Bai R Sudha, Abraham T Emilia
Biochemical Processing & Wastewater Technology Division, CSIR Regional Research Laboratory, Trivandrum, India.
Water Res. 2002 Mar;36(5):1224-36. doi: 10.1016/s0043-1354(01)00330-x.
This study reports the biosorption of Cr(VI) by chemically modified biomass of Rhizopus nigricans and the possible mechanism of Cr complexation to the adsorbent. The cell wall of this fungus possesses strong complexing property to effectively remove Cr(VI) anions from solution and wastewater. The mechanism of Cr adsorption by R. nigricans was ascertained by chemical modifications of the dead biomass followed by FTIR spectroscopic analysis of the cell wall constituents. Treatment of the biosorbent with mild alkalies (0.01 N NaOH and ammonia solution) and formaldehyde (10%, w/v) deteriorated the biosorption efficiency. However, extraction of the biomass powder in acids (0.1 N HCl and H2SO4), alcohols (50% v/v, CH3OH and C2H5OH) and acetone (50%, v/v) improved the Cr uptake capacity. Reaction of the cell wall amino groups with acetic anhydride reduced the biosorption potential drastically. Blocking of the-COOH groups by treatment with water soluble carbodiimide also resulted in initial lag in Cr binding. Biomass modification experiments conducted using Cetyl Trimethyl Ammonium Bromide (CTAB), Polyethylenimine (PEI), and Amino Propyl Trimethoxy Silane (APTS) improved the biosorption efficiency to exceptionally high levels. The FTIR spectroscopic analysis of the native, Cr bound and the other types of chemically modified biomass indicated the involvement of amino groups of Rhizopus cell wall in Cr binding. The adsorption data of the native and the most effectively modified biomass were evaluated by the Freundlich and the Langmuir adsorption isotherms and the possible adsorption phenomena are also discussed.
本研究报道了黑根霉化学修饰生物质对Cr(VI)的生物吸附作用以及Cr与吸附剂络合的可能机制。这种真菌的细胞壁具有很强的络合特性，能够有效去除溶液和废水中的Cr(VI)阴离子。通过对死生物质进行化学修饰，随后对细胞壁成分进行傅里叶变换红外光谱(FTIR)分析，确定了黑根霉对Cr的吸附机制。用弱碱(0.01 N NaOH和氨溶液)和甲醛(10%，w/v)处理生物吸附剂会降低生物吸附效率。然而，用酸(0.1 N HCl和H2SO4)、醇(50% v/v，CH3OH和C2H5OH)和丙酮(50%，v/v)萃取生物质粉末可提高Cr的吸收能力。细胞壁氨基与乙酸酐反应会大幅降低生物吸附潜力。用水溶性碳二亚胺处理封闭-COOH基团也会导致Cr结合初期出现滞后现象。使用十六烷基三甲基溴化铵(CTAB)、聚乙烯亚胺(PEI)和氨基丙基三甲氧基硅烷(APTS)进行的生物质修饰实验将生物吸附效率提高到了极高水平。对天然的、Cr结合的以及其他类型化学修饰生物质的FTIR光谱分析表明，黑根霉细胞壁的氨基参与了Cr的结合。通过Freundlich和Langmuir吸附等温线对天然的和修饰最有效的生物质的吸附数据进行了评估，并讨论了可能的吸附现象。
