208) 25. Y. S. Ho, J. C. Y. Ng, G. McKay, Sep. Purif. Meth. 29 (2000) 189 (https://doi.org/ 10.1081/SPM-100100009) 26. A. Ivanovska, L. Pavun, B. Dojčinović, M. Kostić, J. Serb. Chem. Soc. 86 (2021) 885 (https://doi.org/10.2298/JSC210209030I) 27. F. Rodriguez-Reinoso, M. Molina-Sabio, Coloids Surfaces, A 241 (2004) 15 (https://doi.org/10.1016/j.colsurfa.2004.04.007) 28. Q. Qian, M. Machida, H. Tatsumoto, Bioresour. Technol. 98 (2007) 353 (https://doi.org/ 10.1016/j.biortech.2005.12.023) 29. 29. S. Yorgun, N. Vural, H. Demiral, Micropor. Mesopor. Mater. 122 (2009) 189 (https://doi.org/10.1016/j.micromeso.2009.02.032) 30. A. C. Lua, T. Yang, J. Colloid Interf. Sci. 290 (2005)505 (https://doi.org/10.1016/ j.jcis.2005.04.063) 31. M. M. Gómez-Tamayo, A. Macías-García, M. A. Díez, E. M. Cuerda-Correa, J. Hazard. Mater. 153 (2008) 28 (https://doi.org/10.1016/j.jhazmat.2007.08.012) 32. K. Mohanty, D. Das, M. N. Biswas, Adsorption 12 (2006) 119 (https://doi.org/10.1007/ s10450-006-0374-2) 33. J. Yang, K. Qiu, Chem. Eng. J. 167 (2011) 148 (https://doi.org/10.1016/j.cej.2010. 12.013) 34. I. Herath, P. Kumarathilaka, M. I. Al-Wabel, A. Abduljabbar, M. Ahmad, A. R. A. Usman, M. Vithanage, Micropor. Mesopor. Mater. 225 (2016) 280 (https://doi.org/10.1016/j.micromeso.2016.01.017) 35. B. H. Hameed, R. R. Krishni, S. A. Sata, J. Hazard. Mater. 162 (2009) 305 (https://doi.org/10.1016/j.jhazmat.2008.05.036) 36. M. M. Nourouzi, T. G. Chuah, T. S. Y. Choong, Desalin. Water Treat. 24 (2010) 321 (https://doi.org/10.5004/dwt.2010.1461) 37. K. Sen, J. K. Datta, N. K. Mondal, Appl. Water Sci. 9 (2019) 162 (https://doi.org/10.1007/ s13201-019-1036-3) 38. D. C. Nguyena, A. I. Vezentseva, P. V. Sokolovskiyc, A. A. Greishc, Russ. J. Phys. Chem., A 95 (2021) 1212 (https://doi.org/10.1134/S0036024421060194) 39. Q. Yang, J. Wang, X. Chen, W. Yang, H. Pei, N. Hu, Y. Li, Y. Suo, T. Lic, J. Wang, J. Mater. Chem. 6 (2018) 2184 (https://doi.org/10.1039/C7TA08399H) 40. F. Chen, C. Zhou, G. Li, F. Peng, Arab. J. Chem. 9 (2016) S1665 (https://doi.org/ 10.1016/j.arabjc.2012.04.014). https://doi.org/10.1515/zpch-1907-5723 https://doi.org/10.1515/zpch-1907-5723 https://doi.org/10.1002/andp.18983000208 https://doi.org/10.1081/SPM-100100009 https://doi.org/10.1081/SPM-100100009 https://doi.org/10.2298/JSC210209030I https://doi.org/10.1016/j.colsurfa.2004.04.007 https://doi.org/10.1016/j.biortech.2005.12.023 https://doi.org/10.1016/j.biortech.2005.12.023 http://dx.doi.org/10.1016/j.micromeso.2009.02.032 https://doi.org/10.1016/j.jcis.2005.04.063 https://doi.org/10.1016/j.jcis.2005.04.063 https://doi.org/10.1016/j.jhazmat.2007.08.012 https://doi.org/10.1007/s10450-006-0374-2 https://doi.org/10.1007/s10450-006-0374-2 https://doi.org/10.1016/‌j.cej.2010.‌12.013 https://doi.org/10.1016/‌j.cej.2010.‌12.013 https://doi.org/10.1016/j.micromeso.2016.01.017 https://doi.org/10.1016/j.jhazmat.2008.05.036 https://doi.org/10.5004/dwt.2010.1461 https://doi.org/10.1016/j.jhazmat.2008.05.036 https://doi.org/10.1039/C7TA08399H https://doi.org/‌10.1016/j.arabjc.2012.04.014 https://doi.org/‌10.1016/j.arabjc.2012.04.014