KOH活化小麦秸秆生物炭对废水中四环素的高效去除

Effect of KOH Activation on the Properties of Biochar and Its Adsorption Behavior on Tetracycline Removal from an Aqueous Solution

活化是提高生物炭吸附性能的重要手段.以小麦秸秆为研究对象,KOH为活化剂,制备KOH活化生物炭(K-BC),同时制备原状生物炭(BC)作为对照.对生物炭进行比表面积和孔径、元素分析、XPS、FTIR、Raman、XRD和pHpzc等表征,考察KOH活化对生物炭理化性质的影响,并探究生物炭对水体中四环素的吸附性能和机制.结果表明,KOH活化之后生物炭的比表面积和孔体积可达996.4 m^(2)·g^(-1)和0.45 cm^(3)·g^(-1).KOH活化会制造更多的碳结构缺陷,影响生物炭的官能团和表面电性.拟二级动力学和Langmuir模型可以较好地拟合生物炭吸附四环素的过程.环境温度升高能提高生物炭对四环素的吸附量.K-BC吸附四环素是自发、吸热和无序度增加的过程.K-BC对四环素的最大吸附量理论可达到491.19 mg·g^(-1)(实验温度为45℃).结合吸附后生物炭的Raman、FTIR和XPS表征,发现孔隙填充和π-π作用是K-BC吸附四环素的主要机制,氢键和络合作用也发挥重要作用.此外,K-BC还具有良好的循环使用性能.综上所述,KOH活化小麦秸秆生物炭是有效和可行的,可用于废水中四环素的去除.

Activation modification is an important pathway to improve the adsorption performance of biochar.In this study,modified biochar(K-BC)was prepared from wheat straw,KOH acted as an activator agent,and pristine biochar(BC)was prepared as a control.The biochars were characterized by nitrogen adsorption and desorption,elemental analysis,XPS,FTIR,Raman,XRD,and pH_(pzc).The effect of KOH modification on the physical and chemical properties of biochars was investigated systematically,and the adsorption performance and mechanism of tetracycline on biochars were also explored.The results showed that the specific surface area and pore volume of KOH activated biochar reached 996.4 m^(2)·g^(-1)and 0.45 cm^(3)·g^(-1).KOH activation produced more carbon structural defects and affected functional groups and surface electrical properties in the biochar.Pseudo-second order kinetics and Langmuir models better fitted the adsorption process of tetracycline on biochar.With the increase in temperature,the adsorption capacity of tetracycline on biochar increased accordingly.The adsorption process of TC by K-BC was spontaneous and endothermic and increased randomness.The theoretical maximum adsorption capacity of K-BC for tetracycline was 491.19 mg·g^(-1)(at a 45℃experimental temperature).Combined with the Raman,FTIR,and XPS characterization of biochars after TC adsorption,it was found that pore filling andπ-πinteraction were the main mechanisms for TC removal by K-BC,followed by hydrogen bonding and metal complexation.Further,K-BC presented a good recycling performance.In summary,KOH activation on wheat straw biochar was effective and feasible and could be used to remove tetracycline from wastewater.