Removal of Pb(II) from Aqueous Solutions Using Magnetic Mesoporous Silica Nanocomposites: Modeling and Optimization Based on Response Surface Methodology

Document Type : Research Paper


1 PhD. Student, Dept. of Chemistry, Mashhad Branch, Islamic Azad University, Mashhad, Iran

2 Assoc. Prof., Dept. of Chemistry, Mashhad Branch, Islamic Azad University, Mashhad, Iran

3 Assoc. Prof., Dept. of Chemistry, Neyshabur Branch, Islamic Azad University, Neyshabur, Iran and Advanced Research Center of Chemistry Biochemistry & Nanomaterial, Neyshabur Branch, Islamic Azad University, Neyshabur, Iran


In the adsorption process of heavy metals, a major challenge is to design and develop adsorbent materials in an abundance of accessible adsorption sites with high affinity to achieve both fast adsorption kinetics and increased adsorption capacity for toxic contaminants. The removal of pollutants by mesoporous silica adsorbents is now in the limelight due to the nontoxicity and biocompatibility of these materials with the environment. In this study, a fibrous core-shell magnetic mesoporous composite (Fe3O4/SiO2/KCC-1) was successfully synthesized and used as a nano-adsorbent to remove Pb(II) from an aqueous solution. The adsorbent was characterized by employing TEM, SEM, FTIR, VSM, XRD, and N2 adsorption–desorption techniques. According to the results, Fe3O4/SiO2/KCC-1 was successfully synthesized with an average pore diameter of 7.94 nm, a surface area of 813.07 m2 g-1, and a pore volume of 1.41 cm3 g-1. The response surface methodology (RSM) was then adopted in the central composite design (CCD) to optimize parameters of the adsorption process. The optimal conditions for Pb(II) adsorption were then determined at a temperature of 80 °C, an adsorption dosage of 0.04 g L-1, a pH 5.6, and the contact time of 38 min. The removal rate of Pb(II) was 90%. Studies of equilibrium and kinetics indicated that the adsorption process followed Langmuir’s isotherm and the pseudo-first-order model with correlation coefficients of 0.98 and 0.99, respectively. The maximum adsorption capacity of Fe3O4/SiO2/KCC-1 was reported 574.4 mg g-1. Moreover, the thermodynamic parameters known as enthalpy (ΔH° = +5.84 kJ mol-1), negative Gibbs free energy (∆G°) values, and entropy (ΔS° = +23.42 kJ mol-1 K-1) indicated that the adsorption was endothermic and spontaneous with the increased disorder at the solid–liquid interphase.


Abd Ali, L. I., Ibrahim, W. A. W., Sulaiman, A., Kamboh, M. A. & Sanagi, M. M. 2016. New chrysin-functionalized silica-core shell magnetic nanoparticles for the magnetic solid phase extraction of copper ions from water samples. Talanta, 148, 191-199.
Ahmad, S. Z. N., Salleh, W. N. W., Ismail, A. F., Yusof, N., Yusop, M. Z. M. & Aziz, F. 2020. Adsorptive removal of heavy metal ions using graphene-based nanomaterials: toxicity, roles of functional groups and mechanisms. Chemosphere, 248, 126008.
Alamri, H., AL-Shahrani, A., Bovero, E., Khaldi, T., Alabedi, G., Obaid, W., et al. 2018. Self-cleaning superhydrophobic epoxy coating based on fibrous silica-coated iron oxide magnetic nanoparticles. Journal of Colloid and Interface Science, 513, 349-356.
Anantha, M., Olivera, S., Hu, C., Jayanna, B., Reddy, N., Venkatesh, K., et al. 2020. Comparison of the photocatalytic, adsorption and electrochemical methods for the removal of cationic dyes from aqueous solutions. Environmental Technology and Innovation, 17, 100612.
Anbia, M., Kargosha, K. & Khoshbooei, S. 2015. Heavy metal ions removal from aqueous media by modified magnetic mesoporous silica MCM-48. Chemical Engineering Research and Design, 93, 779-788.
Abdollahi, S. N., Naderi, M. & Amoabediny, G. 2012. Synthesis and physicochemical characterization of tunable silica–gold nanoshells via seed growth method. Colloids and Surfaces A: Physicochemical and Engineering Aspects, 414, 345-351.
