Onyancha Douglas, Mavura Ward, Ngila J Catherine, Ongoma Peter, Chacha Joseph
Department of Chemistry, Nelson Mandela Metropolitan University, South Africa.
J Hazard Mater. 2008 Oct 30;158(2-3):605-14. doi: 10.1016/j.jhazmat.2008.02.043. Epub 2008 Mar 10.
Chromium in the effluent is a major concern for tanning industry. Chemical precipitation methods are commonly employed for the removal of chromium but this leads to formation of chrome-bearing solid waste, plus it is uneconomical when the concentration of chromium in the effluent is low. Ion exchange and membrane separation methods are relatively expensive. In this study, two algae namely, Spirogyra condensata and Rhizoclonium hieroglyphicum have been employed to remove chromium from tannery effluent. The effect of pH and chromium concentration showed S. condensata to exhibit maximum uptake of about 14 mg Cr(III)/g of algae at optimum pH of 5.0 whereas R. hieroglyphicum had 11.81 mg of Cr(III)/g of algae at pH of 4.0. Langmuir and Freundlich models were applied. Increase of initial concentration of Cr resulted to a decrease in adsorption efficiency. Dilute sulphuric acid (0.1M) showed good desorption efficiency (>75%). Interference from cations negatively impacted on biosorption of chromium. Immobilized algae on Amberlite XAD-8 in a glass column, gave better recovery of chromium in tannery effluent compared to a batch method with unimmobilized algae. Fourier transform infra red (FT-IR) analysis of the two algae revealed the presence of carboxyl groups as possible binding sites.
废水中的铬是制革工业主要关注的问题。化学沉淀法通常用于去除铬，但这会导致含铬固体废物的形成，而且当废水中铬浓度较低时不经济。离子交换和膜分离方法相对昂贵。在本研究中，两种藻类，即凝聚水绵和象形根枝藻，已被用于从制革废水中去除铬。pH值和铬浓度的影响表明，凝聚水绵在最佳pH值5.0时对铬（III）的最大吸收量约为14 mg/g藻类，而象形根枝藻在pH值4.0时对铬（III）的吸收量为11.81 mg/g藻类。应用了朗缪尔和弗伦德利希模型。铬初始浓度的增加导致吸附效率降低。稀硫酸（0.1M）显示出良好的解吸效率（>75%）。阳离子的干扰对铬的生物吸附有负面影响。与使用未固定化藻类的分批方法相比，在玻璃柱中将藻类固定在Amberlite XAD-8上，能更好地回收制革废水中的铬。对这两种藻类的傅里叶变换红外（FT-IR）分析表明，存在羧基作为可能的结合位点。
