Journal of Multidisciplinary Applied Natural Science ACCEPTED MANUSCRIPT • OPEN ACCESS The Utilization of Pectin as Natural Coagulant-Aid in Congo Red Dye Removal To cite this article before publication: F. M. K. Haryanto, A. V. M. Rumondor, H. Kristianto, S. Prasetyo, and A. K. Sugih. (2023). J. Multidiscip. Appl. Nat. Sci. in press. https://doi.org/10.47352/jmans.2774-3047.179. Manuscript version: Accepted Manuscript Accepted Manuscript is “the version of the article accepted for publication including all changes made as a result of the peer review process, and which may also include the addition to the article by Pandawa Institute of a header, an article ID, a cover sheet and/or an ‘Accepted Manuscript’ watermark, but excluding any other editing, typesetting or other changes made by Pandawa Institute and/or its licensors” This Accepted Manuscript is © 2023 The Author(s). Published by Pandawa Institute As the Version of Record of this article is going to be / has been published on a gold open access basis under a CC BY 4.0 International License, this Accepted Manuscript is available for reuse under a CC BY 4.0 International License immediately. Everyone is permitted to use all or part of the original content in this article, provided that they adhere to all the terms of the license https://creativecommons.org/licenses/by/4.0/. Although reasonable endeavors have been taken to obtain all necessary permissions from third parties to include their copyrighted content within this article, their full citation and copyright line may not be present in this Accepted Manuscript version. Before using any content from this article, please refer to the Version of Record on Pandawa Institute once published for full citation and copyright details, as permissions may be required. All third-party content is fully copyright protected and is not published on a gold open access basis under a CC BY license, unless that is specifically stated in the figure caption in the Version of Record. View the article online for updates and enhancements. https://doi.org/10.47352/jmans.2774-3047.179 https://creativecommons.org/licenses/by/4.0/ https://doi.org/10.47352/jmans.2774-3047.179 The Utilization of Pectin as Natural Coagulant-Aid in 1 Congo Red Dye Removal 2 3 Felicia M K Haryanto1); Andranyssa V M Rumondor1); Hans Kristianto1,*); 4 Susiana Prasetyo1); Asaf K Sugih1) 5 6 1 Department of Chemical Engineering, Parahyangan Catholic University, Bandung-40141 7 (Indonesia) 8 *Correspondence: hans.kristianto@unpar.ac.id 9 10 ORCIDs: 11 First AUTHOR : https://orcid.org/0000-0003-4148-6097 12 Second AUTHOR : https://orcid.org/0000-0002-0017-5623 13 Third AUTHOR : https://orcid.org/0000-0003-4747-4361 14 Fourth AUTHOR : https://orcid.org/0000-0001-5839-0054 15 Fifth AUTHOR : https://orcid.org/0000-0003-0478-540X 16 17 ACKNOWLEDGEMENT 18 19 This study is funded by Parahyangan Catholic University’s Centre of Research and 20 Community Service with contract No III/LPPM/2023-02/27-P. The authors are thankful for the 21 funding given. 22 23 AUTHOR CONTRIBUTIONS 24 25 Conceptualization, methodology, investigation, writing – original draft: FMKH, AVMR. 26 Both authors contributed equally to this work. Resources, writing – review & editing, 27 supervision, funding acquisition: HK, SP, and AKS. 28 29 CONFLICT OF INTEREST 30 31 The authors declare no conflict of interest. 32 33 34 A CC EP TE D M A N U SC RI PT mailto:hans.kristianto@unpar.ac.id https://orcid.org/0000-0003-4148-6097 https://orcid.org/0000-0002-0017-5623 https://orcid.org/0000-0003-4747-4361 https://orcid.org/0000-0001-5839-0054 https://orcid.org/0000-0003-0478-540X The Utilization of Pectin as Natural Coagulant-Aid in 1 Congo Red Dye Removal 2 3 Abstract. Coagulation using inorganic compounds such as aluminum sulfate is commonly 4 used in water-wastewater treatment. However, there are some drawbacks to its utilization, such 5 as a significant decrease in the treated water’s pH, non-biodegradable sludge, and a potential 6 negative impact on human mental health (dementia and Alzheimer's). The use of inorganic 7 coagulants can be minimized with the addition of natural-based coagulant-aid such as pectin. 