Awual, M. R. 2019. Mesoporous composite material for efficient lead (II) detection and removal from aqueous media. Journal of Environmental Chemical Engineering, 7, 103124.
Awual, M. R., Hasan, M. M. & Shahat, A. 2014. Functionalized novel mesoporous adsorbent for selective lead (II) ions monitoring and removal from wastewater. Sensors and Actuators B: Chemical, 203, 854-863.
Asuquo, E., Martin, A., Nzerem, P., Siperstein, F. & Fan, X. 2017. Adsorption of Cd(II) and Pb(II) ions from aqueous solutions using mesoporous activated carbon adsorbent: equilibrium, kinetics and characterisation studies. Journal of Environmental Chemical Engineering, 5, 679-698.
Bao, S., Li, K., Ning, P., Peng, J., Jin, X. & Tang, L. 2017. Highly effective removal of mercury and lead ions from wastewater by mercaptoamine-functionalised silica-coated magnetic nano-adsorbents: behaviours and mechanisms. Applied Surface Science, 393, 457-466.
Bayuo, J., Abukari, M. A. & Pelig-Ba, K. B. 2020. Optimization using central composite design (CCD) of response surface methodology (RSM) for biosorption of hexavalent chromium from aqueous media. Applied Water Science, 10, 1-12.
Betiha, M. A., Moustafa, Y. M., EL-Shahat, M. F. & Rafik, E. 2020. Polyvinylpyrrolidone-Aminopropyl-SBA-15 schiff Base hybrid for efficient removal of divalent heavy metal cations from wastewater. Journal of Hazardous Materials, 397, 122675.
Bhattacharya, S. 2021. Central composite design for response surface methodology and its application in pharmacy. In: Kayaroganam, P., Response Surface Methodology in Engineering Science. IntechOpen, India.
Cao, Y., Khan, A., Kurniawan, T. A., Soltani, R. & Albadarin, A. B. 2021. Synthesis of hierarchical micro-mesoporous LDH/MOF nanocomposite with in situ growth of UiO-66-(NH2) 2 Mof on the functionalized NiCo-LDH ultrathin sheets and its application for thallium (I) removal. Journal of Molecular Liquids, 336, 116189.
Cheng, S., Zhao, S., Guo, H., Xing, B., Liu, Y., Zhang, C. 2022. High-efficiency removal of lead/cadmium from wastewater by MgO modified biochar derived from crofton weed. Bioresource Technology, 343, 126081.
Cheraghipour, E. & Pakshir, M. 2020. Process optimization and modeling of Pb(II) ions adsorption on chitosan-conjugated magnetite nano-biocomposite using response surface methodology. Chemosphere, 260, 127560.
Clifford, D., Subramonian, S. & Sorg, T. J. 1986. Water treatment processes. III. Removing dissolved inorganic contaminants from water. Environmental Science and Technology, 20, 1072-1080.
Cui, H. Z., Li, Y. L., Liu, S., Zhang, J. F., Zhou, Q., Zhong, R., et al. 2017. Novel Pb(II) ion-imprinted materials based on bis-pyrazolyl functionalized mesoporous silica for the selective removal of Pb(II) in water samples. Microporous and Mesoporous Materials, 241, 165-177.
Da'na, E. & Sayari, A. 2012. Adsorption of heavy metals on amine-functionalized SBA-15 prepared by co-condensation: applications to real water samples. Desalination, 285, 62-67.
Dahlan, I., Azhar, E. E. M., Hassan, S. R., Aziz, H. A. & Hung, Y. T. 2022. Statistical modeling and optimization of process parameters for 2, 4-dichlorophenoxyacetic acid removal by using AC/PDMAEMA hydrogel adsorbent: comparison of different RSM designs and ANN training methods. Water, 14, 3061.
Dan, S., Kalantari, M., Kamyabi, A. & Soltani, M. 2021. Synthesis of chitosan-g-itaconic acid hydrogel as an antibacterial drug carrier: optimization through RSM-CCD. Polymer Bulletin, 1-24.
