柠檬酸对制革废水中三价铬沉淀性能影响研究

Precipitation effect of citric acid on trivalent chromium in tanning wastewater

选取制革常用有机酸柠檬酸（CA）与Cr3＋形成络合液，CA-Cr，对CA-Cr的耐碱性进行研究，采用高效毛细管电泳法（HPCE）、凝胶渗透色谱法（GPC）和能谱仪（EDS），分则对CA-Cr的络合液和碱沉淀物进行袁征。研究结果表明：CA-Cr络合体系中Cr3＋的耐碱性较好，可以在pH值为4～11区间内稳定存在，CA的加入对Cr（OH），沉淀物生成亚铬酸根离子（CrO2＋）有抑制作用。当pH=8时，不同配比的CA-Cr络合液，CA浓度越高，Cr3＋的耐碱性越好，且随着CA浓度的增加CA-Cr的稳定性增强；CA与Cr3＋形成配位体，对Cr3＋和CA之间的移动产生限制作用；CA与Cr3＋发生了共沉淀；CA-Cr的分子质量要明显大于单独CA和Cr3＋的分子质量，说明CA与Cr3＋发生络合作用。

Alkali resistance of complex fluid CA - Cr was investigated, which was prepared by citric aid （CA） commonly used in tanning and Cr3 ＋. Complex fluid and alkali precipitate of CA - Cr were characterized by high - performance capillary elec- trophoresis （HPCE） , gel permeation chromatography （GPC） and energy dispersive spectrometer （ EDS. ） The results show that al- kali resistance of Cr3 ~ is better in CA - Cr complexation system and it is stable when the pH is between 4 - 11. CrO2- iron genera- ting from precipitation of Cr（OH） 3 is inhibited by the adding of CA. When pH is 8, the higher of CA concentration, the better the alkali precipitate of Cr3＋ is with different proportions of CA - Cr complex fluid. And the stability of CA - Cr is enhanced with increased concentration of CA. Movement between Cr3＋ and CA is limited by the formation of ligand between CA and Cr3 ＋. Co - precipitation between CA and Cr3 ＋ is formed. Molecular weight of CA - Cr is significantly greater than that of individual molecular weight of CA and Cr3＋ because of compiexation.