Effect of Release of Endogenous DOM in Biochar on RhB Adsorption
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.
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