Adsorption of single and mixed haloacetonitriles on silica-based porous materials: Mechanisms and effects of porous structures |
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| Authors: | Panida Prarat Chawalit Ngamcharussrivichai Sutha Khaodhiar and Patiparn Punyapalakul |
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| Institution: | International Postgraduate Programs in Hazardous Substance and Environmental Management, Graduate School, Chulalongkorn University, Bangkok 10330, Thailand;Center of Excellence on Hazardous Substance Management (HSM), Chulalongkorn University, Bangkok 10330, Thailand,Department of Chemical Technology, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand;The Center of Excellence on Petrochemical and Materials Technology (PETROMAT), Chulalongkorn University, Bangkok 10330, Thailand,Department of Environmental Engineering, Faculty of Engineering, Chulalongkorn University, Bangkok 10330, Thailand and Center of Excellence on Hazardous Substance Management (HSM), Chulalongkorn University, Bangkok 10330, Thailand;Department of Environmental Engineering, Faculty of Engineering, Chulalongkorn University, Bangkok 10330, Thailand;Research unit Control of Emerging Micropollutants in Environment, Chulalongkorn University, Bangkok 10330, Thailand;Research Network of NANOTEC - CU on Environment, Bangkok 10330, Thailand |
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| Abstract: | Adsorption mechanisms and the role of different porous and crystalline structures on the removal of five haloacetonitriles(HANs) over hexagonal mesoporous silica(HMS), titanium substituted mesoporous silica(Ti-HMS), rod-shaped SBA-15 and microporous zeolite Na Y were investigated. In addition, the effect of p H on adsorption mechanism and selective adsorption of five HANs individually and in an equimolar mixed solution were evaluated.The results indicated that the intraparticle diffusion rate constants of the mesoporous adsorbents were higher than that of the microporous Na Y. In single solute, the order of adsorption preference(highest to lowest) was mono-HANs di-HANs tri-HAN. However,in mixed solute, the large molecular weight of the tri-HAN and di-HANs are more easily adsorbed than the smaller molecular weight mono-HANs. Except for SBA-15, the order of adsorption capacities in mixed HANs solute was not different compared to that observed for the single HAN solute, which might be caused by the higher accessibility to the active sites due to larger pore size. The ion-dipole electrostatic interaction was likely to be the main adsorption mechanism, and was favored at high p H values due to the high negative surface charge density of the adsorbent. The molecular structure of the HANs and hydrophilic/hydrophobic nature affected the adsorption capacities and their selective adsorption from mixed solutes. |
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| Keywords: | Haloacetonitrile Adsorption mechanism Porous structure Ion-dipole electrostatic interaction Hydrophilicity |
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