Dao, T. U. T., Nguyen, H. T. T., Nguyen, D. T. C., Le, H. T., Nguyen, H. T., Do, S. T., et al. 2020. Process optimization studies of Congo Red dye adsorption onto magnesium aluminium layered double hydroxide using response surface methodology. Polish Journal of Environmental Studies, 30, 679-687.
Dehghani, M. H., Karri, R. R., Yeganeh, Z. T., Mahvi, A. H., Nourmoradi, H., Salari, M., et al. 2020. Statistical modelling of endocrine disrupting compounds adsorption onto activated carbon prepared from wood using CCD-RSM and DE hybrid evolutionary optimization framework: comparison of linear vs non-linear isotherm and kinetic parameters. Journal of Molecular Liquids, 302, 112526.
Dhaliwal, S. S., Singh, J., Taneja, P. K. & Mandal, A. 2020. Remediation techniques for removal of heavy metals from the soil contaminated through different sources: a review. Environmental Science and Pollution Research, 27, 1319-1333.
Dinari, M., Soltani, R. & Mohammadnezhad, G. 2017. Kinetics and thermodynamic study on novel modified–mesoporous silica MCM-41/polymer matrix nanocomposites: effective adsorbents for trace CrVI removal. Journal of Chemical and Engineering Data, 62, 2316-2329.
Ding, H., Zhang, Y., Wang, S., Xu, J., Xu, S. & Li, G. 2012. Fe3O4@ SiO2 core/shell nanoparticles: the silica coating regulations with a single core for different core sizes and shell thicknesses. Chemistry of Materials, 24, 4572-4580.
Eltaweil, A., Mohamed, H. A., Abd EL-Monaem, E. M. & EL-Subruiti, G. 2020. Mesoporous magnetic biochar composite for enhanced adsorption of malachite green dye: characterization, adsorption kinetics, thermodynamics and isotherms. Advanced Powder Technology, 31, 1253-1263.
Elhamifar, D., Shojaeipoor, F. & Yari, O. 2016. Thiopropyl-containing ionic liquid based periodic mesoporous organosilica as a novel and efficient adsorbent for the removal of Hg (II) and Pb(II) ions from aqueous solutions. RSC Advances, 6, 58658-58666.
Faraji‐Khiavi, F., Jalilian, H., Heydari, S., Sadeghi, R., Saduqi, M., Razavinasab, S. A., et al. 2022. Utilization of health services among the elderly in Iran during the COVID‐19 outbreak: a cross‐sectional study. Health Science Reports, 5, e839.
Fattahi, M., Ezzatzadeh, E., Jalilian, R. & Taheri, A. 2021. Micro solid phase extraction of cadmium and lead on a new ion-imprinted hierarchical mesoporous polymer via dual-template method in river water and fish muscles: optimization by experimental design. Journal of Hazardous Materials, 403, 123716.
Fiyadh, S. S., Alsaadi, M. A., Jaafar, W. Z., Alomar, M. K., Fayaed, S. S., Mohd, N. S., et al. 2019. Review on heavy metal adsorption processes by carbon nanotubes. Journal of Cleaner Production, 230, 783-793.
Fooladgar, S., Teimouri, A. & Ghanavati Nasab, S. 2019. Highly efficient removal of lead ions from aqueous solutions using chitosan/rice husk ash/nano alumina with a focus on optimization by response surface methodology: isotherm, kinetic, and thermodynamic studies. Journal of Polymers and the Environment, 27, 1025-1042.
Guo, T., Bulin, C., Li, B., Zhao, Z., Yu, H., Sun, H., et al. 2018. Efficient removal of aqueous Pb(II) using partially reduced graphene oxide-Fe3O4. Adsorption Science and Technology, 36, 1031-1048.
Gupta, R., Gupta, S. K. & Pathak, D. D. 2019. Selective adsorption of toxic heavy metal ions using guanine-functionalized mesoporous silica [SBA-16-g] from aqueous solution. Microporous and Mesoporous Materials, 288, 109577.
Hasan, R., Chong, C., Bukhari, S., Jusoh, R. & Setiabudi, H. 2019. Effective removal of Pb(II) by low-cost fibrous silica KCC-1 synthesized from silica-rich rice husk ash. Journal of Industrial and Engineering Chemistry, 75, 262-270.
