球磨法制备铁改性生物炭吸附水溶液中磷酸盐研究

Fe_(2)O_(3) impregnated biochar produced via ball milling for enhanced phosphate adsorption in aqueous solution

采用吸附法降低水体中磷酸盐浓度是目前治理和控制水体富营养化的常见手段之一.生物炭(BC)作为一种廉价的化学稳定型吸附材料,尤其适用于对阳离子型污染物的吸附与去除,但生物炭表面负电性和有限的吸附位点限制了其对磷酸盐的吸附性能.本研究使用球磨法将氧化铁负载于玉米秸秆生物炭得到一种具备高效除磷性能的复合材料.使用X射线衍射光谱仪、扫描电子显微镜、氮气吸附-解吸、傅里叶红外光谱仪、X射线电子能谱、Zeta电位仪对复合材料进行了表征检测,采用系列批次实验考察了材料对水溶液中正磷酸盐(PO_(4)^(3-))的吸附性能和吸附机制.结果表明,球磨处理成功将氧化铁(Fe_(2)O_(3))负载至生物炭表面,极大地提高了生物炭比表面积(210 m^(2)·g^(-1))、Zeta电势和含氧官能团种类和数量.溶液初始pH和吸附剂投加量是影响磷酸盐去除率的关键因素.Langmuir方程能更好地拟合等温吸附过程:当溶液pH=5.0,投加量为2.0 g·L^(-1)时,制备的球磨氧化铁改性生物炭达到对磷酸盐的理论最大吸附量(45.03 mg·g^(-1)).吸附动力学过程更加符合假二级动力学方程,表明化学过程主导整个吸附过程.共存离子(Cl^(-)、NO_(3)^(-)和SO_(4)^(2-))对磷酸盐吸附性能的影响可忽略不计.连续6次的吸附-解吸实验结果说明球磨氧化铁负载生物炭具备较好的化学稳定性和可循环使用性.系列表征分析结果显示:主要的吸附机制包括表面络合、金属-磷桥接和配位吸附.本研究为水体中磷素控制提供了一种可行策略,也为高效吸附材料的制备提供了新的思路.

The adsorption method was still considered as one of the common strategies to control the eutrophication by reducing the phosphate(P)concentration.Biochar(BC),a low-cost adsorbent with good chemical stability,was particularly used to remove the cationic pollutant.However,its negatively charged surface and limited adsorption site greatly retarded the adsorption capacity on P.In this study,a Fe_(2)O_(3) impregnated corn stalk biochar(BM-Fe-BC) with excellent P removal efficiency was obtained using a facile ball milling method.The physicochemical properties,adsorption performance,and mechanism of as-prepared BM-Fe-BC for P in aqueous solution were investigated by a series of characterization techniques(i.e.Xray diffractometer,scanning electron microscopy,N_(2) adsorption-desorption,Fourier transform infrared spectrometer,X-ray photoelectron spectroscopy,and Zeta potentiometer) and batch experiment.Results showed that ball milling successfully impregnated Fe_(2)O_(3) within the framework of pristine BC,significantly changing the specific surface area(from 7.89 m^(2)·g^(-1) to 210 m^(2)·g^(-1)),Zeta potential(from-9.17 mV to 0.96 mV),and enriching the oxygen-containing functional groups.The initial solution pH and adsorbent dosage were key factors affecting the P removal efficiency.Langmuir model could well describe the adsorption isotherm and the theoretical maximum adsorption capacity of BM-Fe-BC(45.03 mg·g^(-1)) was achieved when the solution pH was 5.0 and dosage reached 2.0 g·L^(-1).The pseudo-second-order model correlated satisfactorily with the adsorption kinetics,revealing that the chemical process dominated the entire adsorption process.Additionally,the adsorption capacity was negligibly influenced by the co-existing anions(Cl^(-),NO_(3)^(-) and SO_(4)^(2-)).A consecutive six runs of adsorption-desorption experiment suggested its excellent chemical stability and recyclability.Solid state analysis of the BM-Fe-BC before and after adsorption indicated that the predominant adsorption mechanism may include surface complexation,metal-phosphorus bridging,and coordination adsorption.This study provided a green and sustainable strategy for the P control in The adsorption method was still considered as one of the common strategies to control the eutrophication by reducing the phosphate(P) concentration.Biochar(BC),a low-cost adsorbent with good chemical stability,was particularly used to remove the cationic pollutant.However,its negatively charged surface and limited adsorption site greatly retarded the adsorption capacity on P.In this study,a Fe_(2)O_(3) impregnated corn stalk biochar(BM-Fe-BC) with excellent P removal efficiency was obtained using a facile ball milling method.The physicochemical properties,adsorption performance,and mechanism of as-prepared BM-Fe-BC for P in aqueous solution were investigated by a series of characterization techniques(i.e.Xray diffractometer,scanning electron microscopy,N_(2) adsorption-desorption,Fourier transform infrared spectrometer,X-ray photoelectron spectroscopy,and Zeta potentiometer) and batch experiment.Results showed that ball milling successfully impregnated Fe_(2)O_(3) within the framework of pristine BC,significantly changing the specific surface area(from 7.89 m^(2)·g^(-1) to 210 m^(2)·g^(-1)),Zeta potential(from-9.17 mV to 0.96 mV),and enriching the oxygen-containing functional groups.The initial solution pH and adsorbent dosage were key factors affecting the P removal efficiency.Langmuir model could well describe the adsorption isotherm and the theoretical maximum adsorption capacity of BM-Fe-BC(45.03 mg · g^(-1)) was achieved when the solution pH was 5.0 and dosage reached 2.0 g · L^(-1).The pseudo-second-order model correlated satisfactorily with the adsorption kinetics,revealing that the chemical process dominated the entire adsorption process.Additionally,the adsorption capacity was negligibly influenced by the co-existing anions(Cl^(-),NO_(3)^(-) and SO_(4)^(2-)).A consecutive six runs of adsorption-desorption experiment suggested its excellent chemical stability and recyclability.Solid state analysis of the BM-Fe-BC before and after adsorption indicated that the predominant adsorption mechanism may include surface complexation,metal-phosphorus bridging,and coordination adsorption.This study provided a green and sustainable strategy for the P control in water bodies,and also offered a new insight into the development of high-performance biochar-based adsorbent.