壳聚糖-富里酸协同调控Ca_xCd_(1-x)CO_3固溶体结晶

Study on the Synergistic Regulation of Ca_xCd_(1-x)CO_3 by Chitosan-Fulvic Acid

以壳聚糖和富里酸混合溶液为介质,利用碳酸铵气相扩散法合成Ca_xCd_(1-x)CO_3固溶体,文章研究了Ca_xCd_(1-x)CO_3固溶体成核结晶行为,探究这2种介质对于Ca_xCd_(1-x)CO_3固溶体固化Cd能力及稳定性的影响。通过结晶固相成分分析,结果表明液相中各组分浓度能够影响固相中Cd的含量。液相Cd^(2+)浓度增加,Cd在固溶体中的含量也增加。随着富里酸浓度增加,固溶体中Cd含量降低,意味着在富里酸存在下固溶体固化Cd能力降低。红外光谱和XRD结果证明了壳聚糖和富里酸不影响固溶体晶体的结构。扫描电镜和透射电镜分析进一步表明,壳聚糖和富里酸在不同程度上都影响了固溶体的晶体形貌及固相组成。在壳聚糖存在下晶体表面形成薄膜将晶体包覆,随着壳聚糖浓度增加,固溶体中Cd含量增加到39.90%,且晶体形貌逐渐转向球体。该研究结果表明Cd^(2+)进入碳酸钙晶格中能有效降低溶液中的Cd^(2+)达到净化水体的效果,壳聚糖和富里酸的协同作用实现了水体中重金属Cd^(2+)的转化和钝化。

CaxCd1-xCO3 solid solution was synthesized in the mixed media of chitosan and fulvic acid by the ammonium carbonate gaseous diffusion method. Further, effects of two media for some aspects of CaxCd1-xCO3 solid solution including its nucleation behavior, solidifying Cd ability and stability were investigated. The results of composition analysis in solid phase show that Cd contents in solid phase can be relative with the composition in aqueous phase. The higher the Cd concentration is in aqueous phase, the higher the Cd content is in solid phase. However, with the increasing concentration of fulvic acid,Cd content in solid phase is decreasing, indicating that the solidifying Cd ability of solid solution becomes weak in acidic conditions. The results of FTIR and XRD confirm that the structure of CaxCd1-xCO3 solid solution is not affected by chitosan and fulvic acid. However, its morphology and composition have a large relationship with these two media. These are confirmed by analysis of SEM and TEM. The chitosan can form thin film to clad crystal. With the increasing concentration of chitosan,Cd content in CaxCd1-xCO3 solid solution adds up to 39.90% and the morphology of solid solution gradually changes into sphere. The studied results display that Ca2+in the calcium carbonate crystal can be replaced by Cd2+ so that decreasing the Cd2+ content could realize the aim of purifying water body. The synergistic effect of chitosan and fulvic acid achieve the conversion and passivation of heavy metal Cd2+ in water body, which is significant for the environmental governance of cadmium.