8 In this study, Congo red solution, a model dye substance, was coagulated by varying the pH 9 (3–7) using alum coagulant to determine the best pH for coagulation. At the best pH, pectin 10 was introduced at various doses (0–30 mg/L), and subsequently various dye concentrations 11 (50–100 mg/L). The effect of pectin as coagulant-aid was compared with aluminum sulfate and 12 pectin only; with a response of %removal and sludge volume. It was found that the Congo red 13 dye coagulation had the best %removal at pH 6 indicating a charge neutralization mechanism. 14 The addition of 15 mg/L pectin at an aluminum sulfate dose of 30 mg/L resulted in 97.7% dye 15 removal with a sludge volume of 14 mL/L at a Congo red concentration of 50 mg/L. This value 16 is higher compared to those of aluminum sulfate and pectin only which gave 75.6 and 3.19% 17 removals, respectively. Furthermore, the addition of pectin as a natural coagulant-aid could 18 halve the sludge volume due to the formation of denser flocs. The results show a promising 19 potential of pectin as a natural coagulant-aid in water-wastewater treatment. 20 21 Keywords: Congo red, coagulant-aid, natural coagulant, pectin 22 23 1. INTRODUCTION 24 25 Coagulation and flocculation are the most commonly used methods for water and 26 wastewater treatment due to their high efficiency and low cost [1]. Furthermore, inorganic 27 coagulants such as alum (Al2(SO4)3), FeCl3, and PAC (poly(aluminum chloride)) are widely 28 used due to their ability to reduce color intensity, organic content and turbidity [2]. Aside from 29 its high efficiency, the use of inorganic coagulants has several limitations, including lowering 30 water alkalinity, producing large amounts of sludge, and the possibility of adverse effects on 31 A CC EP TE D M A N U SC RI PT both human health and the environment [3]. As a result, natural-based coagulants have been 1 explored as an alternative to reduce or substitute the use of inorganic coagulants. 2 Natural coagulants could be classified as protein, polysaccharide, or polyphenol, based 3 on their active coagulating agent [4]. Protein-based coagulant that comes from beans and 4 legume extract has been extensively studied. However, the extraction and purification steps 5 turned out to form a hindrance to its wide application and commercialization [3]. On the other 6 hand, polyphenol-based coagulant has also been investigated. Even so, the amount of research 7 is relatively limited, thus more investigation in the future is needed [5]. Lastly, polysaccharide 8 is known as the most abundant polymer found in nature [6], making it an interesting source to 9 be employed as natural coagulant. 10 Previous studies have utilized various polysaccharide sources as natural coagulants, such 11 as starch, gum, chitosan, and the like. Starch from rice, sago, and corn has been explored as 12 natural coagulant to treat textile wastewater, landfill leachate, and agro-industrial wastewater 13 [7]-[10]. This starch gave a good coagulation performance. However, the utilization of starch 14 from food sources poses a potential conflict of interest, thus limiting its commercial application 15 [11]. Gum from various sources also has been utilized as natural coagulant and coagulant-aid 16 [12]-[15]. Fruit industrial waste is an alternative non-food source that can be considered for 17 use in the application as well. This fruit waste which is commonly generated as agricultural 18 byproduct has a high potential for various applications due to its various compounds [16]. This 19 waste contains active ingredients in the form of polysaccharides such as pectin and starch, 20 which have shown their potential as coagulant and coagulant-aid [17][18]. 21 Compared to starch, pectin is a good alternative as coagulant-aid because pectin can be 22 used as it is, without any modification needed. Pectin has also been commercialized and widely 23 used for various applications such as food additives [19], medical applications [20], and 24 nutraceuticals [21]. Pectin is a heteropolysaccharide structure that is composed of α-D-(1,4) 25 galacturonan and rhamnogalacturonan with branches consisting of neutral sugar such as 26 rhamnose, arabinose, galactose, and xylose [22]. Moreover, pectin can be differentiated as high 27 and low-methoxy pectin, based on the degree of esterification. High-methoxy pectin with a 28 degree of esterification of over 50% can be made to interact with sugar to form gels, and is 29 commonly used in jam-making [23]. On the other hand, low-methoxy pectin has a degree of 30 esterification lower than 50%. It can interact with multivalent cations