| 研究実績の概要 |
The approach to search a single-adsorbent for both AsO33- and F- removal is based on application of the hard-soft acids base (HSAB) concept, and also on exploring the suitability of sucrose derived porous carbon (PSC). Amorphous ZrOOH, LaOOH, ZrxLa1-xOOH and ZrxLa1-xOOH prepared by chemical co-precipitation were homogeneously dispersed into PSC. The ZrxLa1-xOOH and PSC-ZrxLa1-xOOH composite materials showed both fast adsorption rates and high adsorption capacities towards AsO33- and F- in aqueous solution. ZrxLa1-xOOH and PSC-ZrxLa1-xOOH showed better F- adsorption capacity at pH < 7, better AsO33- removal at pH > 9 and were superior to previously reported metallic oxide-based sorbents. The mechanism can be interpreted based on the HSAB principle, where the bimetallic oxyhydroxides become SA, while La3+ and Zr4+ are categorized as HA. Moreover, the PSC-ZrxLa1-xOOH adsorbent demonstrated high selectivity for AsO33- in the co-existence of other ions in a triple component system. Also, biopolymer, chitosan (CS) is an aqueous-stable biopolymer derived from insect and shellfish exoskeletons and it possesses surface rich in -OH and -NH2 groups, useful for bonding transition metal ions through chelation which helps to enhance the adsorption capacity of several toxic ions. Chemical precipitation method was employed to synthesize ZrOOH, AlOOH, ZrxAl1-xOOH and CS@ ZrxAl1-xOOH and tested for simultaneous removal of AsO33- and F-. The CS@ZrxAl1-xOOH adsorbent may form borderline character, and this may be responsible for adsorption of AsO33- and F- through HSAB principle.
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