铁基膨润土对水中磷酸根的吸附热力学及动力学研究

Study on kinetics and thermodynamics for phosphate in aqueous solution adsorption onto iron-modified bentonite

采用铁盐改性制得铁基膨润土,研究了其对水中磷酸根的吸附性能及影响因素,结果表明,通过对膨润土的改性提高了磷的去除率,含磷废水初始pH值的大小对磷的去除率影响不大,初始浓度越低越有利于磷的去除。磷的去除率随改性膨润土的投加量增大而提高,随温度升高而增大。进一步研究表明,改性膨润土对磷的吸附是吸热反应,其吸附等温线可采用Langmuir等温吸附方程拟合;改性膨润土对磷的吸附是快速吸附,在20 min内,磷去除率达70%以上,符合准二级吸附动力学模型。

A modified bentonite was successfully prepared by reaction of nature bentonite with ferric salt.Its efficiency as an adsorbent for phosphate removal from aqueous solutions was evaluated by batch adsorption experiments and compared with that of unmodified bentonite.The studies showed that phosphate-uptake capacity of modified bentonite was significantly improved and over 70% of phosphate could be removed from water within 20 min.The effects of initial pH value,phosphate concentration,adsorbent dosage and temperature on the phosphate removal rate and capacity were systematically studied.The results indicated that low phosphate concentration,large adsorbent dosage and high temperature favored the removal of phosphate,while the initial pH value of the phosphate solution has little effect.The removal of phosphate originated from the phosphate adsorption on modified bentonite,which was an endothermal process and the adsorption isotherm fitted with Langmuir equation.In addition,adsorption kinetics showed that the adsorption of phosphate on modified bentonite was a fast adsorption process which could be well described by a pseudo-second-order model.