生物炭内源溶解性有机物的释放对 RhB 吸附的影响

Effect of Release of Endogenous DOM in Biochar on RhB Adsorption

生物炭所释放的溶解性有机物(DOM)可能会与污染物相互作用,但DOM的组分及其在生物炭吸附过程中的影响机制尚不清楚。研究对不同热解温度制备的生物炭释放的DOM进行表征,分析其组分和理化性质,通过吸附动力学和吸附等温试验探究DOM在生物炭吸附RhB的过程中的影响机制。结果表明,热解温度和生物质原料均会影响DOM的组分,低温生物炭(300℃)比高温生物炭(500℃和700℃)能释放出更多的DOM,玉米秸秆生物炭的DOM释放量高于松木锯末生物炭,低温生物炭释放的DOM主要组分为富里酸类物质和腐植酸类物质,且其极性指数与生物炭相反。吸附试验表明,DOM的添加延长了酸改性生物炭对罗丹明B(RhB)的吸附平衡时间(90 min→210 min),同时也大大降低了酸改性生物炭对RhB的吸附量(ACS300:7.86 mg/g→2.26 mg/g;APS300:6.41 mg/g→1.61 mg/g),DOM可以与RhB形成络合物(吸附率:14.29%~30.77%),从而抑制其在生物炭上的吸附。此外,还发现DOM的富里酸类和腐植酸类含量与生物炭的吸附量呈负相关。因此,DOM释放量越多,生物炭对RhB吸附效率越低。

The dissolved organic matter(DOM)released by biochar may interact with pollutants,but the composition of DOM and its influence mechanism in biochar adsorption process are still unclear.In this study,the components and physicochemical properties of DOM released from biochar prepared at different pyrolysis temperatures were characterized and analyzed.The influence mechanism of DOM on the adsorption of RhB by biochar was investigated by adsorption kinetics and adsorption isotherm experiments.The results showed that both pyrolysis temperature and biomass raw materials affected the composition of DOM.Low-temperature biochar(300℃)could release more DOM than high-temperature biochar(500℃and 700℃).The DOM release of corn straw biochar was higher than that of pine sawdust biochar.The main components of DOM released by low-temperature biochar were fulvic acid-like substances and humic acid-like substances,and its polarity index was opposite to that of biochar.Adsorption experiments showed that the addition of DOM prolonged the adsorption equilibrium time of acid modified biochar to RhB(90 min→210 min),and also greatly reduced the adsorption capacity of acid modified biochar to RhB(ACS300:7.86 mg/g→2.26 mg/g;APS300:6.41 mg/g→1.61 mg/g),DOM could form a complex with RhB(adsorption rate:14.29%~30.77%),thereby inhibiting its adsorption on biochar.In addition,it was found that the content of fulvic acid and humic acid in DOMs was negatively correlated with the adsorption capacity of biochar.Therefore,the more DOM released,the lower the adsorption efficiency of biochar on RhB.