本研究以偏高嶺土合成多孔海綿狀無機聚合物塊材，應用作為Sr2+之吸附劑，預期可應用於大型河川汙染整治及工業廢水處理。本研究主要分為四大部分，第一部分為探討無機聚合物的適當發泡及成孔參數，將熱處理後所得之偏高嶺土作為無機聚合物之前驅物，利用鹼活化劑NaOH在結構中置入大量可交換之Na離子，聚合過程中使用H2O2作為發泡劑及界面活性劑Triton X-100作為孔隙成形劑，用以提高無機聚合物之孔隙率及滲透效率，製成海綿狀多孔吸附劑。實驗結果顯示，改變NaOH濃度可有效改變結構中Na含量，而透過發泡劑及成孔劑的添加可有效提升孔隙率及滲透率，多孔無機聚合物之孔隙率最高可達86.20%，滲透係數最高可達2.65×10-2 cm/s，使用1000 ppm之Sr2+模擬液將未發泡及發泡後之無機聚合物對Sr2+進行去除測試，發現發泡後之多孔無機聚合物對Sr2+去除率由30.3 %有效提升至59.4 %，證明提升樣品孔隙率對吸附效能有所幫助。
第二部分為探討H2O2、Triton X-100及NaOH濃度對於無機聚合物結構及吸附效能影響，實驗結果顯示，提高發泡劑H2O2比例，可提升孔隙率，但也容易造成大量孔洞合併成大孔，使得大孔結構比例。添加Triton X-100可使整體孔隙變更細小且均勻，雖會降低孔隙率，但可提升內部介孔結構比例及孔洞連通性。提高NaOH濃度可催化H2O2反應，使孔隙率提高，另一方面也使Si、Al離子的溶出再聚合作用更完整，Al-O-Si鍵結比例提高，抗壓強度提升至3.68 Mpa。在高濃度NaOH（10 M）同時亦可增加可交換之Na離子含量，對於Sr離子的吸附效率有提升的效果。
第三部分則是探討上述多孔無機聚合物對於Sr2+批次吸附效率及連續式管柱吸附試驗，並探討其吸附機制。實驗結果顯示，多孔無機聚合物對於Sr2+之批次吸附量最高可達89.05 mg/g，於連續式管柱吸附試驗中最大吸附量為46.91 mg/g，不僅於批次吸附上極佔優勢，於連續式吸附也有優良吸附效能。而連續式管柱吸附效率受流速及接觸時間影響，使連續吸附效率略低於批次吸附效率。從吸附機制的研究結果顯示，多孔無機聚合物對Sr2+的吸附機制以離子交換為主要離子吸附方式，化學沉澱量影響甚少，其中影響吸附因素有介孔比例的提升，孔徑越小，比表面積就越大，吸附能力就愈佳；離子交換主要以Al-O-Na形式鍵結之Na離子作為主要交換位址；殘餘之NaOH會造成Sr(OH)2沉澱。
第四部分為多孔無機聚合物對於重金屬離子Pb2+之批次吸附效能評估，並以含Cu2+、Ni2+及Co2+、B離子之工業廢水進行吸附測試，評估實廠應用價值。實驗結果顯示，多孔無機聚合物對於Pb2+有極高之去除率，但去除機制應為化學沉澱反應，因多孔無機聚合物殘餘之OH-而形成Pb(OH)2沈澱。於含Co、B工業廢水之吸附測試上，對於Co2+之去除率可達90.49%，而對B離子不具去除能力；於含Ni2+及Cu2+之高酸度( pH< 2 )工業廢水吸附測試上，多孔無機聚合物對於含60 ppm的Ni2+可達68.65%的去除率，而對含Cu2+之工業廢水則因廢水中共存之 Na+及K+離子產生競爭性行為，對Cu2+的去除效率並不理想。

關鍵字 : 高嶺土、無機聚合物、發泡、孔隙、Sr2+、吸附

This research is devoted to the removal and treatment of Sr2+ ions in nuclear wastewater. Geopolymer is a building material with great application potential in recent years, with excellent mechanical properties and chemical stability. This research improves the porosity and permeability of geopolymers through the addition of foaming agents and uses the alkali activator NaOH to insert a large amount of exchangeable Na ions in the structure. Application as a sponge-like porous adsorbent is expected to be applied to large-scale river pollution remediation and industrial wastewater treatment. This research uses kaolinite as the precursor, geopolymer as the base material, H2O2 as the foaming agent, and Triton X-100 as the stabilizer. Discuss the influence of process parameters on the pore characteristics of synthetic geopolymers and use Sr2+ ions as the adsorption targets to explore the adsorption characteristics of porous geopolymers. The results revealed that the porous geopolymer has a maximum porosity of 86.20% and a permeability coefficient of 2.65×10-2 cm/s affected by the foaming treatment. The best compressive strength is 3.68 Mpa, which is affected by the increase in Al-O-Si bonding ratio. The adsorption mechanism is affected by pores and Na content. The maximum adsorption capacity in batches is 89.05 mg/g, and the maximum adsorption capacity in continuous column adsorption is 46.91 mg/g. Not only is it extremely dominant in batch adsorption, it also has excellent adsorption performance in continuous adsorption.

