真菌发酵有效提升秸秆炭有机污染物吸附性能

Fungal fermentation enhances organic pollutant adsorption performance of straw biochar

摘要:

背景 我国农业废弃秸秆存量大，微生物发酵无法实现其彻底转化，仍造成二次污染和资源浪费的问题。秸秆发酵废弃物可经热解炭化制备吸附剂用于水体有机污染物的高效去除。 目的 探究以秸秆发酵废弃物为原料所制备秸秆炭对有机污染物的去除效率，明确发酵过程对秸秆炭吸附性能的影响及机制，为水体有机污染物的高效去除和秸秆发酵废弃物的再利用提供参考。 方法 以丝状真菌里氏木霉QM6a和棘孢木霉T-1为发酵菌株，分别对小麦和水稻秸秆进行固态发酵，发酵残渣经热解炭化后用于吸附典型有机偶氮染料亚甲基蓝(methylene blue, MB)。 结果 发酵处理可缩短吸附平衡时间，有效提高小麦秸秆炭对MB的吸附效率，但对水稻秸秆炭吸附性能无明显提升作用。棘孢木霉T-1发酵的小麦秸秆经600 ℃热解所得秸秆炭(BaWS 600)对MB (50 mg/L)的吸附效率较天然秸秆炭(BWS 600)提高53.6%。准二级动力学模型可有效模拟吸附过程，BaWS 600的平衡吸附量比BWS 600和BWS 800高119.4%和299.4%。Freundlich模型可较好描述等温吸附过程，表明MB在秸秆炭表面的吸附为多分子层吸附。秸秆发酵将小麦秸秆炭比表面积提高47.4%‒245.8%不等，且可增加热解炭化产物表面含氧官能团丰富度，是MB吸附效率得以有效提升的主要原因。 结论 真菌发酵过程可有效改善秸秆炭性状和污染物吸附性能，而棘孢木霉T-1因具有更优的纤维素酶分泌能力，更适合作为发酵菌株用于改良秸秆炭污染物吸附性能。

Abstract:

Background China has abundant waste straw. The incomplete transformation of straw by microbial fermentation causes secondary pollution and resource wastes. The wastes from straw fermentation can be carbonized to prepare the adsorbent for removing organic pollutants from water. Objective To investigate the pollutant removal efficiency of biochar prepared from fermented straw, clarify the effects of fermentation process on the properties of straw biochar, and finally provide a theoretical basis for reusing the wastes from straw fermentation and removing organic pollutants from water. Methods Solid-state fermentation of wheat straw and rice straw was carried out with Trichoderma reesei QM6a and T. asperellum T-1, respectively. The fermentation residues were then pyrolyzed to adsorb methylene blue (MB). Results The fermentation of straw effectively shortened the time to adsorption equilibrium and improved the MB adsorption efficiency of wheat straw biochar. The adsorption efficiency of MB (50 mg/L) by the biochar pyrolyzed at 600 ℃ from wheat straw pre-fermented by T. asperellum T-1 (BaWS 600) was 53.6% higher than that from natural straw (BWS 600). The pseudo-second-order model could well fit the adsorption process, and the MB adsorption capacity of BaWS 600 was 119.4% and 299.4% higher than that of BWS 600 and BWS 800, respectively. Freundlich isothermal adsorption equation could well characterize the isothermal adsorption process, which indicated the multi-molecular layer adsorption of MB by straw biochar. Straw fermentation increased the specific surface area of wheat straw biochar by 47.4% to 245.8% and promoted the exposure of oxygen-containing functional groups, which might be the main reasons for the improvement of MB adsorption efficiency. Conclusion Fermentation can effectively improve the properties of straw biochar for pollutant removal. T. asperellum T-1 was identified to be more suitable for straw fermentation to improve the pollutant adsorption performance of biochar because of its stronger cellulase-secreting ability.