via the egg box model 31 [23], making it suitable for application as coagulant-aid. 32 Furthermore, compared to synthetic polymers, the utilization of pectin could become a 33 good alternative due to its highly biodegradable and non-toxic properties. For example, 34 A CC EP TE D M A N U SC RI PT polyacrylamide and acrylamide copolymers (anionic polymers) are commonly used as 1 flocculant with a high molecular weight, being very stable, readily soluble in water, and very 2 effective at a low dosage. However, this polymer is hardly biodegradable with a concern of the 3 polymer and monomer’s toxicity [24]. Another example is poly(diallydimethylammonium 4 chloride) (polyDADMAC), a cationic polymer, was proven to be chronically toxic to 5 Ceriodaphnia dubia [25], emphasizing the toxicity of synthetic polymer to aquatic organisms 6 and the ecosystem. 7 Previously, pectin had been used as a coagulant or coagulant-aid to remove heavy metals 8 [26] and turbidity [27][28] in synthetic wastewater. However, to the best of the authors’ 9 knowledge, the study of pectin as coagulant-aid to treat synthetic dye wastewater has never 10 been investigated. In this study, the application of low-methoxy pectin as a coagulant-aid and 11 alum has been used to treat synthetic Congo red as a model wastewater. Several variables that 12 influence the coagulation, such as pH, coagulant-aid dosage, and dye concentration have also 13 been examined. 14 15 2. MATERIALS AND METHOD 16 17 2.1. Materials. Congo red dye was obtained from Sigma-Aldrich, while alum (technical 18 grade) and low-methoxy pectin (food grade) was purchased from a local shop in Bandung, 19 West Java, Indonesia. All chemicals were used as obtained, without any further treatment. The 20 general properties of Congo red and pectin are presented in Table 1. 21 22 Table 1. General properties of Congo red and pectin 23 Properties Congo red Pectin Molecular formula C32H22N6Na2O6S2 C6H10O7 (monomer) Molecular weight (g/mol) 696.7 g/mol 194.1 (monomer) Molecular structure 24 n O O H H H O OH H OH H O - O H H H H OH H O OH O O CH 3 A CC EP TE D M A N U SC RI PT 2.2. Jar test experiment. The coagulation study of Congo red was conducted by using a 1 jar test apparatus. A stock Congo red solution (1 g/L) was prepared and subsequently diluted 2 using distilled water to obtain the desired Congo red concentration. The variations of 3 coagulation study are presented in Table 2. The initial pH of the solution was adjusted by using 4 0.1 M HCl or NaOH and measured by using a calibrated pH meter (Lutron ph-208). The 5 coagulation was accomplished by mixing Congo red, alum and followed by pectin solutions at 6 rapid mixing (200 rpm, 2 min), followed by slow mixing (40 rpm, 20 min), and settling for 1 7 h. The initial (Ci; mg/L) and final (Cf; mg/L) concentrations of Congo red were measured using 8 a visible spectrophotometer (Thermoscientific Genesys 30) at its maximum wavelength (510 9 nm). The removal percentage (%removal) was calculated using Equation 1. Furthermore, the 10 sludge volume (mL/L) was measured using an Imhoff cone after 1 h of settling and calculated 11 using Equation 2. All experiments were carried out in duplicate and standard deviations as 12 provided in each figure, where applicable. 13 14 % 𝑟𝑒𝑚𝑜𝑣𝑎𝑙 = (𝐶𝑖−𝐶𝑓) 𝐶𝑓 × 100% (1) 15 16 𝑠𝑙𝑢𝑑𝑔𝑒 𝑣𝑜𝑙𝑢𝑚𝑒 ( 𝑚𝐿 𝐿 ) = 𝑉 𝑠𝑙𝑢𝑑𝑔𝑒 (𝑚𝐿) 𝑉 𝑤𝑎𝑠𝑡𝑒𝑤𝑎𝑡𝑒𝑟 (𝐿) (2) 17 18 Table 2. Variations applied in this study 19 Variations pH Alum dose (mg/L) Pectin dose (mg/L) Congo red concentration (mg/L) pH study 3, 4, 5, 6, 7 50 0 50 Coagulant-aid study Best pH 30 0, 5, 10, 15, 20, 25, 30 50 Initial Congo red concentration Best pH 30 Best pectin dose 50, 60, 70, 80, 90, 100 30 0 0 Best pectin dose 20 3. RESULTS AND DISCUSSION 21 22 3.1. The effect of pH levels on coagulation. The profile of Congo red dye concentration 23 and sludge volume in coagulation was observed at different pH variations (3, 4, 5, 6, and 7) 24 A CC EP TE D M A N U SC RI PT with the coagulant dose and Congo red dye concentration fixed at 50 mg/L. The obtained results 1 are shown in Figure 1 below. It can be observed in Figure 1 that with the increase of pH, the 2 Congo red removal also increased until pH 6, before decreasing at pH 7. The highest %removal 3 was obtained at the initial pH of 6 with 92% and a sludge volume of 20 mL/L. In the pH range 4 of 3–6, the Congo red would be positively charged, as the Congo red zero