ABSTRACT

Over the last decades, adsorption has emerged as a potential separation process for the removal of heavy metals that are extensively released in effluents from different industries. Among heavy metals, Cr(VI) is relevant due to its high toxicity, and its required concentration limit between 50 and 100 µg/L in water for human consumption. Several adsorbents, including silica, zeolites, clays, and carbon, are expensive for this application. This literature review proposed the use of novel adsorbents based on polysaccharides, mainly chitosan and cellulose, generalizing the effect of pH, equilibrium, kinetics, thermodynamics, and mechanism on the adsorption efficiency. It is shown that chitosan and cellulose exhibit a competitive Cr(VI) adsorption capacity reaching up to 625 and 358 mg/g, respectively. Also, a general review of sorbent reusability and continuous-flow adsorption is provided as they are critical for the highly extensive operation where maximum continuous-flow removals of 350 and 93 mg/g are reported for chitosan and cellulose. The use of polysaccharides as sorbents in batch and semi-continuous systems is an area of great interest and an opportunity to direct the efforts to provide state-of-the-art sorbents and technology for the removal of hexavalent chromium from polluted water streams.

摘要

在过去的几十年里，吸附已成为一种潜在的分离过程，用于去除不同行业废水中大量释放的重金属。在重金属中，Cr(VI) 具有较高的毒性，并且在人类食用的水中要求浓度限制在 50 到 100 µg/L 之间。几种吸附剂，包括二氧化硅、沸石、粘土和碳，对于该应用来说是昂贵的。这篇文献综述提出了使用基于多糖的新型吸附剂，主要是壳聚糖和纤维素，概括了 pH 值、平衡、动力学、热力学和机理对吸附效率的影响。结果表明，壳聚糖和纤维素具有竞争性的 Cr(VI) 吸附容量，分别达到 625 和 358 mg/g。还，提供了对吸附剂可重复使用性和连续流吸附的一般审查，因为它们对于高度广泛的操作至关重要，据报道，壳聚糖和纤维素的最大连续流去除量为 350 和 93 毫克/克。在分批和半连续系统中使用多糖作为吸附剂是一个非常有趣的领域，也是引导努力提供最先进的吸附剂和技术以从污水流中去除六价铬的机会。