MgCO₃净化含铬废水的溶液化学

来源期刊：中南大学学报(自然科学版)2000年第5期

论文作者：王晖

文章页码：429 - 432

关键词：MgCO₃;废水处理;铬离子;溶液化学

Key words：MgCO₃; wastewater treatment; chromium ion; solution chemistry

摘    要：中和沉淀Cr³⁺的pH范围较窄(6.3~9.5)决定了采用NaOH或CaO时投药量必须严格控制.MgCO₃在溶液中的少量溶解导致体系具备pH缓冲性质,且该缓冲pH值(pH=8.4)能够满足中和沉淀Cr³⁺的条件;Cr³⁺在MgCO₃表面生成Cr(OH) ₃沉淀的界面溶度积(KSSP=10-33.50)小于在溶液中的溶度积(K^S_SP=10-30.27),Cr³⁺在界面区域比在溶液中更易形成氢氧化物沉淀;表面沉淀生成之后,MgCO₃表现出类似Cr(OH) ₃的动电行为.采用含MgCO₃矿物菱镁石为净化剂,在较低用量下能够净化极高浓度含铬废水,不仅净化效果好而且具有沉降速度快、污泥体积小等优点.

Abstract: The pH scope for neutralization sedimentation of chromium ion is comparatively narrow (6.3~9.5) and the dosage must be controlled strictly when NaOH or CaO was used. A little dissolution of MgCO₃ makes it possible that the solution has buffer pH (pH=8.4)which accord with the condition of neutralization sedimentation of chromium ion. It is easier to form hydroxide sediment for Cr³⁺ in interface area than in solution because the interfacial solubility product of Cr(OH) ₃ formed on the surface of MgCO₃ is less than the solubility product in solution (K^S_SP=10-33.50andKSP=10-30.27). After surface sediment is formed, the dynamic electricity behavior of MgCO₃ is similar to Cr(OH)₃. Using magnesite as purifier, the waste water with high concentration of chromium ion is purified, and some advantages, such as good purifying effect, fast subside speed and little sediment volume are manifested.