Hasan, R. & Setiabudi, H. 2019. Removal of Pb(II) from aqueous solution using KCC-1: optimization by response surface methodology (RSM). Journal of King Saud University-Science, 31, 1182-1188.
Hassan, M., Naidu, R., Du, J., Qi, F., Ahsan, M. A. & Liu, Y. 2022. Magnetic responsive mesoporous alginate/β-cyclodextrin polymer beads enhance selectivity and adsorption of heavy metal ions. International Journal of Biological Macromolecules, 207, 826-840.
He, H., Meng, X., Yue, Q., Yin, W., Gao, Y., Fang, P., et al. 2021. Thiol-ene click chemistry synthesis of a novel magnetic mesoporous silica/chitosan composite for selective Hg(II) capture and high catalytic activity of spent Hg(II) adsorbent. Chemical Engineering Journal, 405, 126743.
Hao, Y. M., Man, C. & Hu, Z. B. 2010. Effective removal of Cu(II) ions from aqueous solution by amino-functionalized magnetic nanoparticles. Journal of Hazardous Materials, 184, 392-399.
Heidari, A., Younesi, H. & Mehraban, Z. 2009. Removal of Ni(II), Cd(II), and Pb(II) from a ternary aqueous solution by amino functionalized mesoporous and nano mesoporous silica. Chemical Engineering Journal, 153, 70-79.
Huang, J., Ye, M., Qu, Y., Chu, L., Chen, R., He, Q. & Xu, D. 2012. Pb(II) removal from aqueous media by EDTA-modified mesoporous silica SBA-15. Journal of Colloid and Interface Science, 385, 137-146.
Izgi, M. S., Ece, M. Ş., Kazici, H. Ç. K., Şahi̇n, Ö. & Onat, E. 2020. Hydrogen production by using Ru nanoparticle decorated with Fe3O4@ SiO2–NH2 core-shell microspheres. International Journal of Hydrogen Energy, 45, 30415-30430.
Javaheri, F., Kheshti, Z., Ghasemi, S. & Altaee, A. 2019. Enhancement of Cd2+ removal from aqueous solution by multifunctional mesoporous silica: equilibrium isotherms and kinetics study. Separation and Purification Technology, 224, 199-208.
Javadian, H., Koutenaei, B. B., Shekarian, E., Sorkhrodi, F. Z., Khatti, R. & Toosi, M. 2017. Application of functionalized nano HMS type mesoporous silica with N-(2-aminoethyl)-3-aminopropyl methyldimethoxysilane as a suitable adsorbent for removal of Pb(II) from aqueous media and industrial wastewater. Journal of Saudi Chemical Society, 21, S219-S230.
Janighorban, M., Rasouli, N., Sohrabi, N. & Ghaedi, M. 2020. Response surface methodology for optimizing Cd(II) adsorption onto a novel chemically changed nano Zn2Al-layer double hydroxide. Advanced Journal of Chemistry Section A, 3, 701.
Jin, X., Li, K., Ning, P., Bao, S. & Tang, L. 2017. Removal of Cu(II) ions from aqueous solution by magnetic chitosan-tripolyphosphate modified silica-coated adsorbent: characterization and mechanisms. Water, Air and Soil Pollution, 228, 1-14.
Joshi, S., Bajpai, S. & Jana, S. 2020. Application of ANN and RSM on fluoride removal using chemically activated D. sissoo sawdust. Environmental Science and Pollution Research, 27, 17717-17729.
Khan, S. U., Farooqi, I. H., Usman, M. & Basheer, F. 2020. Energy efficient rapid removal of arsenic in an electrocoagulation reactor with hybrid Fe/Al electrodes: process optimization using CCD and kinetic modeling. Water, 12, 2876.
Khan, S. U., Mahtab, M. S. & Farooqi, I. H. 2021. Enhanced lead (II) removal with low energy consumption in an electrocoagulation column employing concentric electrodes: process optimisation by RSM using CCD. International Journal of Environmental Analytical Chemistry, 1-18.
Lapwanit, S., Trakulsujaritchok, T. & Nongkhai, P. N. 2016. Chelating magnetic copolymer composite modified by click reaction for removal of heavy metal ions from aqueous solution. Chemical Engineering Journal, 289, 286-295.