Key words : Kaolinite、Geopolymer、Foam、Porous、Strontium、Adsorption

[1] T.H. Tsai, H.W. Chou, Y.F. Wu (2020) Removal of nickel from chemical plating waste solution through precipitation and production of microsized nickel hydroxide particles. Separation and Purification Technology, 251, 117315.
[2] S. Hao, Z. Jia, J. Wen, S. Li, W. Peng, R. Huang, X. Xu. (2021) Progress in adsorptive membranes for separation – A review. Separation and Purification Technology, 255, 117772.
[3] S. Chellammal, S. Raghu, P. Kalaiselvi, G. Subramanian (2010) Electrolytic recovery of dilute copper from a mixed industrial effluent of high strength COD. Journal of Hazardous Materials, 180, 91-97
[4] I. Mironyuk, T. Tatarchuk, H. Vasylyeva, M. Naushad, I. Mykytyn (2019) Adsorption of Sr(II) cations onto phosphated mesoporous titanium dioxide: Mechanism, isotherm and kinetics studies. Journal of Environmental Chemical Engineering, 7, 103430.
[5] M. Arnould, C. Clement, D. Gouvenot, R. Struillou (1991) New sorbing grouts for radioactive and toxic heavy metals. Engineering Geology, 30, 127-139
[6] X. Li, Y. Sun, N. Liu, Z. Chuai, L. Tang, J. Zhang (2020) Invasion of Pb2+ into montmorillonite-illite clay and the response of interlayer K+ and water Applied Clay Science, 194, 105693
[7] M. Gutierrez, H.R. Fuentes (1991) Competitive Adsorption of Cesium, Cobalt and Strontium in Conditioned Clayey Soil Suspensions. Journal of Environmental Radioactivity, 13, 271-282
[8] Y. Zhang, X. Song, P. Zhang, H. Gao, C. Ou, X. Kong (2020) Production of activated carbons from four wastes via one-step activation and their applications in Pb2þ adsorption: Insight of ash content. Chemosphere, 245, 125587
[9] S. Pap, J. Radonic, S. Trifunovic, D. Adamovic, I. Mihajlovic, M.V. Miloradov, M.T. Sekulic (2016) Evaluation of the adsorption potential of eco-friendly activated carbon prepared from cherry kernels for the removal of Pb2+, Cd2+ and Ni2+ from aqueous wastes. Journal of Environmental Management, 184, 297-306
[10] M. Caccin, F. Giacobbo, M.D. Ros, L. Besozzi M. Mariani (2013) Adsorption of uranium, cesium and strontium onto coconut shell activated carbon. Journal of Radioanalytical and Nuclear Chemistry, 297(1), 9-18
[11] T.Y. Kim, S.S. An, W.G. Shim, J.W. Lee, S.Y. Cho, J.H. Kim (2015) Adsorption and energetic heterogeneity properties of cesium ions on ion exchange resin. Journal of Industrial and Engineering Chemistry, 27, 260-267
[12] Y. Aşçı, Ş. Kaya (2014) Removal of cobalt ions from water by ion-exchange method. Desalination and Water Treatment, 52, 267-273