charge is around pH 5 2. Furthermore, around pH 5 and 6, most of the soluble alum species were in the form of Al3+, 6 AlOH2+ and Al(OH)2+ [29] which could neutralize the negatively charged Congo red 7 molecules. With the dye molecule’s neutral charge, the electrostatic repulsion decreases, 8 allowing the formation of flocs. A further increase in pH resulted in hydrolyzation of the alum, 9 forming Al(OH)3 and Al(OH)4- while decreasing the positively charged alum species, thus 10 preventing charge neutralization to occur [30]. This reduces the dye’s coagulation efficiency 11 at pH 7, resulting in a decrease in sludge volume as well. The result obtained in this study is 12 similar to previous research studies that reported that the best performance of alum coagulation 13 was achieved at pH 6 [31]-[33]. 14 3 4 5 6 7 0 10 20 30 40 50 60 70 80 90 100 110 % removal sludge volume pH % r e m o v a l -10 0 10 20 30 40 50 60 70 80 S lu d g e v o lu m e ( m L /L ) 15 Figure 1. Effect of pH on %removal and sludge volume 16 17 3.2. The effect of coagulant-aid dose on coagulation. The effect of the coagulant-aid dose 18 on the %removal of Congo red is presented in Figure 2. The dose of coagulant-aid was varied 19 A CC EP TE D M A N U SC RI PT with the dye concentration fixed at 50 mg/L and the alum dose at 30 mg/L. The amount of alum 1 used in this variation was decreased to 30 mg/L in order to observe the significance of the role 2 pectin plays as a coagulant-aid. It may be observed that an increase in Congo red removal 3 occurred with the addition of pectin until 15 mg/L which gave a 97.0% removal; compared to 4 alum which only gave a 76.0% removal. Further addition of pectin did not increase the 5 %removal of Congo red. 6 This result clearly indicates that pectin as a coagulant-aid works synergistically with alum 7 in supporting the floc formation. This is closely related to the complex formation that occurs 8 between pectin with small flocs formed previously from the interaction of Congo red and alum. 9 Coagulation that occurs between the alum coagulant and Congo with a charge neutralization 10 mechanism will produce small flocs [34]. Pectin which is subsequently added as a coagulant-11 aid could act as a particle bridge that helps the formation of larger flocs, resulting in higher 12 coagulation performance. The amount of pectin that was gradually raised until it was over the 13 optimal level did not give a significant increase in the %removal, instead a slight decrease of 14 %removal and increase sludge volume was observed. This is possible due to the over-addition 15 of pectin that could lead to an increase of zeta potential, making a smaller floc formation [35]. 16 In turn, this could lead to more porous and voluminous sludge. Similar observations have been 17 reported by previous researchers [15][36][37]. 18 0 5 10 15 20 25 30 0 20 40 60 80 100 % removal Sludge volume Pectin dose (mg/L) % r e m o v a l 0 5 10 15 20 25 30 S lu d g e v o lu m e ( m L /L ) 19 A CC EP TE D M A N U SC RI PT Figure 2 Effect of pectin dose on %removal and sludge volume 1 2 3.3. The effect of dye initial concentration on coagulation. The profile of the %removal 3 of Congo red dyes was observed in various initial concentrations of Congo red dyes (50–100 4 mg/L), with a fixed dose of alum (30 mg/L) and pectin (15 mg/L) at the best pH of 6. The result 5 is presented in Figure 3. 6 50 60 70 80 90 100 0 20 40 60 80 100 Alum Alum+pectin Pectin Alum Alum+pectin Pectin Congo red concentration (mg/L) % r e m o v a l 0 5 10 15 20 25 30 35 40 S lu d g e v o lu m e ( m L /L ) 7 Figure 3 Effect of initial dye concentration on %removal and sludge volume 8 9 At a dosage of 15 mg/L, pectin had a very poor coagulant activity and was unable to 10 coagulate the dye molecules. This is apparent from the %removal, which amounted to a mere 11 3.19% and fell as the initial dye concentration rose. Pectin typically has a negative high zeta 12 potential value at pH 6, which is around -25 mV [38]. In addition, Congo red has an isoelectric 13 point around pH 2 [39] that would be negatively charged as well at pH 6. Based on these facts, 14 it can be concluded that pectin does not act as the active coagulating agent in this study. 