Li, S., Li, S., Wen, N., Wei, D. & Zhang, Y. 2021. Highly effective removal of lead and cadmium ions from wastewater by bifunctional magnetic mesoporous silica. Separation and Purification Technology, 265, 118341.
Li, Z., Tang, X., Liu, K., Huang, J., Peng, Q., Ao, M., et al. 2018. Fabrication of novel sandwich nanocomposite as an efficient and regenerable adsorbent for methylene blue and Pb(II) ion removal. Journal of Environmental Management, 218, 363-373.
Li, G., Zhao, Z., Liu, J. & Jiang, G. 2011a. Effective heavy metal removal from aqueous systems by thiol functionalized magnetic mesoporous silica. Journal of Hazardous Materials, 192, 277-283.
Li, W., Deng, Y., Wu, Z., Qian, X., Yang, J., Wang, Y., et al. 2011b. Hydrothermal etching assisted crystallization: a facile route to functional yolk-shell titanate microspheres with ultrathin nanosheets-assembled double shells. Journal of the American Chemical Society, 133, 15830-15833.
Liu, Y., Fu, R., Sun, Y., Zhou, X., Baig, S. A. & Xu, X. 2016. Multifunctional nanocomposites Fe3O4@ SiO2-EDTA for Pb(II) and Cu (II) removal from aqueous solutions. Applied Surface Science, 369, 267-276.
Liu, Y. & Liu, Y. J. 2008. Biosorption isotherms, kinetics and thermodynamics. Separation and Purification Technology, 61, 229-242.
Liu, Z., Haddad, M., Sauve, S. & Barbeau, B. 2021. Alleviating the burden of ion exchange brine in water treatment: from operational strategies to brine management. Water Research, 205, 117728.
Manzar, M. S., Khan, G., Dos Santos Lins, P. V., Zubair, M., Khan, S. U., Selvasembian, R., et al. 2021. RSM-CCD optimization approach for the adsorptive removal of Eriochrome Black T from aqueous system using steel slag-based adsorbent: characterization, isotherm, kinetic modeling and thermodynamic analysis. Journal of Molecular Liquids, 339, 116714.
Masue, Y., Loeppert, R. H. & Kramer, T. A. 2007. Arsenate and arsenite adsorption and desorption behavior on coprecipitated aluminum: iron hydroxides. Environmental Science and Technology, 41, 837-842.
Moghaddam, S. S., Moghaddam, M. A. & Arami, M. 2010. Coagulation/flocculation process for dye removal using sludge from water treatment plant: optimization through response surface methodology. Journal of Hazardous Materials, 175, 651-657.
Moosazade, M., Ashoori, R., Moghimi, H., Amani, M. A., Frontistis, Z. & Taheri, R. A. 2021. Electrochemical recovery to overcome direct osmosis concentrate-bearing lead: optimization of treatment process via RSM-CCD. Water, 13, 3136.
Mehdinia, A., Shegefti, S. & Shemirani, F. 2015. Removal of lead(II), copper(II) and zinc(II) ions from aqueous solutions using magnetic amine-functionalized mesoporous silica nanocomposites. Journal of the Brazilian Chemical Society, 26, 2249-2257.
Monier, M., Ayad, D., Wei, Y. & Sarhan, A. 2010. Adsorption of Cu (II), Co (II), and Ni (II) ions by modified magnetic chitosan chelating resin. Journal of Hazardous Materials, 177, 962-970.
Narayan, R., Nayak, U. Y., Raichur, A. M. & Garg, S. 2018. Mesoporous silica nanoparticles: a comprehensive review on synthesis and recent advances. Pharmaceutics, 10, 118.
Nasab, S. G., Semnani, A., Karimi, M., Yazd, M. J. & Cheshmekhezr, S. 2019. Synthesis of ion-imprinted polymer-decorated SBA-15 as a selective and efficient system for the removal and extraction of Cu(II) with focus on optimization by response surface methodology. Analyst, 144, 4596-4612.
Nowicka, A., Kucharska, A. Z., Sokół-Łętowska, A. & Fecka, I. 2019. Comparison of polyphenol content and antioxidant capacity of strawberry fruit from 90 cultivars of Fragaria× ananassa Duch. Food Chemistry, 270, 32-46.