[13] S. Chena, J. Hu, S. Han, Y. Guo, N. Belzile, T. Deng (2020) A review on emerging composite materials for cesium adsorption and environmental remediation on the latest decade. Separation and Purification Technology, 251, 117340
[14] T.W. Cheng, M.L. Lee, M.S. Ko, T.H. Ueng, S.F. Yang (2012) The Heavy Metal Adsorption Characteristics on Metakaolin-Based Geopolymer. Applied Clay Science, 56, 90-96
[15] S. Andrejkovičová, A. Sudagar, J. Rocha, C. Patinha, W. Hajjaji, E.F. Silva, A. Velosa, F. Rocha (2016) The effect of natural zeolite on microstructure, mechanical and heavy metals adsorption properties of metakaolin based geopolymers. Applied Clay Science, 126, 141-152
[16] Q. Tang, Y. Ge, K. Wang, Y. He, X. Cui (2015) Preparation and characterization of porous metakaolin-based inorganic polymer spheres as an adsorbent. Materials and Design, 88, 1244-1249
[17] İ. Kara, D. Yilmazer, S. Tunali, Akar (2017) Metakaolin based geopolymer as an effective adsorbent for adsorption of zinc (II) and nickel (II) ions from aqueous solutions. Applied Clay Science, 139, 54-63
[18] A. Maleki, M. Mohammad, Z. Emdadi, N. Asim, M. Azizi, J. Safaei (2020) Adsorbent materials based on a geopolymer paste for dye removal from aqueous solutions. Arabian Journal of Chemistry, 13, 3017-3025
[19] H. Lei, Y. Muhammad, K. Wang, M. Yi, C. He, Y. Wei, T. Fujita (2021) Facile fabrication of metakaolin/slag-based zeolite microspheres (M/SZMs) geopolymer for the efficient remediation of Cs+ and Sr2+ from aqueous media. Journal of Hazardous Materials, 406, 124292
[20] 黃怡萱，(2019)。鹼活化高嶺土對Sr2+及Co2+離子之吸附特性研究，國立成功大學資源工程所，碩士論文。
[21] S. Wanga, S. Ning, W. Zhang, S. Zhang, J. Zhou, X. Wang, Y. Wei. (2020). Synthesis of carboxyl group functionalized silica composite resin for strontium removal. Materials & Design, 185(5), 108224.
[22] X. Zhao, L. Song, Z. Zhang, R. Wang, J. Fu. (2011). Adsorption investigation of MA-DTPA chelating resin for Ni (II) and Cu (II) using experimental and DFT methods. Journal of Molecular Structure,986(1-3), 68-74.
[23] L. Wanga, L. Yang, Y. Li, Y. Zhang, X. Ma, Z. Ye (2010) Study on adsorption mechanism of Pb (II) and Cu (II) in aqueous solution using PS-EDTA resin. Chemical Engineering Journal,163(3),364-372.
[24] H. Hamad, Z. Ezzeddine, F. Lakis, H. Rammal, M. Srour, A. Hijazi (2016) An insight into the removal of Cu (II) and Pb (II) by aminopropyl-modified mesoporous carbon CMK-3: Adsorption capacity and mechanism. Materials Chemistry and Physics,178(1),57-64
[25] S. Wang, J. H. Kwak, M. S. Islamd, M. A. Naeth, M. G. E. Din, S. X. Chang (2020) Biochar properties and lead (II) adsorption capacity depend on feedstock type, pyrolysis temperature, and steam activation. Science of The Total Environment,712(10).
