槟榔渣生物炭对水中亚甲基蓝的吸附特性及机制

Adsorption characteristics and mechanism of methylene blue in aqueous solution by areca residue biochar

分别在300、500、700℃条件下对废弃槟榔渣进行慢速热解180 min制得槟榔渣生物炭ARB_(300)、ARB_(500)、ARB_(700),探讨了其对水中亚甲基蓝(MB)的吸附性能及动力学、热力学特征,并通过电镜扫描、比表面积分析、红外光谱分析等手段对吸附机制进行了解析。结果表明,当溶液初始pH为9,ARB_(300)、ARB_(500)、ARB_(700)投加质量浓度分别为1.0、0.7、0.5 g/L时,MB去除率均高于95%。准二级动力学模型和Langmuir等温吸附模型能更真实地反映MB在ARB上的吸附行为特征,该吸附行为符合单分子层化学吸附规律。热力学分析表明,吸附反应的ΔG<0,ΔH>0,ΔS>0,反映出ARB对MB的吸附是自发、吸热且熵驱动的过程。具体吸附机制涉及静电引力、孔隙填充、π-π作用、氢键作用等。ARB_(700)对MB的理论最大吸附量达86.51~97.78 mg/g,分别比ARB_(300)、ARB_(500)相应的值提高了72.54%~85.37%、6.31%~8.30%,可作为废水中MB的高效吸附材料。

Wasted areca residue biochars ARB_(300),ARB_(500)and ARB_(700)were produced by slow pyrolysis of waste areca residue at 300,500 and 700℃for 180 min,respectively.Their adsorption properties,kinetics and thermodynamic characteristics for MB in aqueous solution were explored.The adsorption mechanism was discussed by SEM,BET and FTIR analysis.The results indicated that the MB removal rate was higher than 95%when the initial solution pH was9 and the ARB_(300),ARB_(500)and ARB_(700)dosage were 1.0,0.7 and 0.5 g/L,respectively.The quasi second-order kinetic model and Langmuir isothermal adsorption model could more truly reflect the adsorption behavior characteristics of MB on ARB,which was in line with the law of monolayer chemical adsorption.Thermodynamic analysis showed that the adsorption reactionΔG<0,ΔH>0,ΔS>0,reflecting that the adsorption of MB by ARB was a spontaneous,endothermic and entropy driven process.The specific adsorption mechanisms included electrostatic gravitation,pore filling,π-πbonding and hydrogen bonding,etc.The theoretical maximum MB adsorption capacity of ARB_(700)was up to 86.51-97.78 mg/g,which was 72.54%-85.37%and 6.31%-8.30%higher than that of ARB_(300)and ARB_(500)respectively.It could be considered as a high-performance adsorption material for eliminating MB from wastewater.