Polshettiwar, V., Cha, D., Zhang, X. & Basset, J. M. 2010. High‐surface‐area silica nanospheres (KCC1) with a fibrous morphology. Angewandte Chemie International Edition, 49, 9652-9656.
Pongsumpun, P., Iwamoto, S. & Siripatrawan, U. 2020. Response surface methodology for optimization of cinnamon essential oil nanoemulsion with improved stability and antifungal activity. Ultrasonics Sonochemistry, 60, 104604.
Rahimi, T., Kahrizi, D., Feyzi, M., Ahmadvandi, H. R. & Mostafaei, M. 2021. Catalytic performance of MgO/Fe2O3-SiO2 core-shell magnetic nanocatalyst for biodiesel production of Camelina sativa seed oil: Optimization by RSM-CCD method. Industrial Crops and Products, 159, 113065.
Razmi, F. A., Ngadi, N., Wong, S., Inuwa, I. M. & Opotu, L. A. 2019. Kinetics, thermodynamics, isotherm and regeneration analysis of chitosan modified pandan adsorbent. Journal of Cleaner Production, 231, 98-109.
Reddy, K. R., Gomes, V. G. & Hassan, M. 2014. Carbon functionalized TiO2 nanofibers for high efficiency photocatalysis. Materials Research Express, 1, 015012.
Rott, E., Nouri, M., Meyer, C., Minke, R., Schneider, M., Mandel, K., et al. 2018. Removal of phosphonates from synthetic and industrial wastewater with reusable magnetic adsorbent particles. Water Research, 145, 608-617.
Salman, D., Juzsakova, T., Al-Mayyahi, M., Ákos, R., Mohsen, S., Ibrahim, R., et al. 2021. Synthesis, surface modification and characterization of magnetic Fe3O4@ SiO2 core-shell nanoparticles. Journal of Physics: Conference Series. IOP Publishing, 012039.
Samaniego, M. L., De Luna, M. D. G., Ong, D. C., Wan, M. W. & Lu, M. C. 2019. Isotherm and thermodynamic studies on the removal of sulfur from diesel fuel by mixing-assisted oxidative–adsorptive desulfurization technology. Energy and Fuels, 33, 1098-1105.
Šćiban, M., Klašnja, M. & Škrbić, B. 2006. Modified softwood sawdust as adsorbent of heavy metal ions from water. Journal of Hazardous Materials, 136, 266-271.
Singh, B. & Polshettiwar, V. 2016. Design of CO2 sorbents using functionalized fibrous nanosilica (KCC-1): insights into the effect of the silica morphology (KCC-1 vs. MCM-41). Journal of Materials Chemistry A, 4, 7005-7019.
Soltani, R., Dinari, M. & Mohammadnezhad, G. 2018. Ultrasonic-assisted synthesis of novel nanocomposite of poly (vinyl alcohol) and amino-modified MCM-41: a green adsorbent for Cd(II) removal. Ultrasonics Sonochemistry, 40, 533-542.
Soltani, R., Marjani, A. & Shirazian, S. 2019a. Facile one-pot synthesis of thiol-functionalized mesoporous silica submicrospheres for Tl(I) adsorption: isotherm, kinetic and thermodynamic studies. Journal of Hazardous Materials, 371, 146-155.
Soltani, R., Marjani, A. & Shirazian, S. 2019b. Shell-in-shell monodispersed triamine-functionalized SiO2 hollow microspheres with micro-mesostructured shells for highly efficient removal of heavy metals from aqueous solutions. Journal of Environmental Chemical Engineering, 7, 102832.
Soltani, R., Marjani, A., Soltani, R. & Shirazian, S. 2020. Hierarchical multi-shell hollow micro–meso–macroporous silica for Cr(VI) adsorption. Scientific Reports, 10, 1-12.
Sun, D., Zhao, Y., Cao, Y., Liu, M., Zhang, Y., Zhao, L., et al. 2020. Investigation on the interaction mechanism of the solvent extraction for mercaptan removal from liquefied petroleum gas. Energy and Fuels, 34, 4788-4798.