[26] I. Smičiklas, S. Dimović, I. Plećaš (2007) Removal of Cs1+, Sr2+ and Co2+ from aqueous solutions by adsorption on natural clinoptilolite. Applied Clay Science 35, 139–144
[27] Y. Lia, P. Baia, Y. Yana, W. Yana, W. Shib, R. Xu (2019) Removal of Zn2+, Pb2+, Cd2+, and Cu2+ from aqueous solution by synthetic clinoptilolite. Microporous and Mesoporous Materials, 273, 203-211
[28] P. Arabkhani, A. Asfaram, M. Ateia (2020) Easy-to-prepare graphene oxide/sodium montmorillonite polymer nanocomposite with enhanced adsorption performance. Journal of Water Process Engineering,38,101651
[29] S. Chen, Z. Zang, S. Zhang, G. Ouyang, R. Han (2020) Preparation of MIL-100(Fe) and multi-walled carbon nanotubes nanocomposite with high adsorption capacity towards Oxytetracycline from solution. Journal of Environmental Chemical Engineering,20,104780
[30] S. Dadfarnia, A. M. H. Shabani, S. E. Moradi, S. Emami (2015) Methyl red removal from water by iron based metal-organic frameworks loaded onto iron oxide nanoparticle adsorbent. Applied Surface Science,330(1),85-93
[31] P. Asgari, S. H. Mousavi, H. Aghayan, H. Ghasemi, T. Yousefi (2019) Nd-BTC metal-organic framework (MOF) synthesis, characterization and investigation on its adsorption behavior toward cesium and strontium ions. Microchemical Journal,150,104188
[32] H. Liao, Y. Li, H. Li, B. Li, Y. Zhou, D. Liu, X. Wang (2020) Efficiency and mechanism of amidoxime-modified X-type zeolite (AO-XZ) for Cs+ adsorption. Chemical Physics Letters,741(16),137084
[33] Y. A. Mustafa, M. J. Zaiter (2011) Treatment of radioactive liquid waste (Co-60) by sorption on Zeolite Na-A prepared from Iraqi kaolin. Journal of Hazardous Materials,196(30),228-233
[34] M. Aurélie, W. Evelyne, B. Yves, G. Agnès (2012) The sorption behaviour of synthetic sodium nonatitanate and zeolite A for removing radioactive strontium from aqueous wastes. Separation and Purification Technology,96(21),81-88
[35] S. Kwon, C. Kim, E. Han, H. Lee, H. S. Cho, M. Cho (2020) Relationship between zeolite structure and capture capability for radioactive cesium and strontium. Journal of Hazardous Material,29,124419
[36] H. Long, P. Wu, N. Zhu (2013) Evaluation of Cs+ removal from aqueous solution by adsorption on ethylamine-modified montmorillonite. Chemical Engineering Journal,225(1),237-244
[37] D. Liu, S. Deng, M. Vakili, R. Du, L. Tao (2019) Fast and high adsorption of Ni (II) on vermiculite-based nanoscale hydrated zirconium oxides. Chemical Engineering Journal,360(15),1150-1157
[38] 陳皓馨，天然膨潤土改質與膠囊化處理及其對Sr2+及Cs+離子之吸附特性研究，國立成功大學資源工程研究所，碩士論文 (2017)
[39] Q. Tang, Y. Ge, K. Wang, Y. He, X. Cui (2015) Preparation and characterization of porous metakaolin-based inorganic polymer spheres as an adsorbent. Material design, 88, 2015, 1244-1249
[40] R. M. Novais, L. H. Buruberri, M. P. Seabra, J. A. Labrincha (2016) Novel porous fly-ash containing geopolymer monoliths for lead adsorption from wastewaters. Journal Hazardous Materials, 318, 2016, 631–640
[41] F. J. Lopez, S. Sugita, T. Kobayashi (2013) Cesium-adsorbent Geopolymer Foams Based on Silica from Rice Husk and Metakaolin. Chemistry Letters, 43(1),128-130.