15 Furthermore, it can be observed that with the increase of Congo red concentration, the 16 %removal and sludge formation were also decreasing. This is possible due to the inadequacy 17 of active coagulating sites to neutralize the dye molecules with the increase of Congo red 18 concentration, as the interaction between coagulant and colloid has been reported as 19 A CC EP TE D M A N U SC RI PT stoichiometric interaction. The effect of pectin as coagulant-aid is discernible at the initial 1 Congo red concentration of 50–60 mg/L that gave %removal of 97.1 and 70.8% respectively. 2 This value increased significantly when compared to the one measured without using pectin 3 which gave 76.0 and 53.5% removals at the same initial Congo red concentration. This increase 4 confirmed a synergistic effect between alum and pectin that resulted in bigger observed flocs 5 (Figure 4) and higher Congo red removal. The possible interaction between Congo red, alum, 6 and pectin is illustrated in Figure 5. The negatively charged sulfonate groups in the Congo red 7 molecule would be neutralized by the positive Al3+, while the carboxylate groups in the pectin 8 structure could also interact with Al3+, resulting in a particle bridging effect (Figure 5.a). This 9 bridging mechanism could explain the formation of bigger flocs, as observed in Figure 5.b, 10 which resulted in a lower sludge volume and higher removal. Similar results of polysaccharides 11 that act as a bridge between smaller flocs have been reported previously [31][34][40]. 12 13 14 Figure 4. Observed flocs formation with 15 mg/L pectin (a) and without pectin (b) at pH 6. 15 [alum] = 30 mg/L. [Congo red] = 50 mg/L. 16 17 The results obtained in this study are compared with other coagulants for Congo red 18 removal, presented in Table 3. It can be observed that the coagulation performance of alum 19 with the aid of pectin could give a comparable coagulation performance with other coagulants 20 reported in the background literature. Furthermore, it can be seen that a smaller alum dosage 21 (30 mg/L) is needed to obtain a 97% removal with the 15 mg/L pectin addition, compared to 22 research conducted by [41] where 100 mg/L alum was required. 23 24 25 26 27 a. b. A CC EP TE D M A N U SC RI PT Table 3. Comparison of various coagulants for Congo red removal 28 Coagulant Coagulant-aid pH Congo red concentration (mg/L) % removal Reference Type Dosage (mg/L) Type Dosage (mg/L) Al2(SO4)3 30 Pectin 15 6 50 97.1 This study Al2(SO4)3 30 - - 6 50 76.0 This study CaCl2 4,000 Alginate 20 4 50 92.2 [42] FeCl3 160 Galactomannan 80 6 20 90.0 [15] FeCl3 10 A. tetragonus 300 3 500 92.0 [30] Polyaluminium chloride 15 - - 3 50 81.2 [40] Chitosan 25 - - 7 200 66.0 [43] Al2(SO4)3 nanoparticles 100 7 50 99.5 [41] 29 A CC EP TE D M A N U SC RI PT 30 Figure 5. Possible interaction between Al3+‒Congo red and Al3+‒pectin (a) and the particle 31 bridging of flocs by pectin (b) (Reused with permission from [40]; Copyright © Elsevier license 32 number 5524610093660) 33 34 4. CONCLUSION 35 36 In this study, low-methoxy pectin has been successfully utilized as a coagulant-aid in 37 Congo red dye removal. At various initial pHs, it was found that Congo red removal increases 38 from pH 3–6 with pH 6 as the best pH for coagulation via a charge neutralization mechanism. 39 The addition of pectin could assist the Congo red coagulation process. The addition of 15 mg/L 40 of pectin gave a 97% Congo red removal, compared to the 76% removal when only alum was 41 used as the coagulant. Overdosing of pectin could result in colloid re-stabilization that makes 42 a smaller floc formation and increases the sludge volume. At various initial Congo red 43 concentrations and fixed coagulant and coagulant-aid doses, the effect of pectin addition could 44 increase the Congo red removal at an initial concentration of 50–60 mg/L, which gave an 45 n O O H H H O OH H OH H O - O H H H H OH H O OH O O CH 3 NH2 S O O O - N N NH2 S O O O - N N Al 3+ Congo red pectin colloids alum small flocs pectin bigger flocs a. b. A CC EP TE D M A N U SC RI PT approximately 20% increase of removal compared to alum only. At a higher Congo red 46 concentration, the removal became lower than the one without pectin. This might happen due 47 to an inadequacy of alum at a fixed coagulant dosage with the increase of Congo red 48 concentration. This condition could lead to a competitive interaction of alum-Congo red and 49 alum-pectin, where both Congo red and pectin are negatively charged at the coagulation 50 condition. The results of this research study show that low-methoxy pectin is a potential 51 coagulant-aid that could work synergistically with alum in the coagulation process. Further 52 studies are required to observe the potential of the combination between alum and pectin in 53 other types of wastewaters, real wastewater, and optimization of the variables as well. 54 55 REFERENCES 56 57 [1] A. K. Verma, R. R. Dash, and P. Bhunia. (2012). "A review on chemical 58 coagulation/flocculation technologies for removal of colour from textile wastewaters". 