Preparation Of New Adsorbents And Adsorption Of Copper Ions

In recent years, with the acceleration of China's industrialization process and the rapid development of economic construction, water pollution caused by industrialization and economic development becomes increasingly serious, leading the trace heavy metals and toxic organic pollutants in source of drinking water in many cities were significantly increased. The security situation of water quality becomes worse. New environmental-friendly, efficient and advanced adsorption materials have become the hot research topic for water purification in the world. In this paper, carbon nanotubes, a new type of nanomaterials with properties quite different from the conventional adsorption materials, are used as a supportor. The new composite materials (Fe2O3/CNT) are prepared by liquid chemical deposition method, which can remove the divalent copper ions (Cu2+) efficiently. In addition, one new composite adsorbent, kaolin/calcium alginate (kaolin/CA), is fabricated using a sol-gel method. The adsorption behaviors and adsorption mechanism of Cu2+ adsorbed by kaolin/CA have been investigated in detailed.The method of liquid chemical deposition is used to form the composite adsorbent with carbon nanotubes and Fe2O3. From the SEM pictures of original CNT, CNT oxidized by mixed acids and Fe2O3/CNTs, it can be observed that after being oxidized by mixed acids, the carbon nanotubes become shorter, the end caps are opened at both ends. Also we can see that the loaded Fe2O3 is deposited uniformly. The Cu2+ removal efficiencies of original CNT, CNT oxidized by mixed acids and Fe2O3/CNTs are compared through the experiments of adsorption isotherms. The order of the adsorption capabilities is Fe2O3/CNT>oxidized CNT>original CNT. Langmuir model is used to fit the experimental data, the maximum adsorption capacity of Fe2O3/CNTs for Cu2+ reaches 42.02 mg g-1. The pH of the solution has great effects on the adsorption capacity and removal efficiency of Fe2O3/CNTs for Cu2+. The adsorption capacity of Fe2O3/CNTs for Cu2+ will decrease with decreasing the solution pH value.A novel environmental-friendly material, kaolin immobilized by calcium alginate (kaolin/CA), was prepared by using sol-gel method. The new adsorbent can be separated and removed easily from water solution and effectively avoid the secondary pollution problem caused by the mirco-sized kaolin. The effects of contact time, pH, adsorbent dose and temperature on Cu2+ adsorption by the kaolin/CA were investigated. The Langmuir isotherm was used to describe the experimental data and the maximum Cu2+ adsorption capacity of the kaolin/CA reached 53.63 mg g-1, which had a great increase compared to 5.06 mg g-1 of pure kaolin. The kinetic studies showed that the pseudo second-order rate equation could fit the experimental data well. The thermodynamic studies showed that the adsorption reaction was a spontaneous and endothermic process.The research shows that the Fe2O3/CNTs and kaolin/CA have greater removal capacities for the heavy metal cationes in the solution than some other conventional materials. It also provides an efficient, economic and easy approach to handle hazardous trace ion solution.