Sun, Z., Cui, G., Li, H., Liu, Y., Tian, Y. & Yan, S. 2016. Multifunctional optical sensing probes based on organic–inorganic hybrid composites. Journal of Materials Chemistry B, 4, 5194-5216.
Shahbazi, A., Younesi, H. & Badiei, A. 2011. Functionalized SBA-15 mesoporous silica by melamine-based dendrimer amines for adsorptive characteristics of Pb(II), Cu(II) and Cd(II) heavy metal ions in batch and fixed bed column. Chemical Engineering Journal, 168, 505-518.
Shi, Z., Xu, C., Guan, H., Li, L., Fan, L., Wang, Y., et al. 2018. Magnetic metal organic frameworks (MOFs) composite for removal of lead and malachite green in wastewater. Colloids and Surfaces A: Physicochemical and Engineering Aspects, 539, 382-390.
Saeidi, N., Parvini, M. & Niavarani, Z. 2015. High surface area and mesoporous graphene/activated carbon composite for adsorption of Pb(II) from wastewater. Journal of Environmental Chemical Engineering, 3, 2697-2706.
Taseidifar, M., Ziaee, M., Pashley, R. M. & Ninham, B. W. 2019. Ion flotation removal of a range of contaminant ions from drinking water. Journal of Environmental Chemical Engineering, 7, 103263.
Topal, M. & Topal, E. I. A. 2020. Optimization of tetracycline removal with chitosan obtained from mussel shells using RSM. Journal of Industrial and Engineering Chemistry, 84, 315-321.
Torğut, G., Tanyol, M. & Meşe, Z. 2020. Modeling and optimization of indigo carmine adsorption from aqueous solutions using a novel polymer adsorbent: RSM-CCD. Chemical Engineering Communications, 207, 1157-1170.
Venkateswarlu, S., Kumar, B. N., Prathima, B., Subbarao, Y. & Jyothi, N. V. V. 2019. A novel green synthesis of Fe3O4 magnetic nanorods using Punica Granatum rind extract and its application for removal of Pb(II) from aqueous environment. Arabian Journal of Chemistry, 12, 588-596.
Vickers, N. J. 2017. Animal communication: when i’m calling you, will you answer too? Current Biology, 27, R713-R715.
Vieira, W. T., De Farias, M. B., Spaolonzi, M. P., DA Silva, M. G. C. & Vieira, M. G. A. 2020. Removal of endocrine disruptors in waters by adsorption, membrane filtration and biodegradation. a review. Environmental Chemistry Letters, 18, 1113-1143.
Vij, R. K., Janani, V. A., Subramanian, D., Mistry, C. R., Devaraj, G. & Pandian, S. 2021. Equilibrium, kinetic and thermodynamic studies for the removal of Reactive Red dye 120 using Hydrilla verticillata biomass: a batch and column study. Environmental Technology and Innovation, 24, 102009.
Vojoudi, H., Badiei, A., Bahar, S., Ziarani, G. M., Faridbod, F. & Ganjali, M. R. 2017. A new nano-sorbent for fast and efficient removal of heavy metals from aqueous solutions based on Modification of magnetic mesoporous silica nanospheres. Journal of Magnetism and Magnetic Materials, 441, 193-203.
Wang, J., Tong, X., Chen, Y., Sun, T., Liang, L. & Wang, C. 2020a. Enhanced removal of Cr(III) in high salt organic wastewater by EDTA modified magnetic mesoporous silica. Microporous and Mesoporous Materials, 303, 110262.
Wang, N., Yang, D., Wang, X., Yu, S., Wang, H., Wen, T., et al. 2018. Highly efficient Pb(II) and Cu(II) removal using hollow Fe3O4@ PDA nanoparticles with excellent application capability and reusability. Inorganic Chemistry Frontiers, 5, 2174-2182.
Wang, P., Shen, T., Li, X., Tang, Y. & Li, Y. 2020b. Magnetic mesoporous calcium carbonate-based nanocomposites for the removal of toxic Pb(II) and Cd(II) ions from water. ACS Applied Nano Materials, 3, 1272-1281.
Wu, Y., Pang, H., Liu, Y., Wang, X., Yu, S., Fu, D., et al. 2019. Environmental remediation of heavy metal ions by novel-nanomaterials: a review. Environmental Pollution, 246, 608-620.
