载镧磁性水热生物炭的制备及其除磷性能

Fabrication of La-MHTC Composites for Phosphate Removal: Adsorption Behavior and Mechanism

将小麦秸秆在水热条件下(220℃)炭化2 h得到水热生物炭(HTC),以HTC为载体,通过一步共沉淀法制备了一种吸附容量高、易于磁分离回收的载镧磁性水热生物炭复合材料(La-MHTC).通过等温线和动力学等吸附实验方法,研究了该材料对磷酸根的吸附特性,考察了载镧量、初始pH和共存离子等因素对磷酸根吸附过程的影响.结果表明La3+∶Fe3+为2∶1时,材料(2-La-MHTC)具有良好的吸附磷酸根的能力;在吸附剂投加量为0.1 g·L^-1,pH为7时,对磷酸盐吸附量达到100.25mg·g^-1;吸附符合Langmuir等温模型,吸附动力学过程遵循准二级动力学,并且吸附不受其它离子的影响(在Cl^-、NO3^-和SO4^2-等共存离子体系磷酸盐去除率达到98%),在较广的pH(3~10)范围都具有良好的吸磷能力.吸附的磷酸根可用NaOH溶液解吸,5次吸附-脱附循环实验中磷酸盐去除率均能达到90%以上,脱附效率为65%左右,说明该吸附剂具有良好的脱附和重复利用能力.应用其处理实际含磷污水,可将磷酸盐浓度从0.87 mg·L^-1降低到0.05 mg·L^-1.吸附机制主要为静电吸附作用和La(OH)3与磷酸盐通过配体交换形成内层络合物.

Lanthanum(La)-based materials have shown great potential for phosphate removal owing to the strong affinity between La and phosphate.In this study,magnetic hydrothermal biochar immobilized La(OH)3(La-MHTC)were prepared and used as phosphate adsorbents.Hydrochar was produced by the hydrothermal carbonization process(220℃,2 h).Magnetic La-MHTC with different Lato-Fe mass ratios were synthesized by the co-precipitation method.Subsequently,La-MHTC was applied to remove phosphate from wastewater.Results indicate that La-MHTC(with a La-to-Fe mass ratio of 2∶1)exhibited excellent magnetic properties for easy recovery and high phosphate adsorption capacity up to 100.25 mg·g^-1.Effective phosphate removal was obtained over a wide pH range of 3-10.The absorption isotherm and kinetics were better fitted by the Langmuir model and the pseudo second-order model,respectively,which showed a fast adsorption rate and exhibited superior La utilization efficiency.The La-MHTC has strong selectivity for phosphate in the presence of coexisting ions(Cl^-,NO3^-,and SO4^2-).The adsorption-desorption experiment suggested its excellent stability and cyclic utilization.In addition,La-MHTC was applied to treat real domestic wastewater,efficiently reducing the phosphate concentration(from 0.87 mg·L^-1 to 0.05 mg·L^-1).Electrostatic attraction and inner-sphere complexation between La(OH)3 and P via ligand exchange were the main mechanisms of phosphate adsorption by La-MHTC.