Ayala Julia, Fernández Begoña
a Departamento de Ciencia de Materiales e Ingeniería Metalúrgica, Universidad de Oviedo , Oviedo , Spain.
Environ Technol. 2019 Jun;40(15):2037-2051. doi: 10.1080/09593330.2018.1435739. Epub 2018 Feb 15.
The removal of heavy metals from mining waste leachate by spent coffee grounds has been investigated. In synthetic solutions, metal uptake was studied in batch adsorption experiments as a function of pH, contact time, initial metal concentration, adsorbent concentration, particle size, and the effect of co-ions (Na, K, Ca, Mg, Cu, Cd, Ni, Zn). Results showed that adsorption was significantly affected by pH, showing the highest affinity within a pH range of 5-7. Sorption of heavy metals reached equilibrium in 3 h. Removal percentages of metals ions increased with increasing dosage. Particle size did not have a significant influence on metal uptake. The adsorption of heavy metals was found to fit Langmuir and Freundlich isotherms. Maximum Zn, Cd and Ni uptake values were calculated as 10.22, 5.96 and 7.51 mg/g, respectively, using unwashed coffee grounds (UCG) as the adsorbent and 5.36, 4.28 and 4.37 mg/g when employing washed coffee grounds as the adsorbent. The presence of co-ions inhibited the uptake of heavy metals, divalent ions having a more negative effect than monovalent ions. The results obtained in the experiments with mining waste leachate showed that UCG is effective in removing heavy metals.
已对用过的咖啡渣去除采矿废浸出液中重金属的情况进行了研究。在合成溶液中，通过批量吸附实验研究了金属吸附情况，该实验考察了pH值、接触时间、初始金属浓度、吸附剂浓度、颗粒大小以及共存离子（Na、K、Ca、Mg、Cu、Cd、Ni、Zn）的影响。结果表明，吸附受pH值影响显著，在pH值为5 - 7的范围内吸附亲和力最高。重金属的吸附在3小时内达到平衡。金属离子的去除率随用量增加而提高。颗粒大小对金属吸附没有显著影响。发现重金属的吸附符合朗缪尔等温线和弗伦德利希等温线。以未清洗的咖啡渣（UCG）作为吸附剂时，锌、镉和镍的最大吸附量分别计算为10.22、5.96和7.51 mg/g，而以清洗过的咖啡渣作为吸附剂时，最大吸附量分别为5.36、4.28和4.37 mg/g。共存离子的存在抑制了重金属的吸附，二价离子的负面影响比一价离子更大。在采矿废浸出液实验中获得的结果表明，UCG在去除重金属方面是有效的。
