结垢对电吸附除盐的影响及其控制

Effect of Scaling on Electrosorption Desalination and Its Control

利用电吸附技术对含有高重碳酸盐(HCO3-)和不同浓度Ca2+的原水进行除盐处理,研究了结垢对电吸附除盐的影响.实验分别在Ca2+浓度为40,144和350mg/L三种工况下进行,结果表明,当Ca2+浓度较高时,除盐率明显下降.对离子去除率、离子脱附率和起始工作电流的变化进行了分析,认为Ca2+与HCO3-相互作用在电吸附模块内部形成碳酸钙垢体,导致电极的双电层电容量降低,从而影响电吸附的除盐效果.利用酸化吹脱预处理将原水中HCO3-浓度控制在100mg/L,可使碳酸钙垢体溶解,改善模块的除盐性能.根据HCO3-积存和工作出水pH值的变化,探讨了碳酸钙在模块内部的结晶与溶解机理.

The effect of scaling on electrosorption desalination was studied by using electrosorption technology to desalt feed water containing different concentrations of Ca^2＋ and high concentration bicarbonate （HCO3^-）. The experiments were carried out at three Ca^2＋ concentrations of 40, 144 and 350 mg/L, respectively. The results show that the desalination efficiency drops remarkably at higher Ca^2＋ concentrations. Analysis of changes of ion removal rate, ion desorption rate and initial working current reveals that the calcium carbonate scale formed in the electrosorption module is a result of the interaction between Ca^2＋ and HCO3^-, which causes the decrease of electrical double layer capacitance of electrode material, and therefore affects the desalination effect. Calcium carbonate can be dissolved after using acidification-stripping as pretreatment to obtain HCO3^- concentration of 100mg/L, which results in the improvement of desalination of the module. The crystallization and dissolution mechanism of calcium carbonate in the module are also discussed based on HCO3^- ion residue and pH change in the working effluent.