[42] L. Darmayantia, G. T. M. Kadjac, S. Notodarmojob, E. Damanhuri, R. R. Mukti (2019) Structural alteration within fly ash-based geopolymers governing the adsorption of Cu2+ from aqueous environment: Effect of alkali activation. Journal of Hazardous Materials, 377, 305-314
[43] F. Demir, E. M. Derun (2019) Modelling and optimization of gold mine tailings based geopolymer by using response surface method and its application in Pb2+ removal. Journal of Cleaner Production, 237, 117766
[44] H. Wang, H. Li, F. Yan (2005) Synthesis and mechanical properties of metakaolinite-based geopolymer. Coloids and Surfaces,268,1-6
[45] M.S. Muñiz-Villarreal, A. Manzano-Ramírez, S. Sampieri-Bulbarela, J. Ramón Gasca-Tirado, J.L. Reyes-Araiza, J.C. Rubio-Ávalos, J.J. Pérez-Bueno (2011) The effect of temperature on the geopolymerization process of a metakaolin-based geopolymer. Materials Letters,65,995-998
[46] O. A. Hodhod, S. E. Alharthy, S. M. Bakr (2020) Physical and mechanical properties for metakaolin geopolymer bricks. Construction and Building Materials, 265, 120217
[47] B. B. Sabir, S. Wild, J. Bai (2001) Metakaolin and calcined clays as pozzolans for concrete: a review. Cement and Concrete Composites, 23, 441-454
[48] A. K. Chakraborty (2003) DTA study of preheated kaolinite in the mullite formation region. Thermochimica Acta, 398, 203-209
[49] E. Dmitrieva, E. Potapova (2020) Effect of heat-treated polymineral clays on the properties of portland cement paste. Materials Today: Proceedings
[50] C. Belver, M. A. B. Muñoz, M. A. Vicente (2002) Chemical activation of a kaolinite under acid and alkalinite conditions. Chemistry of Materials,14(5),2033-2043
[51] H. Ailar, T. Ngo, P. Mendis, T. Nguyen, A. Kashani, J. S. J. Deventer (2017) Pore characteristics in one-part mix geopolymers foamed by H2O2: The impact of mix design. Materials and Design,130,381-391
[52] R. M. Novais, G. Ascensão, L. H. Buruberri, L. Senff, J. A. Labrincha (2016) Influence of blowing agent on the fresh- and hardened-state properties of lightweight geopolymers. Materials and Design,108,551-559
[53] S. Petlitckaia, A. Poulesquen (2019) Design of lightweight metakaolin based geopolymer foamed with hydrogen peroxide. Ceramics International,45,1322-1330
[54] V. Ducman, L. Korat.(2016). Characterization of geopolymer fly-ash based foams obtained with the addition of Al powder or H2O2 as foaming agents. Materials Characterization,113,207-213
[55] 胡閔茜，(2013)。以離子交換樹脂分離藍泥浸漬液中釩、鉬之研究，國立成功大學資源工程所，碩士論文。
[56] S. A. Rasaki, Z. Bingxue, R. Guarecuco, T. Thomas, Y. Minghui (2019) Geopolymer for use in heavy metals adsorption, and advanced oxidative processes: A critical review. Journal of Cleaner Production,213,42-58
[57] L. Bouna, A. A. E. Fakir, A. Benlhachemi, K. Draoui, M. Ezahri, B. Bakiz, S. Villain, F. Guinneton, N. Elalem (2020) Synthesis and characterization of mesoporous geopolymer based on Moroccan kaolinite rich clay. Applied Clay Science,196,105764
[58] S. Aditi, B. P. Gangwar, J. M. Gayathry (2017) CTAB modified large surface area nanoporous geopolymer with high adsorption capacity for copper ion removal. Applied Clay Science,150,106-114
[59] C. Bai, A. Conte, P. Colombo (2017) Open-cell phosphate-based geopolymer foams by frothing. Materials Letters,188,379-382
[60] F. Jacques, M. Cellier, P. Y. Vuillaume (2020) Macroporous geopolymers designed for facile polymers post-infusion. Cement and Concrete Composites,110,103591
[61] L. Korat, V. Ducman (2017) The influence of the stabilizing agent SDS on porosity development in alkali-activated fly-ash based foams. Cement and Concrete Composites, 80168-174
[62] P. Viengsai, S. Wattanasiriwech, T. W. Cheng, D. Wattanasiriwech (2020) Effects of surfactant on thermo-mechanical behavior of geopolymer foam paste made with sodium perborate foaming agent. Construction and Building Materials, 243, 118282
[63] F. Xu, G. Gu, W. Zhang, H. Wang, X. Huang, J. Zhu (2018) Pore structure analysis and properties evaluations of fly ash-based geopolymer foams by chemical foaming method. Ceramics International,44,19989-19997.
