Fe/La定向修饰凹凸棒土稻壳基颗粒成型生物炭:磷酸盐吸附行为与机制

A formable biochar made from rice hull and attapulgite particles modificated by Fe/La:Phosphate adsorption behavior and mechanism

本研究合成一种新型除磷载Fe/La定向修饰凹凸棒土稻壳基颗粒成型生物炭吸附材料(Fe-La/AC),考察了材料表面特性、Fe/La投加量、热解温度、保温时间以及凹凸棒土投加量等对磷素吸附影响规律.Fe/La最佳投加量为2:2 mmol,AT添加量为30%,热解温度为350℃,热解时间2 h,制备的Fe-La/AC对磷酸根的最大吸附量可以达到47.62 mg·g^(-1)(以磷计).傅里叶红外光谱分析表明Fe、La主要以铁镧氧化物及铁镧水合氯化物的形式存在于炭材料表面,Fe和La提供了磷酸盐吸附的活性中心.该材料吸附动力学过程符合准二级动力学模型,吸附等温线拟合分析Langmiur模型更适于描述Fe-La/AC对磷酸盐的吸附过程,表明吸附动力学主要受化学作用控制.磷酸盐吸附机制主要涉及静电吸引、配体交换和内层络合作用.本研究制备的Fe-La/AC颗粒成型生物炭,可作为低磷浓度废水处理及水体富营养化调控的一种高效除磷吸附剂,具有较大的实际应用前景.

A novel Fe/La-loaded rice hull and attapulgite(AT)particles composite formable biochar adsorption material(Fe-La/AC)for phosphorus removal was synthesized in this study.The effects of surface characterization of this material,Fe/La dosage,pyrolysis temperature,holding time,and attapulgite dosage on phosphorus removal were studied.The maximum adsorption capacity of Fe-La/AC prepared on phosphate reached 47.62 mg·g^(-1)(calculated in P)when the optimum dosage of Fe/La was 2∶2 mmol(AT/RHC moles),AT dosage was 30%(RHC),pyrolysis temperature was 350℃,and pyrolysis time was 2 h.Fourier transform infrared spectroscopy(FTIR)analysis results showed that Fe and La existed mainly in the form of Fe lanthanum oxide and Fe/La-Si-O on the surface of biochar,and Fe/La provided the active center of phosphate adsorption.The adsorption kinetics follows pseudo-first/second order model and the adsorption of Fe-La/AC to phosphate is well fitted by Langmiur adsorption isotherm model.It is suggested that adsorption kinetics is mainly controlled by chemical action.The adsorption mechanism of phosphate mainly involves the electrostatic attraction,ligand exchange,and inner-sphere complexation.The Fe-La/AC particle formable biochar prepared in this study can be used as efficient phosphorus removal adsorbent in wastewater treatment with low phosphorus and the control of eutrophication,which has a great application prospect.