Co-removal of Hexavalent Chromium through Copper Precipitation in Synthetic Wastewater

详细信息    查看全文

• 作者：Jing-Mei Sun ; Chii Shang ; and Ju-Chang Huang
• 刊名：Environmental Science & Technology
• 出版年：2003
• 出版时间：September 15, 2003
• 年：2003
• 卷：37
• 期：18
• 页码：4281 - 4287
• 全文大小：252K
• 年卷期：v.37,no.18(September 15, 2003)
• ISSN：1520-5851

文摘

The mechanisms of hexavalent chromium [Cr(VI)] co-removal with copper [Cu(II)] during homogeneous precipitationwere studied with batch tests using a synthetic solutioncontaining Cr(VI) and Cu(II). Metal precipitation was inducedby adding Na₂CO₃ stepwise to different pH, and therespective removals of Cu(II) and Cr(VI) were measured.At the same time, the relative quantities of Cu(II) andCr(VI) in the precipitates were also analyzed to establishtheir stoichiometric relationship. The results indicated that,in a solution containing 150 mg/L Cu(II) and 60 mg/LCr(VI), the initial co-removal of Cr(VI) with Cu(II) began atpH 5.0 and completed at pH 6.2. At pH 5.0-5.2, coprecipitation took place through the formation of copper-chromium-bearing solids [such as CuCrO₄ and/or CuCrO₄·2Cu(OH)₂]. Thereafter, the remaining soluble copperstarted to react with carbonate in a heterogeneousenvironment to form the negatively charged basic coppercarbonate precipitates [CuCO₃·Cu(OH)₂], which subsequently adsorbed additional Cr(VI) (or HCrO₄^-) at pH5.2-6.2. The maximum Cr(VI) co-removal took place at pH6.2. Between the two mechanisms, coprecipitationaccounted for about 29% of the total chromium's co-removal while the remaining 71% was attributed to surfaceadsorption, mainly through electrostatic attraction andligand exchange. When the solution pH was increased tobeyond 7.5, a surface charge reversal took place on thebasic copper carbonate solids, and this led to someCr(VI) desorption. Thus, the extent of Cr(VI) adsorption ishighly pH dependent.