59 Journal of Environmental Management. 93 : 154–168. 60 10.1016/j.jenvman.2011.09.012. 61 [2] G. Crini and E. Lichtfouse. (2019). "Advantages and disadvantages of techniques used 62 for wastewater treatment". Environmental Chemistry Letters. 17 : 145–155. 63 10.1007/s10311-018-0785-9. 64 [3] C.-Y. Yin. (2010). "Emerging usage of plant-based coagulants for water and 65 wastewater treatment". Process Biochemistry. 45 : 1437-1444. 66 10.1016/j.procbio.2010.05.030. 67 [4] H. Kristianto. (2021). "Recent advances on magnetic natural coagulant: a mini review". 68 Environmental Technology Review. 10 (1): 254-269. 69 10.1080/21622515.2021.1986576. 70 [5] A. Ibrahim, A. Z. Yaser, and J. Lamaming. (2021). "Synthesising tannin-based 71 coagulants for water and wastewater application: A review". Journal of Environmental 72 Chemical Engineering. 9 (1): 105007. 10.1016/j.jece.2020.105007. 73 [6] E. Díaz-Montes. (2022). "Polysaccharides: Sources, Characteristics, Properties, and 74 Their Application in Biodegradable Films". Polysaccharides. 3 : 480-501. 75 10.3390/polysaccharides3030029. 76 A CC EP TE D M A N U SC RI PT https://doi.org/10.1016/j.jenvman.2011.09.012 https://doi.org/10.1007/s10311-018-0785-9 https://doi.org/10.1016/j.procbio.2010.05.030 https://doi.org/10.1080/21622515.2021.1986576 https://doi.org/10.1016/j.jece.2020.105007 https://doi.org/10.3390/polysaccharides3030029 [7] C. Y. Teh, T. Y. Wu, and J. C. Juan. (2014). "Optimization of agro-industrial 77 wastewater treatment using unmodified rice starch as a natural coagulant". Industrial 78 Crops and Products. 56 : 17–26. 10.1016/j.indcrop.2014.02.018. 79 [8] M. S. Zafar, M. Tausif, M. Mohsin, S. W. Ahmad, and M. Zia-ul-Haq. (2015). "Potato 80 Starch as a Coagulant for Dye Removal from Textile Wastewater". Water, Air, & Soil 81 Pollution. 226 (8): 244. 10.1007/s11270-015-2499-y. 82 [9] H. A. Aziz and N. I. M. Sobri. (2015). "Extraction and application of starch-based 83 coagulants from sago trunk for semi-aerobic landfill leachate treatment". 84 Environmental Science and Pollution Research. 22 : 16943–16950. 10.1007/s11356-85 015-4895-7. 86 [10] S. Y. Choy, K. N. Prasad, T. Y. Wu, M. E. Raghunandan, and R. N. Ramanan. (2016). 87 "Performance of conventional starches as natural coagulants forturbidity removal". 88 Ecological Engneering. 94 : 352-364. 10.1016/j.ecoleng.2016.05.082. 89 [11] H. Kristianto, A. Jennifer, A. K. Sugih, and S. Prasetyo. (2020). "Potensi Polisakarida 90 dari Limbah Buah-buahan sebagai Koagulan Alami dalam Pengolahan Air dan Limbah 91 Cair: Review". Jurnal Rekayasa Proses. 14 (2): 108-127. 10.22146/jrekpros.57798. 92 [12] R. Sanghi, B. Bhatttacharya, and V. Singh. (2002). "Cassia angustifolia seed gum as an 93 effective natural coagulant for decolourisation of dye solutions". Green Chemistry. 4 : 94 252–254. 10.1039/B200067A. 95 [13] R. Sanghi, B. Bhattacharya, A. Dixit, and V. Singh. (2006). "Ipomorea dasysperma 96 seed gum: An effective natural coagulant for the decolorization of textile dye 97 solutions". Journal of Environmental Management. 81 (1): 36-41. 98 10.1016/j.jenvman.2005.09.015. 99 [14] K. P. Y. Shak and T. Y. Wu. (2015). "Optimized use of alum together with unmodified 100 Cassia obtusifolia seed gum as a coagulant aid in treatment of palm oil mill effluent 101 under natural pH of wastewater". Industrial Crops and Products. 76 : 1169–1178. 102 10.1016/j.indcrop.2015.07.072. 103 [15] H. Kristianto, S. A. Saraswati, S. Prasetyo, and A. K. Sugih. (2023). "The utilization of 104 galactomannan from spent coffee grounds as a coagulant aid for treatment of synthetic 105 Congo red wastewater". Environmental Development and Sustainability. 25 : 5443–106 5457. 10.1007/s10668-022-02274-x. 107 [16] K. Q. Lau, M. R. Sabran, and S. R. Shafie. (2021). "Utilization of Vegetable and Fruit 108 By-products as Functional Ingredient and Food". Frontiers in Nutrition. 8 : 661693. 