Hexavalent chromium was adsorbed from aqueous solution with three prepared and characterized adsorbents, namely goethite (G), activated carbon (AC) and their composite (GAC). The goethite particle was synthesized using the precipitation methods, and activated carbon was prepared from the stem bark of Daniellia oliveri tree and composite in a ratio of 1:5 goethite–activated carbon. The adsorption capacities of G, AC and GAC for Cr(VI) are 6.627, 5.455 and 6.354 mg/g with 0.02 g adsorbent within contact time of 60, 180 and 30 min for G, AC and GAC, respectively, for Cr(VI) adsorption at optimum pH of 3. The isotherm studied was best explained by Langmuir adsorption isotherm and fitted with the pseudo-second-order kinetic model. Desorption studies showed that 1.0 M HNO₃ was a better desorbing agent than 0.1 M HNO₃, 0.1 M HCl and 1.0 M HCl. Chromium was most desorbed (94.60% in Cr//G using 1 M HNO₃). The result obtained revealed that goethite and activated carbon produced are favourable adsorbents and the composite of the two adsorbents gives a more favourable, economical and affordable adsorbent for the clean-up of heavy metal contamination.

中文翻译：

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Cr（VI）离子在针铁矿，活性炭及其复合材料上的吸附：动力学和热力学研究

用三种制备的和表征的吸附剂（针铁矿（G），活性炭（AC）及其复合物（GAC））从水溶液中吸附六价铬。用沉淀法合成针铁矿颗粒，并用丹尼尔利亚橄榄树的茎皮和复合物按1：5的针铁矿活性炭比例制备活性炭。G，AC和GAC对Cr（VI）的吸附容量分别为6.627、5.455和6.354 mg / g，其中0.02 g吸附剂在Cr（VI）的G，AC和GAC接触时间分别为60、180和30分钟内。 ）在3的最佳pH值下吸附。等温线最好用Langmuir吸附等温线解释，并符合拟二级动力学模型。解吸研究表明1.0 M HNO ₃是一个更好的解吸附试剂比的0.1M HNO ₃，0.1M HCl和1.0M的HCl中。铬最易解吸（使用1 M HNO _3时，Cr // G中的94.60％）。所得结果表明，针铁矿和活性炭是有利的吸附剂，两种吸附剂的复合物为清洁重金属污染物提供了更有利，经济和负担得起的吸附剂。