This study investigates the properties and potential application of Mg-PKS biochar composite for methylene blue solution (MB) adsorption. The Mg-PKS biochar composite was developed from palm kernel shell biochar via steam activation followed by MgSO4 treatment and carbonization. The effect of process parameters such as solution pH (4-10), contact time (30-90 min) and adsorbent dosage (0.1-0.5 g) were investigated via central composite design, response surface methodology. Results revealed that the Mg-PKS biochar composite has irregular shapes pore structure from SEM analysis, a surface area of 674 m2g-1 and average pore diameters of 7.2195 μm based on BET analysis. RSM results showed that the optimum adsorption of MB onto Mg-biochar composite was at pH 10, 30 min contact time and 0.5 g/100 mL dosage with a removal efficiency of 98.50%. In conclusion, Mg treatment is a potential alternative to other expensive chemical treatment methods for biochar upgrading to the adsorbent.

• Albadarin, A. B., Collins, M. N., Naushad, M., Shirazian, S., & Mangwandi, C. (2016). Activated lignin chitosan extruded blends for efficient adsorption of methylene blue. Chemical Engineering Journal, 307, 264-272. https://doi.org/10.1016/j.cej.2016.08.089

• Alene, A. N., Abate, G. Y., & Habte, A. T. (2020). Bioadsorption of basic blue dye from aqueous solution onto raw and modified waste ash as economical alternative bioadsorbent. Journal of Chemistry, 2020, Article 8746035. https://doi.org/10.1155/2020/8746035

• Allouss, D., Essamlali, Y., Amadine, O., Chakir, A., & Zahouily, M. (2019). Response surface methodology for optimization of methylene blue adsorption onto carboxymethyl. RSC Advances, 9, 37858-37869. https://doi.org/10.1039/c9ra06450h

• Antunes, E., Jacob, M. V, Brodie, G., & Schneider, P. A. (2017). Silver removal from aqueous solution by biochar produced from biosolids via microwave pyrolysis. Journal of Environmental Management, 203, 264-272. https://doi.org/10.1016/j.jenvman.2017.07.071

• Ba, O. S., Ka, H., Shoe, T., Ya, H., & Yo, N. (2020). Novel approach for effective removal of methylene blue dye from water using fava bean peel waste. Scientific Reports, 10, 1-10. https://doi.org/10.1038/s41598-020-64727-5

• Bendaho, D., Driss, T. A., & Bassou, D. (2015). Removal of cationic dye methylene blue from aqueous solution by adsorption on Algerian clay. International Journal of Waste Resources, 5(1), 1-6. https://doi.org/10.4303/2252-5211.1000175

• Carvalho Eufrásio Pinto, M., David Da Silva, D., Amorim Gomes, A. L., Menezes Dos Santos, R. M., Alves De Couto, R. A., Ferreira De Novais, R., Leopoldo Constantino, V. R., Tronto, J., & Pinto, F. G. (2019). Biochar from carrot residues chemically modified with magnesium for removing phosphorus from aqueous solution. Journal of Cleaner Production, 222, 36-46. https://doi.org/10.1016/j.jclepro.2019.03.012

• Choi, Y., Gurav, R., Kim, H. J., Yang, Y., & Bhatia, S. K. (2020). Evaluation for simultaneous removal of anionic and cationic dyes onto maple leaf-derived biochar using response surface methodology. Applied Sciences, 10(9), Article 2982. https://doi.org/10.3390/app10092982

• Fan, S., Tang, J., Wang, Y., Li, H., Zhang, H., Tang, J., Wang, Z., & Li, X. (2016). Biochar prepared from co-pyrolysis of municipal sewage sludge and tea waste for the adsorption of methylene blue from aqueous solutions: Kinetics, isotherm, thermodynamic and mechanism. Journal of Molecular Liquids, 220, 432-441. https://doi.org/10.1016/j.molliq.2016.04.107

• Fang, C., Zhang, T., Li, P., Jiang, R. F., & Wang, Y. C. (2014). Application of magnesium modified corn biochar for phosphorus removal and recovery from swine wastewater. International Journal of Environmental Research and Public Health, 11(9), 9217-9237. https://doi.org/10.3390/ijerph110909217