[64] A. R. Studart, U. T. Gonzenbach, E. Tervoort, L. J. Gauckler (2006) Processing Routes to Macroporous Ceramics: A Review. Journal Ceramics, 89, 1771-1789.
[65] J. Davidovits (1991) Geopolymers : Inorganic polymerie new materials. Journal of Thermal Analysis, 37, 1633-1656
[66] J. Davidovits (2008) Geopolymer chemistry and applications, Institut Geopolymere, St. Quentin, France.
[67] 呂軒志，王泰典，鄭大偉，翁祖炘，(2011)。無機聚合物力學特性與結構特徵之關係探討，Conference on Resources Engineering,21-22。
[68] X. Zhu, D. Yan, H. Fang, S. Chen, H. Ye (2021) Early-stage geopolymerization revealed by 27Al and 29Si nuclear magnetic resonance spectroscopy based on vacuum dehydration. Construction and Building Materials, 266, 121114。
[69] T. R. Barbosa, E. L. Foletto, G. L. Dotto, S. L. Jahn (2018) Preparation of mesoporous geopolymer using metakaolin and rice husk ash as synthesis precursors and its use as potential adsorbent to remove organic dye from aqueous solutions. Ceramics International, 44, 416-423
[70] D. M. Juela (2021) Comments on Treatment of malachite green dye containing solution using bio-degradable sodium alginate/NaOH treated activated sugarcane baggsse charcoal beads: Batch, optimization using response surface methodology and continuous fixed bed column study” and “Adsorption and oxidation of ciprofloxacin in a fixed bed column using activated sludge derived activated carbon. Journal of Environmental Management, 281, 111815
[71] 戴詩潔，鄭大偉，(2005)。高嶺石鋁矽酸鹽聚和材料之研究。國立臺北科技大學材料及資源工程研究所，82-88
[72] Z. Ji, M. Li, L. Su, Y. Pei (2020) Porosity, mechanical strength and structure of waste-based geopolymer foams by different stabilizing agents. Construction and Building Materials, 258, 119555
[73] M. Zhang, M. Zhao, G. Zhang, J. M. Sietins, S. G. Focil, M. S. Pepi, Y. Xuf, M. Tao (2018) Cement and Concrete Composites, 93, 175-185
[74] S. Chitsaz, A. Tarighat (2021) Estimation of the modulus of elasticity of N-A-S-H and slag-based geopolymer structures containing calcium and magnesium ions as impurities using molecular dynamics simulations. Ceramics International, 47, 6424-6433
[75] 鄭大偉，(2010)。無機聚合技術的發展應用及回顧。
[76] P. Duxson, J. L. Provis, G. C. Lukey, S. W. Mallicoat, W. M. Kriven, J. S.J. Deventer (2005) Understanding the relationship between geopolymer composition, microstructure and mechanical properties. Colloids and Surfaces, 269, 47-58
[77] P. Szabó, B. Zsirka, D. Fertig, E. Horváth, T. Csizmadia, J. Kristóf (2017) Delaminated kaolinites as potential photocatalysts: Tracking degradation of Na-benzenesulfonate test compound adsorbed on the dry surface of kaolinite nanostructures. Catalysis Today, 287, 37-44
[78] Z. Cao, Q. Wang, H. Cheng (2021) Recent advances in kaolinite-based material for photocatalysts. Journal Pre-proof, 6086
[79] Klein C., Hurlbut C. S. Jr (1993) Manual of Mineralogy,21"edition.
