铁盐除砷中水化作用的微观研究

Microscopic Study on Hydration in Arsenic Removal by Iron Salt

摘要: 水溶液中砷的除去与水化作用密切相关。本文借助量子化学方法分析了铁盐除砷时砷酸盐周围水化特征的情况。对于[H_mAsO₄(H₂O)_n]^3−m (m = 0~2)水合团簇，随着氢质子化，[H_mAsO₄(H₂O)_n]^3−m的水化减弱，O_N-H_W距离小于O_P-H_W，而O_N-H_W配位数大于O_P-H_W。Fe³⁺与H_mAsO₄^m−3缔合改变了H_mAsO₄^m−3水化情况。相对于[H_mAsO₄]^3−m (m = 0~2)物种，[FeH_mAsO₄]^m+ (m = 0~2)缔合团簇中[H_mAsO₄]^3−m的水化能力降低，从而达到沉淀除砷。[FeH_mAsO₄]^m+ (m = 0~2)缔合团簇的水化则随着质子化，[FeH_mAsO₄]^m+ (m = 0~2)的水化增强。

Abstract: The removal of arsenic from aqueous solution is closely related to hydration. In this paper, the hydration characteristics around arsenate during arsenic removal from iron salt were analyzed by means of quantum chemistry. For the hydrating cluster of [H_mAsO₄(H₂O)_n]^3−m (m = 0~2), the hydration of [H_mAsO₄(H₂O)_n]^3−m decreases with hydrogen protonation, and the O_N-H_W distance is less than the O_P-H_W, while the O_N-H_W coordination number is greater than the O_P-H_W. The association of Fe³⁺ with H_mAsO₄^m−3 changed the hydration of H_mAsO₄^m−3. Compared with [H_mAsO₄]^3−m (m = 0~2) species, the hydration capacity of [H_mAsO₄]^3−m in [FeH_mAsO₄]^m+ (m = 0~2) association cluster was reduced, so as to achieve precipitation and arsenic removal. The hydration of [FeH_mAsO₄]^m+ (m = 0~2) association clusters was enhanced with the protonation of [FeH_mAsO₄]^m+ (m = 0~2).