• Fatiha, M., & Belkacem, B. (2015). Adsorption of methylene blue from aqueous solutions using natural clay. Journal of Materials and Environmental Science, 3(5), 1-7. https://doi.org/10.4172/2157-7587.1000143

• García, J. R., Sedran, U., Zaini, M. A. A., & Zakaria, Z. A. (2018). Preparation, characterization, and dye removal study of activated carbon prepared from palm kernel shell. Environmental Science and Pollution Research, 25(6), 5076-5085. https://doi.org/10.1007/s11356-017-8975-8

• Gnanasundaram, N., Loganathan, M., & Singh, A. (2017). Optimization and performance parameters for adsorption of Cr6+ by microwave assisted carbon from Sterculia foetida shells. IOP Conference Series: Materials Science and Engineering, 206(1), 1-10. https://doi.org/10.1088/1757-899X/206/1/012065

• Guarín, J. R., Moreno-Pirajan, J. C., & Giraldo, L. (2018). Kinetic study of the bioadsorption of methylene blue on the surface of the biomass obtained from the Algae D. antarctica. Journal of Chemistry, 2018, Article 2124845. https://doi.org/10.1155/2018/2124845

• Hasbullah, T. N. A. T., Selaman, O. S., & Rosli, N. A. (2014). Removal of dye from aqeuous solutions using chemical activated carbon prepared from jackfruit (Artocarpus heterophyllus) peel waste. UNIMAS E-Journal of Civil Engineering, 5(1), 34-38.

• He, R., Peng, Z., Lyu, H., Huang, H., Nan, Q., & Tang, J. (2018). Synthesis and characterization of an iron-impregnated biochar for aqueous arsenic removal. Science of the Total Environment, 612, 1177-1186. https://doi.org/10.1016/j.scitotenv.2017.09.016

• Jawad, A. H., Rashid, R. A., Ishak, M. A. M., & Wilson, L. D. (2016). Adsorption of methylene blue onto activated carbon developed from biomass waste by H2SO4 activation: Kinetic, equilibrium and thermodynamic studies. Desalination and Water Treatment, 57(52), 25194-25206. https://doi.org/10.1080/19443994.2016.1144534

• Jellali, S., Diamantopoulos, E., Haddad, K., Anane, M., Durner, W., & Mlayah, A. (2016). Lead removal from aqueous solutions by raw sawdust and magnesium pretreated biochar : Experimental investigations and numerical modelling. Journal of Environmental Management, 180, 439-449. https://doi.org/10.1016/j.jenvman.2016.05.055

• Jindo, K., Mizumoto, H., Sawada, Y., Sanchez-Monedero, M. A., & Sonoki, T. (2014). Physical and chemical characterization of biochars derived from different agricultural residues. Biogeosciences, 11(23), 6613-6621. https://doi.org/10.5194/bg-11-6613-2014

• Johari, K., Saman, N., Tien, S. S., Siew Chin, C., Kong, H., & Mat, H. (2016). Removal of elemental mercury by coconut pith char adsorbents. Procedia Engineering, 148, 1357-1362. https://doi.org/10.1016/j.proeng.2016.06.588

• Jung, K., & Ahn, K. (2015). Fabrication of porosity-enhanced MgO/biochar for removal of phosphate from aqueous solution : Application of a novel combined electrochemical modification method. Bioresource Technology, 200, 1029-1032. https://doi.org/10.1016/j.biortech.2015.10.008

• Karaer, H., & Kaya, I. (2016). Synthesis, characterization of magnetic chitosan/active charcoal composite and using at the adsorption of methylene blue and reactive blue. Microporous and Mesoporous Materials, 232, 26-38. https://doi.org/10.1016/j.micromeso.2016.06.006

• Kim, H. (2014). Analysis of variance (ANOVA) comparing means of more than two groups. Restorative Dentistry and Endodontics, 7658, 74-77. https://doi.org/10.5395/rde.2014.39.1.74

• Komnitsas, K. A., & Zaharaki, D. (2016). Morphology of modified biochar and its potential for phenol removal from aqueous solutions. Frontiers in Environmental Science, 4(April), 1-11. https://doi.org/10.3389/fenvs.2016.00026

