Understanding the mechanism of metal adsorption on polysaccharides possesing suparamolecular structure and molecular design of separation materials

生物吸附是指生物质吸附金属离子的过程，是一种具有潜在成本效益的消除有毒重金属的方法。随着微生物去除水溶液中金属离子的能力得到广泛的研究，真菌已被认为是一类有前途的低成本金属离子吸附剂。研究了寡孢根霉（Rhizopus oligo.）在液体培养基中发酵对镧烷、铜和钴的吸附性能。在rh。物种,Rh.oligo。P12表现出最高的金属吸附能力，为3.2 mmol/g-菌丝，与传统的离子交换珠相媲美，用于废水处理。通过吸附等温线、Freundlich曲线和Scatchard图分析，得到了Rh.oligo中的几种官能团。发现P12有助于金属吸附。pH依赖性的斜率分析表明，离子交换不是菌丝与铜、镧和钴等金属相互作用的主要因素。这些结果表明细胞壁中的多糖参与了金属吸附。为了阐明多糖的超分子结构与金属吸附能力之间的关系，我们对各种含多糖的生物质进行了吸附实验。例如，我们利用含有复数羟基的纤维素作为锑（III）吸附剂。纤维素吸附锑（III）的量最大为5.2mg/g。两个多元醇基团的两个相邻羟基在纤维素的葡萄糖单元中，纤维素可以用游离羟基捕获锑（III），即不形成氢键的羟基。

Biosorption, the metal-ion adsorption process by biomass, represents a potentially cost-effective way of eliminating toxic heavy metals. As the ability of microorgamisms to remove metal ions in aqueous solution has been extensively studied, fungi have been recognized as a promising class of low-cost adsorbents for metal ions. Adsorption performance of lanthane, copper, and cobalt by Rhizopus oligosporus (Rh.oligo.) fermented in liquid media was investigated. Among the Rh.oligo. species, Rh.oligo. P12 demonstrated the highest metal-adsorption capacity of 3.2 mmol/g-mycelia, which was comparable to the conventional ion-exchange beads for wastewater treatments. From the adsorption isotherm, the Freundlich curve, and the Scatchard plot analysis, the several kinds of functional groups in Rh.oligo. P12 were found to contribute to the metal adsorption. The slope analysis of the pH dependence showed that the ion-exchange is not a dominant factor of the interactions between the mycelia and metals such as copper, lanthane and cobalt. These results indicated that the polysaccharides in cell wall were involved in the metal adsorption. We carried out the adsorption tests with various kinds of biomass containing polysaccharides in order to elucidate the relationship between the supramolecular structure of polysaccharides and the metal adsorption ability. For example, we have utilized the cellulose containing the plural hydroxyl groups as the antimony (III) adsorbent. Amount of antimony (III) adsorbed to the cellulose was 5.2mg/g at maximum. Two adjacent hydroxyl groups of two polyol moieties are in the glucose unit of cellulose, cellulose could capture antimony (III) with free hydroxyl groups, that is, non-hydrogen-bonding-forming hydroxyl groups.