MgCO3净化含铬废水的溶液化学

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 -3 3 .50 )小于在溶液中的溶度积 (KSP=10 -3 0 .2 7) ,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 .

Solution chemistry of purifying chromium ion wastewater with MgCO3

The pH scope for neutralization sedimentation of chromium ion is comparatively narrow ( 6.3～9.5) and thedosage must be controlled strictly when NaOH or CaO was used. A little dissolution of MgCO3 makes it possible that thesolution has buffer pH (pH = 8.4)which accord with the condition of neutralization sedimentation of chromium ion. It iseasier to form hydroxide sediment for Cr3+ in interface area than in solution because the interracial solubility product ofCr(OH)3 formed on the surface of MgCO3 is less than the solubility productin solution (KSP S = 10-33.50 and KSP =10-30.27). After surface sediment is formed, the dynamic electricity behavior of MgCO3 is similar to Ct(OH)3. Usingmagnesite as purifier, the waste water with high concentration of chromium ion is purified, and some advantages, such asgood purifying effect, fast subside speed and little sediment volume are manifested.