• Kuang, Y., Zhang, X., & Zhou, S. (2020). Adsorption of methylene blue in water onto activated carbon by surfactant modification. Water, 12, 1-19. https://doi.org/10.3390/w12020587

• Lam, S. S., Liew, R. K., Cheng, C. K., Rasit, N., Ooi, C. K., Ma, N. L., Ng, J. H., Lam, W. H., Chong, C. T., & Chase, H. A. (2018). Pyrolysis production of fruit peel biochar for potential use in treatment of palm oil mill effluent. Journal of Environmental Management, 213, 400-408. https://doi.org/10.1016/j.jenvman.2018.02.092

• Liao, P., Zhan, Z., Dai, J., Wu, X., Zhang, W., Wang, K., & Yuan, S. (2013). Adsorption of tetracycline and chloramphenicol in aqueous solutions by bamboo charcoal: A batch and fixed-bed column study. Chemical Engineering Journal, 228, 496-505. https://doi.org/10.1016/j.cej.2013.04.118

• Liew, R. K., Nam, W. L., Chong, M. Y., Phang, X. Y., Su, M. H., Yek, P. N. Y., Ma, N. L., Cheng, C. K., Chong, C. T., & Lam, S. S. (2017). Oil palm waste: An abundant and promising feedstock for microwave pyrolysis conversion into good quality biochar with potential multi-applications. Process Safety and Environmental Protection, 115, 57-69. https://doi.org/10.1016/j.psep.2017.10.005

• Liu, W. J., Jiang, H., & Yu, H. Q. (2015). Development of biochar-Based functional materials: toward a sustainable platform carbon material. Chemical Reviews, 115(22), 12251-12285. https://doi.org/10.1021/acs.chemrev.5b00195

• Liu, Z., & Han, G. (2015). Production of solid fuel biochar from waste biomass by low temperature pyrolysis. Fuel, 158, 159-165. https://doi.org/10.1016/j.fuel.2015.05.032

• Mahmood, W. M. F. W., Ariffin, M. A., Harun, Z., Ghani, J. A., Ishak, N. A. I. M., & Rahman, M. N. A. (2015). Characterisation and potential use of biochar from gasified oil palm wastes. Journal of Engineering Science and Technology, 10(2014), 45-54. https://www.researchgate.net/publication/287534129_Characterisation_and_potential_use_of_biochar_from_gasified_oil_palm_wastes

• Mahmoudi, K., Hamdi, N., & Srasra, E. (2015). Study of adsorption of methylene blue onto activated carbon from lignite. Surface Engineering and Applied Electrochemistry, 51(5), 427-433. https://doi.org/10.3103/S1068375515050105

• Marrakchi, F., Ahmed, M. J., Khanday, W. A., Asif, M., & Hameed, B. H. (2017). Mesoporous-activated carbon prepared from chitosan flakes via single-step sodium hydroxide activation for the adsorption of methylene blue. International Journal of Biological Macromolecules, 98, 233-239. https://doi.org/10.1016/j.ijbiomac.2017.01.119

• Mousavi, S. A., Mehralian, M., Khashij, M., & Parvaneh, S. (2017). Methylene blue removal from aqueous solutions by activated carbon prepared from N. Microphyllum (AC-NM): RSM analysis, isotherms and kinetic studies. Global Nest Journal, 19(4), 697-705.

• Niran, O. B., Olawale, S. A., & Ushie, U. J. (2018). Isotherm studies of adsorption of methylene blue by palm kernel shell. Asian Journal of Applied Chemistry Research, 1(1), 1-9. https://doi.org/10.9734/AJACR/2018/41300

• Ocholi, O. J., Gimba, C. E., Ndukwe, G. I., Turoti, M., Abechi, S. E., & Edogbanya, P. R. O. (2016). Effect of time on the adsorption of methylene blue , methyl orange and indigo carmine onto activated carbon. IOSR Journal of Applied Chemistry, 9(9), 55-62. https://doi.org/10.9790/5736-0909015562

• Ozturk, D., & Sahan, T. (2015). Design and optimization of Cu ( II ) adsorption conditions from aqueous solutions by low-cost adsorbent pumice with response surface methodology. Polish Journal of Environmental Studies, 24(4), 1749-1756. https://doi.org/10.15244/pjoes/40270

