Industrial discharges loaded with heavy metals present several problems for aquatic ecosystems and human health. In this context, the present study aims to evaluate the potential of raw spent coffee grounds to remove chromium from an aqueous medium. A structural and textural study of coffee grounds was carried out by FTIR, XRD, and TGA analysis. The optimum conditions for the removal of Cr(VI), for a solution with an initial concentration of 100 mg/l, were adsorbent dose 2.5 g/l, pH 4.0, and contact time 90 min. The adsorption equilibrium results show that the Langmuir isotherm best describes the process with an adsorption capacity of 42.9 mg/g and that the adsorption kinetics follows the pseudosecond-order model. The calculated thermodynamic parameters showed that the adsorption is exothermic and spontaneous. The activation energy value (E_a) indicated that the retention is physisorptive in nature. The regeneration of the adsorbent was carried out by three eluents, among which HCl was the best. Finally, a brief cost estimation showed the great potential of coffee grounds as a low-cost adsorbent.

中文翻译：

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评估未经处理的咖啡废物以去除水介质中的铬 (VI)

含有重金属的工业排放物给水生生态系统和人类健康带来了几个问题。在这种情况下，本研究旨在评估生咖啡渣从水性介质中去除铬的潜力。通过 FTIR、XRD 和 TGA 分析对咖啡渣进行了结构和质地研究。对于初始浓度为 100 mg/l 的溶液，去除 Cr(VI) 的最佳条件是吸附剂量 2.5 g/l、pH 4.0 和接触时间 90 分钟。吸附平衡结果表明，Langmuir 等温线最能描述吸附容量为 42.9 mg/g 的过程，并且吸附动力学遵循伪二级模型。计算的热力学参数表明吸附是放热和自发的。活化能值（E _a ) 表明保留本质上是物理吸附的。吸附剂的再生采用三种淋洗液进行，其中盐酸最好。最后，简要的成本估算表明咖啡渣作为低成本吸附剂的巨大潜力。