污泥液化生物炭对亚甲基蓝的吸附特性及机理

Characteristic and mechanism of methylene blue adsorption by biochar from the liquefaction of sewage sludge

探讨污泥在乙醇-水混合溶剂中液化产生的生物炭的吸附潜力及其吸附机理(以亚甲基蓝(MB)废水为处理对象),结果表明:生物炭的吸附容量随着MB溶液起始pH值升高而升高,当pH超过8时,MB的碱性褪色开始显现.吸附温度的上升(30~60℃)对生物炭吸附容量的影响不明显.吸附容量总体上随着吸附时间的增加而上升(240min前),在240min后趋于稳定.吸附剂用量及初始MB浓度过高或过低都不利于生物炭的吸附,存在一个的临界点,分别是6mg和120mg/L.生物炭吸附MB的过程吻合准二级动力学方程(R^2=0.9994)和Langmuir方程(R^2=0.9831),且为自发吸热的过程,受物理吸附和化学吸附联合控制,具体的机理包括:离子交换、官能团络合、π-π吸附等.

The purpose of this study was to investigate the adsorption potential/mechanism of biochar obtained from the liquefaction of sewage sludge in ethanol-water co-solvent,which could provide data support and theoretical reference for its application as adsorbent.Methylene blue wastewater was selected as the treatment object.The results showed that the adsorption capacity of biochar firstly increased with the increase of initial pH of MB solution.When the pH of MB solution was higher than 8,the alkaline fading of MB began to appear.The increase of adsorption temperature(30~60℃)had no obvious effects on the adsorption capacity of biochar.The adsorption capacity of biochar overall increased with the increase of adsorption time before 240min.When the adsorption time exceeded 240 min,the adsorption capacity tended to be stable.Too high or too low adsorbent dosage and initial MB concentration were both not beneficial for the adsorption process.Both of them had an optimal critical value of 6mg and 120mg/L,respectively.The adsorption process of MB by biochar matched perfectly with the pseudo-second-order model(R^2=0.9994)and the Langmuir model(R^2=0.9831),respectively.The adsorption process was spontaneous and endothermic,controlled by both physical and chemical adsorption.The specific adsorption mechanisms include ion exchange,functional group complexation,π-πadsorption,and so on.