• Pandimurugan, R., & Thambidurai, S. (2016). Synthesis of seaweed-ZnO-PANI hybrid composite for adsorption of methylene blue dye. Biochemical Pharmacology, 4(1), 1332-1347. https://doi.org/10.1016/j.jece.2016.01.030

• Pang, J., Fu, F., Ding, Z., Lu, J., Li, N., & Tang, B. (2017). Adsorption behaviors of methylene blue from aqueous solution on mesoporous birnessite. Journal of the Taiwan Institute of Chemical Engineers, 77, 168-176. https://doi.org/10.1016/j.jtice.2017.04.041

• Patel, B., & Gami, B. (2012). Biomass characterization and its use as solid fuel for combustion. Iranica Journal of Energy & Environment, 3(2), 123-128. https://doi.org/10.5829/idosi.ijee.2012.03.02.0071

• Pathania, D., Sharma, S., & Singh, P. (2017). Removal of methylene blue by adsorption onto activated carbon developed from Ficus carica bast. Arabian Journal of Chemistry, 10, 1445-1451. https://doi.org/10.1016/j.arabjc.2013.04.021

• Pinto, M. D. C. E., da Silva, D. D., Gomes, A. L. A., dos Santos, R. M. M., de Couto, R. A. A., de Novais, R. F., Constantino, V. R. L., Tronto, J., & Pinto, F. G. (2019). Biochar from carrot residues chemically modified with magnesium for removing phosphorus from aqueous solution. Journal of Cleaner Production, 222, 36-46. https://doi.org/10.1016/j.jclepro.2019.03.012

• Rajapaksha, A. U., Chen, S. S., Tsang, D. C. W., Zhang, M., Vithanage, M., Mandal, S., Gao, B., Bolan, N. S., & Ok, Y. S. (2016). Engineered/designer biochar for contaminant removal/immobilization from soil and water: Potential and implication of biochar modification. Chemosphere, 148(October), 276-291. https://doi.org/10.1016/j.chemosphere.2016.01.043

• Riddle, M., Bergström, L., Schmieder, F., Lundberg, D., Condron, L., & Cederlund, H. (2019). Impact of biochar coated with magnesium (hydr)oxide on phosphorus leaching from organic and mineral soils. Journal of Soils and Sediments, 19(4), 1875-1889. https://doi.org/10.1007/s11368-018-2197-7

• Rout, T., Pradhan, D., Singh, R. K., & Kumari, N. (2016). Exhaustive study of products obtained from coconut shell pyrolysis. Journal of Environmental Chemical Engineering, 4(3), 3696-3705. https://doi.org/10.1016/j.jece.2016.02.024

• Rugayah, A. F., Astimar, A. A., & Norzita, N. (2014). Preparation and characterisation of activated carbon from palm kernel shell by physical activation with steam. Journal of Oil Palm Research, 26(3), 251-264.

• Sahu, S., Pahi, S., Tripathy, S., Singh, S. K., Behera, A., Sahu, U. K., & Patel, R. K. (2020). Adsorption of methylene blue on chemically modified lychee seed biochar: dynamic, equilibrium, and thermodynamic study. Journal of Molecular Liquids, 315, Article 113743. https://doi.org/10.1016/j.molliq.2020.113743

• Sarkar, D. (2015). Fuels and combustion. In Thermal power plant (pp. 91-137). Elsevier. https://doi.org/10.1016/B978-0-12-801575-9.00003-2

• Sartape, A., Mandhare, A., Salvi, P., Pawar, D., Raut, P., Anuse, M., & Kolekar, S. (2012). Removal of Bi (III) with adsorption technique using coconut shell activated carbon. Chinese Journal of Chemical Engineering, 20(4), 768-775. https://doi.org/10.1016/S1004-9541(11)60247-4

• Shen, Z., Zhang, J., Hou, D., Tsang, D. C. W., Ok, Y. S., & Alessi, D. S. (2018). Synthesis of MgO-coated corncob biochar and its application in lead stabilization in a soil washing residue. Environment International, 122, 357-362. https://doi.org/10.1016/j.envint.2018.11.045