109 10.3389/fnut.2021.661693. 110 A CC EP TE D M A N U SC RI PT https://doi.org/10.1016/j.indcrop.2014.02.018 https://doi.org/10.1007/s11270-015-2499-y https://doi.org/10.1007/s11356-015-4895-7 https://doi.org/10.1007/s11356-015-4895-7 https://doi.org/10.1016/j.ecoleng.2016.05.082 https://doi.org/10.22146/jrekpros.57798 https://doi.org/10.1039/B200067A https://doi.org/10.1016/j.jenvman.2005.09.015 https://doi.org/10.1016/j.indcrop.2015.07.072 https://doi.org/10.1007/s10668-022-02274-x https://doi.org/10.3389/fnut.2021.661693 [17] S. Y. Choy, K. M. N. Prasad, T. Y. Wu, M. E. Raghunandan, B. Yang, S.-M. Phang, 111 and R. N. Ramanan. (2017). "Isolation, characterization and the potential use of starch 112 from jackfruit seed wastes as a coagulant aid for treatment of turbid water". 113 Environmental Science and Pollution Research. 24 : 2876–2889. 10.1007/s11356-016-114 8024-z. 115 [18] M. V. Nsom, E. P. Etape, J. F. Tendo, B. V. Namond, P. T. Chongwain, M. D. Yufanyi, 116 and N. William. (2019). "A Green and Facile Approach for Synthesis of Starch-Pectin 117 Magnetite Nanoparticles and Application by Removal of Methylene Blue from Textile 118 Effluent". Journal of Nanomaterials. 2019 : 4576135. 10.1155/2019/4576135. 119 [19] M. C. N. Picot-Allain, B. Ramasawmy, and M. N. Emmambux. (2022). "Extraction, 120 Characterisation, and Application of Pectin from Tropical and Sub-Tropical Fruits: A 121 Review". Food Reviews International. 38 (3): 10.1080/87559129.2020.1733008. 122 [20] M. Moslemi. (2021). "Reviewing the recent advances in application of pectin for 123 technical and health promotion purposes: From laboratory to market". Carbohydrate 124 Polymers. 254 : 117324. 10.1016/j.carbpol.2020.117324. 125 [21] F. Naqash, F. A. Masoodi, S. A. Rather, S. M. Wani, and A. Gani. (2017). "Emerging 126 concepts in the nutraceutical and functional properties of pectin—A Review". 127 Carbohydrate Polymers. 168 : 227-239. 10.1016/j.carbpol.2017.03.058. 128 [22] H. A. Schols and A. G. J. Voragen. (1996). "Complex pectins:structure elucidation 129 using enzymes". Progress in Biotechnology. 14 : 3–19. 10.1016/S0921-130 0423(96)80242-5. 131 [23] B. M. Yapo and D. Gnakri. (2014). In "K. G. Ramawat and J.-M. Mérillon (Eds) 132 Polysaccharides: Bioactivity and Biotechnology". Springer, Cham. 1729-1749. 133 10.1007/978-3-319-16298-0_62. 134 [24] M. Lapointe and B. Barbeau. (2020). "Understanding the roles and characterizing the 135 intrinsic properties of synthetic vs. natural polymers to improve clarification through 136 interparticle Bridging: A review". Separation and Purification Technology. 231 : 137 115893. 10.1016/j.seppur.2019.115893. 138 [25] S. J. C. d. Rosemond and K. Liber. (2009). "Wastewater treatment polymers identified 139 as the toxic component of a diamond mine effluent". Environmental Toxicology and 140 Chemistry. 23 (9): 2234-2242. 10.1897/03-609. 141 [26] D. Ibarra-Rodríguez, J. Lizardi-Mendoza, E. A. López-Maldonado, and M. T. Oropeza-142 Guzmán. (2017). "Capacity of ‘nopal’ pectin as a dual coagulant-flocculant agent for 143 A CC EP TE D M A N U SC RI PT https://doi.org/10.1007/s11356-016-8024-z https://doi.org/10.1007/s11356-016-8024-z https://doi.org/10.1155/2019/4576135 https://doi.org/10.1080/87559129.2020.1733008 https://doi.org/10.1016/j.carbpol.2020.117324 https://doi.org/10.1016/j.carbpol.2017.03.058 https://doi.org/10.1016/S0921-0423(96)80242-5 https://doi.org/10.1016/S0921-0423(96)80242-5 https://doi.org/10.1007/978-3-319-16298-0_62 https://doi.org/10.1016/j.seppur.2019.115893 https://doi.org/https:/doi.org/10.1897/03-609 heavy metals removal". Chemical Engineering Journal. 323 : 19-28. 144 10.1016/j.cej.2017.04.087. 145 [27] M. Kebaili, S. Djellali, M. Radjai, N. Drouiche, and H. Lounici. (2018). "Valorization 146 of orange industry residues to form a natural coagulant and adsorbent". Journal of 147 Industrial and Engineering Chemistry. 64 : 292-299. 10.1016/j.jiec.2018.03.027. 148 [28] F. Shao, J. Xu, J. Zhang, L. Wei, C. Zhao, X. Cheng, C. Lu, and Y. Fu. (2021). "Study 149 on the influencing factors of natural pectin's flocculation: Their sources, modification, 150 and optimization". Water Environment Research. 93 (10): 2261-2273. 151 10.1002/wer.1598. 152 [29] A. A. Cerqueira and M. R. d. C. Marques. (2012). In: " J. S. Gomes (Ed) New 153 Technologies in the Oil and Gas Industry". IntechOpen. 154 [30] M. Chethana, L. G. Sorokhaibam, V. M. Bhandari, S. Raja, and V. V. Ranade. (2016). 