镧生物质炭对磷酸根离子的吸附特性

摘要

As a kind of high⁃effect, low⁃cost, environment⁃friendly and recyclable PO4 3- adsorbent intended for use in farmlands, La⁃containing cornstalk based biochar was prepared for the first time for analysis of phosphate adsorption char⁃acteristics with thermodynamic, isothermic and kinetic methods. During the adsorption process,its Gibbs free energy de⁃clined below zero, while enthalpy and entropy both rose above zero. Its adsorption isotherm fitted the Langmuir model and its adsorption peaked up to 78�36 mg·g-1 at 25℃. Its kinetics fitted the pseudo⁃second⁃order kinetic model with its ad⁃sorption rate constant being 23�19×10-2 mg·g-1·min-1 when the initial phosphate concentration was 50 mg·L-1. The straightline fitted with the intra⁃particle diffusion model failed to pass the origin of the coordinates, but was displayed in a two⁃section line. When soil pH lingered in the range of 3-7, its phosphate adsorption capacity was quite high and not af⁃fected by any of the coexisting ions, except 200 mg·L-1 of CO3 2- and 2 000 mg·L-1 of CO3 2-and F-. Its phosphate ad⁃sorption was a kind of spontaneous endothermic reaction, and physical adsorption dominated monolayer adsorption. Its ad⁃sorption process was governed mainly by surface diffusion and intra⁃particle diffusion and its adsorption rate by thickness of the boundary layer. The La⁃containing cornstalk⁃based biochar is extensively applicable to farmlands with pH in a wide range, quite strong in disturbance resisting ability and quite high in phosphate adsorption and adsorption rate. The La⁃con⁃taining cornstalk⁃based biochar enjoys a broad application prospect in the future in remedying eutrophied bodies and purif⁃ying phosphorus⁃polluted wastewater.%针对首次合成的高效、低成本、环境友好并可回收还田再利用的镧玉米秸秆炭磷酸根离子（ PO43－）吸附剂，采用热力学、等温线和动力学等吸附试验方法，研究了镧玉米秸秆炭对PO43－的吸附特性。在镧玉米秸秆炭吸附PO43－过程中，自由能变小于0，而焓变和熵变大于0；等温线符合Langmuir等温吸附模型，25℃时最大吸附量为78�36 mg·g－1；动力学符合准二级动力学模型，PO43－初始质量浓度为50 mg·L－1时的吸附速率常数为23�19×10－2 mg·g－1·min－1；颗粒内扩散模型拟合直线不通过坐标原点而表现为二段线性；吸附量在pH值为3～7范围内较大，且不受除200 mg·L－1 CO32－与2000 mg·L－1 CO32－和F－外其余共存离子的影响。镧玉米秸秆炭对PO43－的吸附是自发的吸热反应，是以物理吸附为主的单层吸附；吸附过程由表层扩散和颗粒内扩散主导，吸附速率由边界层厚度控制；镧玉米秸秆炭对PO43－的吸附具有较广的pH应用范围、较强的抗干扰能力以及较大的吸附量和吸附速率。镧玉米秸秆炭在富养化水体和含磷废水的净化中具有广阔的应用前景。