[80] 黃任偉，(2002)，粒狀氫氧化鐵吸附地下水中砷的研究，國立成功大學環境工程所，碩士論文。
[81] S. Brunauer, L. S. Deming, W. E. Deming, E. Teller (1940) On a Theory of the van der Waals Adsorption of Gases. Journal of the American Chemical Society, 62(7),1723-1732
[82] H. C. Thomas (1948) Chromatography : A problem in kinetics. Sterling Chemistry Laboratory, Yale University, New Haven, Connecticut
[83] 黃安斌，大地工程原理，基礎工程學，4，166-168
[84] E. Eren, B. Afsin (2008) An investigation of Cu (II) adsorption by raw and acid-activated bentonite: A combined potentiometric, thermodynamic, XRD, IR, DTA study. Journal of Hazardous Materials, 151, 682-691
[85] P. Stathi, K. Litina, D. Gournis, T. S. Giannopoulos, Y. Deligiannakis (2007) Physicochemical study of novel organoclays as heavy metal ion adsorbents for environmental remediation. Journal of Colloid and Interface Science, 316, 298-309
[86] H. T. Ng, C. Y. Heah,Y. M. Liew, M. M. A. B. Abdullah, E. H. Kong, M. R. Hasniyati, Y. S. Ng (2021) Formulation, mechanical properties and phase analysis of fly ash geopolymer with ladle furnace slag replacement. Journal of Materials and technology, 12, 1212-1226
[87] H. Wang, H. Li, F. Yan (2005) Synthesis and tribological behavior of metakaolinite-based geopolymer composites. Materials Letters 59,3976-3981
[88] C. F. Pereira, Y. L. Galiano, M. P. Clemente, C. Leiva, F. Arroyo, R. Villegas, L.F. Vilches (2018) Immobilization of heavy metals (Cd, Ni or Pb) using aluminate geopolymers. Materials Letters, 227, 184-186
[89] R. Ram, L. Morrisroe, B. Etschmann, J. Vaughan, J. Brugger (2021) Lead (Pb) sorption and co-precipitation on natural sulfide, sulfate and oxide minerals under environmental conditions. Minerals Engineering, 163, 106801
[90] Y. Chen, J. Tang, S. Wang, L. Zhang (2021) Ninhydrin-functionalized chitosan for selective removal of Pb(II) ions: Characterization and adsorption performance. International Journal of Biological Macromolecules, 177(30), 29-39
[91] S. Shi, Q. Dong, Y. Wang, X. Zhang, S. Zhu, Y. T. Chow, X. Wang, L. Zhu, G. Zhang, D. Xu (2021) Self-supporting super hydrophilic MgFe2O4 flexible fibers for Pb (II) adsorption. Separation and Purification Technology, 266, 118584
[92] W. Ahmed, S. Mehmood, A. N. Delgado, S. Ali, M. Qaswar, A. Shakoor, M. Mahmood, D. Y. Chen (2021) Enhanced adsorption of aqueous Pb (II) by modified biochar produced through pyrolysis of watermelon seeds. Science of the Total Environment, 784, 147136
[93] C. Q. Teong, H. D. Setiabudi, N. A. S. E. Arish, M. B. Bahari, L. P. The (2021) Vatica rassak wood waste-derived activated carbon for effective Pb (II) adsorption: Kinetic, isotherm and reusability studies. Materials Today: Proceedings, 42, 165-171
[94] L. Wang, L. Yanga, Y. Li, Y. Zhanga, X. Ma, Z. Ye (2010) Study on adsorption mechanism of Pb (II) and Cu (II) in aqueous solution using PS-EDTA resin. Journal Chemical Engineering, 163, 364-372