155 "Green approach to Dye Wastewater Treatment using Biocoagulants". ACS Sustainable 156 Chemistry and Engineering. 4 (5): 2495–2507. 10.1021/acssuschemeng.5b01553. 157 [31] S. Zhao, B. Gao, Q. Yue, Y. Wang, Q. Li, H. Dong, and H. Yan. (2014). "Study of 158 Enteromorpha polysaccharides as a new-style coagulant aid in dye wastewater 159 treatment". Carbohydrate Polymers. 103 : 179-186. 10.1016/j.carbpol.2013.12.045. 160 [32] M. H. Zonoozi, M. R. A. Moghaddam, and M. Arami. (2009). 161 "Coagulation/flocculation of dye-containing solutions using polyaluminium chloride 162 and alum". Water Science & Technology. 59 : 1343-1351. 10.2166/wst.2009.128. 163 [33] S.-S. Liu and T.-T. Liang. (2004). "Return sludge employed in enhancement of color 164 removal in the integrally industrial wastewater treatment plant". Water Research. 38 165 (1): 103-110. 10.1016/j.watres.2003.09.006. 166 [34] S.-C. Chua, F.-K. Chong, M. A. Malek, M. R. U. Mustafa, N. Ismail, W. Sujarwo, J.-167 W. Lim, and Y.-C. Ho. (2020). "Optimized Use of Ferric Chloride and Sesbania Seed 168 Gum (SSG) as Sustainable Coagulant Aid for Turbidity Reduction in Drinking Water 169 Treatment". Sustainability. 12 (6): 2273. 10.3390/su12062273. 170 [35] N. A. Awang and H. A. Aziz. (2012). "Hibiscus rosa-sinensis leaf extract as coagulant 171 aid in leachate treatment". Applied Water Science. 2 : 293–298. 10.1007/s13201-012-172 0049-y. 173 [36] P. W. Wong, T. T. Teng, and N. A. R. N. Norulaini. (2007). "Efficiency of the 174 Coagulation-Flocculation Method for the Treatment of Dye Mixtures Containing 175 Disperse and Reactive Dye". Water Quality Research Journal. 42 (1): 54-62. 176 10.2166/wqrj.2007.008. 177 A CC EP TE D M A N U SC RI PT https://doi.org/10.1016/j.cej.2017.04.087 https://doi.org/10.1016/j.jiec.2018.03.027 https://doi.org/10.1002/wer.1598 https://doi.org/10.1021/acssuschemeng.5b01553 https://doi.org/10.1016/j.carbpol.2013.12.045 https://doi.org/10.2166/wst.2009.128 https://doi.org/10.1016/j.watres.2003.09.006 https://doi.org/10.3390/su12062273 https://doi.org/10.1007/s13201-012-0049-y https://doi.org/10.1007/s13201-012-0049-y https://doi.org/10.2166/wqrj.2007.008 [37] Y. A. J. Al-Hamadani, M. S. Yusoff, M. Umar, M. J. K. Bashir, and M. N. Adlan. 178 (2011). "Application of psyllium husk as coagulant and coagulant aid in semi-aerobic 179 landfill leachate treatment". Journal of Hazardous Materials. 190 (1-3): 582-587. 180 10.1016/j.jhazmat.2011.03.087. 181 [38] V. B. V. Maciel, C. M. P. Yoshida, S. M. S. S. Pereira, F. M. Goycoolea, and T. T. 182 Franco. (2017). "Electrostatic Self-Assembled Chitosan-Pectin Nano- and 183 Microparticles for Insulin Delivery". Molecules. 22 (10): 1707. 184 10.3390/molecules22101707. 185 [39] J. Kristanda, K. Sandrosa, H. Kristianto, S. Prasetyo, and A. K. Sugih. (2021). 186 "Optimization study of Leucaena leucocephala seeds extract as natural coagulant on 187 decolorization of aqueous Congo red solutions". Arabian Journal for Science and 188 Engineering. 46 (7): 6275-6286. 10.1007/s13369-020-05008-1. 189 [40] M. M. Sudirgo, R. A. Surya, H. Kristianto, S. Prasetyo, and A. K. Sugih. (2023). 190 "Application of xanthan gum as coagulant-aid for decolorization of synthetic Congo 191 red wastewater". Heliyon 9 (4): E15011. 10.1016/j.heliyon.2023.e15011. 192 [41] J. Garvasis, A. R. Prasad, K. O. Shamsheera, P. K. Jaseela, and A. Joseph. (2020). 193 "Efficient removal of Congo red from aqueous solutions using phytogenic aluminum 194 sulfate nano coagulant". Materials Chemistry and Physics. 251 : 123040. 195 10.1016/j.matchemphys.2020.123040. 196 [42] G. Vijayaraghavan and S. Shanthakumar. (2016). "Performance study on algal alginate 197 as natural coagulant for the removal of Congo red dye". Desalination and Water 198 Treatment. 57 : 6384–6392. 10.1080/19443994.2015.1008578. 199 [43] H. Patel and R. T. Vashi. (2012). "Removal of Congo Red dye from its aqueous solution 200 using natural coagulants". Journal of Saudi Chemical Society. 16 : 131–136. 201 10.1016/j.jscs.2010.12.003. 202 203 A CC EP TE D M A N U SC RI PT https://doi.org/10.1016/j.jhazmat.2011.03.087 https://doi.org/10.3390/molecules22101707 https://doi.org/10.1007/s13369-020-05008-1 https://doi.org/10.1016/j.heliyon.2023.e15011 https://doi.org/10.1016/j.matchemphys.2020.123040 https://doi.org/10.1080/19443994.2015.1008578 https://doi.org/10.1016/j.jscs.2010.12.003