Papandreou A, Stournaras C J, Panias D
CERECO S. A. Ceramics and Refractories Technological Development Company, 72nd Km. of Athens-Lamia National Road, P.O. Box 18946, 34100 Chalkida, Greece.
J Hazard Mater. 2007 Sep 30;148(3):538-47. doi: 10.1016/j.jhazmat.2007.03.020. Epub 2007 Mar 12.
Studies on the utilization of low cost adsorbents for removal of heavy metals from wastewaters are gaining attention. Fired coal fly ash, a solid by-product that is produced in power plants worldwide in million of tonnes, has attracted researchers' interest. In this work, fly ash was shaped into pellets that have diameter in-between 3-8mm, high relative porosity and very good mechanical strength. The pellets were used in adsorption experiments for the removal of copper and cadmium ions from aqueous solutions. The effect of agitation rate, equilibration time, pH of solution and initial metal concentration were studied. The adsorption of both cations follows pseudo-second order kinetics reaching equilibrium after an equilibration time of 72 h. The experimental results for copper and cadmium adsorption fit well to a Langmuirian type isotherm. The calculated adsorption capacities of pellets for copper and cadmium were 20.92 and 18.98 mg/g, respectively. Desorption experiments were performed in several extraction media. The results showed that both metals were desorbed substantially from pellets under acidic solutions. For this reason, metal saturated pellets were encapsulated in concrete blocks synthesized from cement and raw pulverized fly ash in order to avoid metal desorption. The heavy metals immobilization after encapsulation in concrete blocks was tested through desorption tests in several aqueous media. The results showed that after 2 months in acidic media with pH 2.88 and 4.98 neither copper nor cadmium were desorbed thus indicating excellent stabilization of heavy metals in the concrete matrix. As a conclusion, the results showed that fly ash shaped into pellets could be considered as a potential adsorbent for the removal of copper and cadmium from wastewaters. Moreover, the paper proposes an efficient and simple stabilization process of the utilized adsorbents thus guarantying their safe disposal in industrial landfills and eliminating the risk of pollution for groundwater and other natural water receivers.
利用低成本吸附剂去除废水中重金属的研究正受到关注。燃煤飞灰作为一种固体副产品，在全球发电厂每年以数百万吨的规模产生，已引起研究人员的兴趣。在这项工作中，飞灰被制成直径在3 - 8毫米之间、具有较高相对孔隙率和良好机械强度的颗粒。这些颗粒用于吸附实验，以去除水溶液中的铜离子和镉离子。研究了搅拌速率、平衡时间、溶液pH值和初始金属浓度的影响。两种阳离子的吸附均符合准二级动力学，平衡时间72小时后达到平衡。铜和镉吸附的实验结果与朗缪尔等温线拟合良好。计算得出颗粒对铜和镉的吸附容量分别为20.92和18.98毫克/克。在几种萃取介质中进行了解吸实验。结果表明，在酸性溶液中两种金属都能从颗粒中大量解吸。因此，将金属饱和颗粒封装在由水泥和原始粉煤灰合成的混凝土块中，以避免金属解吸。通过在几种水性介质中的解吸试验，测试了封装在混凝土块中后重金属的固定情况。结果表明，在pH值为2.88和4.98的酸性介质中放置2个月后，铜和镉均未解吸，这表明重金属在混凝土基质中具有良好的稳定性。总之，结果表明，制成颗粒的飞灰可被视为一种潜在的吸附剂，用于去除废水中的铜和镉。此外，本文提出了一种有效且简单的利用吸附剂的稳定化工艺，从而保证其在工业垃圾填埋场的安全处置，并消除对地下水和其他天然水体的污染风险。