[95] A. Hashem, C.O. Aniagor, G. M. Taha, M. Fikry (2021) Utilization of low-cost sugarcane waste for the adsorption of aqueous Pb (II): Kinetics and isotherm studies. Current Research in Green and Sustainable Chemistry, 4, 100056
[96] H. Xu, X. Hu, Y. Chen, Y. Li, R. Zhang, C. Tang, X. Hu (2021) Cd (II) and Pb (II) absorbed on humic acid-iron-pillared bentonite: Kinetics, thermodynamics and mechanism of adsorption. Colloids and Surfaces A: Physicochemical and Engineering Aspects, 612(5), 126005
[97] R. Zaidi, S. U. Khan, I. H. Farooqi, A. Azam (2021) Rapid adsorption of Pb (II) and Cr (VI) from aqueous solution by Aluminum hydroxide nanoparticles: Equilibrium and kinetic evaluation. Materials Today: Proceedings, 44(7)
[98] N. Rahman, M. Nasir, P. Varshney, A. M. Al-Enizi, M. Ubaidullah, S. F. Shaikh, M. A. Al-Adrabalnabi (2021) Efficient removal of Pb (II) from water using silica gel functionalized with thiosalicylic acid: Response surface methodology for optimization. Journal of King Saud University – Science, 33(1),101232
[99] M. J. S. Aguilar, A. M. Lue´vanos, M. A. S. Castillo, F. R. C. Pedroza, N. Toro, V. M. N. Garcıa (2021) Removal of Pb (II) from aqueous solutions by using steelmaking industry wastes: Effect of blast furnace dust’s chemical composition. Arabian Journal of Chemistry, 14(4), 103061
[100] Z. Ma, R. Xue, J. Li, Y. Z., Q. Xue, Z. Chen, Q. Wang, C. S. Poon (2021) Use of thermally modified waste concrete powder for removal of Pb (II) from wastewater: Effects and mechanism. Environmental Pollution, 277, 116776
[101] R. Cheng, M. Kang, S. Zhuang, L. Shi, X. Zhenga, J. Wang (2019) Adsorption of Sr (II) from water by mercerized bacterial cellulose membrane modified with EDTA. Journal of Hazardous Materials, 364, 645-653
[102] J. Ryu, S. Kim, H.J. Hong, J. Hong, M. Kim, T. Ryu, I.S. Park, K.S. Chung, J.S. Jang, B.G. Kim (2016) Strontium ion (Sr2+) separation from seawater by hydrothermally structured titanate nanotubes: Removal vs. recovery. Journal Chemical Engineering, 304, 503-510
[103] L. Zhang, J. Wei, X. Zhao, F. Li, F. Jiang, M. Zhang, X. Cheng (2016) Competitive adsorption of strontium and cobalt onto tin antimonate. Journal Chemical Engineering, 285, 679-689
[104] M. Ghaly, F.M.S.E..E Dars, M.M. Hegazy, R.O. A. Rahman (2016) Evaluation of synthetic Birnessite utilization as a sorbent for cobalt and strontium removal from aqueous solution. Journal Chemical Engineering, 284, 1373-1385
[105] J. Liang, J. Li, X. Li, K. Liu, L. Wu, G. Shan (2020) The sorption behavior of CHA-type zeolite for removing radioactive strontium from aqueous solutions. Separation and Purification Technology, 230, 115874
[106] Y. Li, A.O. Simon, C. Jiao, M. Zhang, W. Yan, H. Rao, J. Liu, J. Zhang (2020) Rapid removal of Sr2+, Cs+ and UO2+ from solution with surfactant and amino acid modified zeolite Y. Microporous and Mesoporous Materials, 302, 110244
[107] S. Wang, S. Ning, W. Zhang, S. Zhang, J. Zhou, X. Wang, Y. Wei (2020) Synthesis of carboxyl group functionalized silica composite resin for strontium removal. Materials and Design, 185, 108224