Wang, L., Sun, Y., Wang, J., Wang, J., Yu, A., Zhang, H., et al. 2011. Preparation of surface plasmon resonance biosensor based on magnetic core/shell Fe3O4/SiO2 and Fe3O4/Ag/SiO2 nanoparticles. Colloids and Surfaces B: Biointerfaces, 84, 484-490.
Wang, S., Wang, K., Dai, C., Shi, H. & Li, J. 2015. Adsorption of Pb2+ on amino-functionalized core–shell magnetic mesoporous SBA-15 silica composite. Chemical Engineering Journal, 262, 897-903.
Xin, X., Wei, Q., Yang, J., Yan, L., Feng, R., Chen, et al. 2012. Highly efficient removal of heavy metal ions by amine-functionalized mesoporous Fe3O4 nanoparticles. Chemical Engineering Journal, 184, 132-140.
Wu, X. W., Ma, H. W., Yang, J., Wang, F. J. & Li, Z. H. 2012. Adsorption of Pb(II) from aqueous solution by a poly-elemental mesoporous adsorbent. Applied Surface Science, 258, 5516-5521.
Xu, J., Cao, Z., Zhang, Y., Yuan, Z., Lou, Z., Xu, X., et al. 2018. A review of functionalized carbon nanotubes and graphene for heavy metal adsorption from water: preparation, application, and mechanism. Chemosphere, 195, 351-364.
Xu, P., Wang, H., Tong, R., Du, Q. & Zhong, W. 2006. Preparation and morphology of SiO2/PMMA nanohybrids by microemulsion polymerization. Colloid and Polymer Science, 284, 755-762.
Xu, Z., Feng, Y., Liu, X., Guan, M., Zhao, C. & Zhang, H. 2010. Synthesis and characterization of Fe3O4@ SiO2@ poly-l-alanine, peptide brush–magnetic microspheres through NCA chemistry for drug delivery and enrichment of BSA. Colloids and Surfaces B: Biointerfaces, 81, 503-507.
Yang, S., Zong, P., Ren, X., Wang, Q. & Wang, X. 2012. Rapid and highly efficient preconcentration of Eu(III) by core–shell structured Fe3O4@ humic acid magnetic nanoparticles. ACS Applied Materials and Interfaces, 4, 6891-6900.
Yang, G., Tang, L., Zeng, G., Cai, Y., Tang, J., Pang, Y., et al. 2015. Simultaneous removal of lead and phenol contamination from water by nitrogen-functionalized magnetic ordered mesoporous carbon. Chemical Engineering Journal, 259, 854-864.
Yu, K., Zhang, X., Tong, H., Yan, X. & Liu, S. 2013. Synthesis of fibrous monodisperse core–shell Fe3O4/SiO2/KCC-1. Materials Letters, 106, 151-154.
Yuna, Z. 2016. Review of the natural, modified, and synthetic zeolites for heavy metals removal from wastewater. Environmental Engineering Science, 33, 443-454.
Zhang, F., Shi, Y., Zhao, Z., Ma, B., Wei, L. & Lu, L. 2014. Amino-functionalized Fe3O4/SiO2 magnetic submicron composites and In 3+ ion adsorption properties. Journal of Materials Science, 49, 3478-3483.
Zhang, J., Zhai, S., Li, S., Xiao, Z., Song, Y., An, Q., et   al. 2013. Pb(II) removal of Fe3O4@ SiO2–NH2 core–shell nanomaterials prepared via a controllable sol–gel process. Chemical Engineering Journal, 215, 461-471.
Zhao, W., Cui, B., Peng, H., Qiu, H. & Wang, Y. 2015. Novel method to investigate the interaction force between etoposide and APTES-functionalized Fe3O4@nSiO2@ mSiO2 nanocarrier for drug loading and release processes. The Journal of Physical Chemistry C, 119, 4379-4386.
Zhou, J., Liu, Y., Zhou, X., Ren, J. & Zhong, C. 2018. Magnetic multi-porous bio-adsorbent modified with amino siloxane for fast removal of Pb(II) from aqueous solution. Applied Surface Science, 427, 976-985.