• Sizmur, T., Fresno, T., Akgül, G., Frost, H., & Moreno, E. (2017). Biochar modification to enhance sorption of inorganics from water. Bioresource Technology, 246, 34-47. https://doi.org/10.1016/j.biortech.2017.07.082

• Stat-Ease. (2021). Response surface. Retrieved December 03, 2019, from https://www.statease.com/docs/v11/tutorials/multifactor-rsm/

• Tan, X., Liu, Y., Zeng, G., Wang, X., Hu, X., Gu, Y., & Yang, Z. (2015). Application of biochar for the removal of pollutants from aqueous solutions. Chemosphere, 125, 70-85. https://doi.org/10.1016/j.chemosphere.2014.12.058

• Tang, R., Dai, C., Li, C., Liu, W., Gao, S., & Wang, C. (2017). Removal of methylene blue from aqueous solution using agricultural residue walnut shell: Equilibrium, kinetic, and thermodynamic studies. Journal of Chemistry, 2017, 1-10. https://doi.org/10.1155/2017/8404965

• Thakkar, A., & Saraf, M. (2014). Application of statistically based experimental designs to optimize cellulase production and identification of gene. Natural Products and Bioprospecting, 4, 341-351. https://doi.org/10.1007/s13659-014-0046-y

• Tripathi, M., Sahu, J. N., & Ganesan, P. (2016). Effect of process parameters on production of biochar from biomass waste through pyrolysis: A review. Renewable and Sustainable Energy Reviews, 55, 467-481. https://doi.org/10.1016/j.rser.2015.10.122

• Wahi, R., Aziz, S. M. A., Hamdan, S., & Ngaini, Z. (2015). Biochar production from agricultural wastes via low-temperature microwave carbonization. In 2015 IEEE international RF and microwave conference (RFM) (pp. 244-247). IEEE Conference Publication. https://doi.org/10.1109/RFM.2015.7587754

• Wahi, R., Chuah, L. A., Ngaini, Z., Nourouzi, M. M., & Choong, T. S. Y. (2014). Esterification of M. sagu bark as an adsorbent for removal of emulsified oil. Journal of Environmental Chemical Engineering, 2(1), 324-331. https://doi.org/10.1016/j.jece.2013.12.010

• Wu, Z., Zhong, H., Yuan, X., Wang, H., Wang, L., Chen, X., Zeng, G., & Wu, Y. (2014). Adsorptive removal of methylene blue by rhamnolipid-functionalized graphene oxide from wastewater. Water Research, 67, 330-344. https://doi.org/10.1016/j.watres.2014.09.026

• Xue-jiao, C., Qi-mei, L. I. N., Rizwan, M., Xiao-rong, Z., & Gui-tong, L. I. (2019). Steam explosion of crop straws improves the characteristics of biochar as a soil amendment. Journal of Integrative Agriculture, 18(7), 1486-1495. https://doi.org/10.1016/S2095-3119(19)62573-6

• Zhang, M., Gao, B., Yao, Y., Xue, Y., & Inyang, M. (2012). Synthesis of porous MgO-biochar nanocomposites for removal of phosphate and nitrate from aqueous solutions. Chemical Engineering Journal, 210, 26-32. https://doi.org/10.1016/j.cej.2012.08.052

• Zhao, X., Yi, S., Dong, S., Xu, H., Sun, Y., & Hu, X. (2018). Removal of Levofloxacin from aqueous solution by Magnesium-impregnated Biochar: Batch and column experiments. Chemical Speciation and Bioavailability, 30(1), 68-75. https://doi.org/10.1080/09542299.2018.1487775

• Zhou, R., Zhang, M., Zhou, J., & Wang, J. (2019). Optimization of biochar preparation from the stem of Eichhornia crassipes using response surface methodology on adsorption of Cd2+. Scientific Reports, 9, 1-17. https://doi.org/10.1038/s41598-019-54105-1

• Zhu, S., Fang, S., Huo, M., Yu, Y., Chen, Y., Yang, X., & Geng, Z. (2015). A novel conversion of the groundwater treatment sludge to magnetic particles for the adsorption of methylene blue. Journal of Hazardous Materials, 292, 173-179. https://doi.org/10.1016/j.jhazmat.2015.03.028