Cr(VI) is widely used in industry and often large quantities have been accidently or due to lack of precautions released at the environment. The presence of high concentrations of Cr(VI) in waste streams causes concern due to its toxicity and solubility. However the Cr(III) is a useful micronutrient in human diet. The reduction of Cr(VI) to Cr(III) is a promising technology for a clean environment. Polyphenols are commonly found in plants and they are considered as strong natural antioxidants. In this study the reduction of hexavalent to trivalent chromium using gallic acid (GA), a polyhydroxyphenolic compound, was evaluated. The effect of pH, temperature, and Cr(VI) concentration on the kinetics of Cr(VI) reduction by GA were examined by conducting batch tests. It was found that reduction of Cr(VI) by GA is a rapid reaction under mild acidic conditions. Reduction was found to follow a 2^nd order kinetics with respect to Cr(VI) concentration in the pH range 3-5. The results of the present study indicated that the treatment of contaminated waters with initial concentration of Cr(VI) 100 μΜ by gallic acid, below the environmental limit of 0.96 μM, required 20 min at pH 3 and 40 min at pH 4. At higher pH a different reduction mechanism seems to prevail and the required time for Cr(VI) reduction was approximately 10 hours at pH 5 and 42 hours at pH 6. The increase of temperature25^oC to 35^oC, at pH 6, was slightly accelerated the reaction.

六价铬在工业中被广泛使用，并且经常由于意外或由于缺乏在环境中释放的预防措施而大量使用六价铬。废物流中高浓度的Cr（VI）的存在由于其毒性和溶解性而引起关注。但是，Cr（III）是人类饮食中有用的微量营养素。将Cr（VI）还原为Cr（III）对于清洁环境是一种很有前途的技术。多酚通常存在于植物中，被认为是强天然抗氧化剂。在这项研究中，使用多羟基酚化合物没食子酸（GA）将六价铬还原为三价铬。通过进行批处理测试，考察了pH，温度和Cr（VI）浓度对GA还原Cr（VI）动力学的影响。发现在中等酸性条件下，GA还原Cr（VI）是一种快速反应。发现减少遵循2^第二级动力学与在pH范围3-5相对于铬（VI）的浓度。本研究的结果表明，用没食子酸处理初始浓度为100μM的Cr（VI）的污染水，低于环境极限0.96μM，在pH 3时需要20分钟，在pH 4时需要40分钟。 pH值似乎是一种不同的还原机制，Cr（VI）还原所需的时间在pH值为5时约为10小时，在pH值为6时约为42小时。在pH 6时，温度从25 ^o C升高至35 ^o C的过程有所加快。反应。