The Preparation And Application Of Typical Solid Waste Based Adsorbent

With the fast development of economic, the problems of heavy metal waste water pollution have become more serious. Traditional treatment of heavy metal waste water pollution has some problems such as high cost, incomplete adsorption and secondary pollution, resulting that it is difficult to meet the requirements of contemporary multi-faceted development. How to clear up the metal waste water pollution economically, effectively and environment friendly is the prominent problem. Municipal solid waste based adsorbent has received a lot of publicity because it has many advantages, including fast adsorption rate, abundant resource, low cost, easy cycle and well adsorption properties. Typical solid waste was chosen as the raw material to prepare carbon-based adsorbent, which was used to solve the problem of heavy metals in waste water pollution, which has a wide application prospect.Typical solid wastes such as wood, acrylic fabric, tire powder and rice husk were chosen as the raw material to prepare carbon-based adsorbent, using the method of KOH and steam activation. The adsorption behaviors of heavy metal ions, including Cu2+, Pb2+and Zn2+ were investigated. Use FT-IR, surface analyzer, Boehm titration, SEM, EDS and XPS to determine the characterizations of carbon-based adsorbent. The effects of solution pH, temperature, adsorption time, and adsorbent dosage on the adsorption process were investigated. The adsorption thermodynamic, adsorption kinetics and adsorption isotherms were studied. Three chemical modification methods were used for carbon-based to prepare modified carbon-based adsorbent. The changes of the adsorption capacities for Cu2+, Pb2+ and Zn2+ by carbon-based adsorbent and modified carbon-based adsorbent were investigated. Furthermore, the performance of desorption and reuse for carbon-based adsorbent and competitive adsorption behavior of metal ions system were analyzed too. At last, the adsorption mechanisms were discussed.From the adsorption behaviors for Cu2+, Pb2+ and Zn2+, it is concluded that the adsorption capacities increases with increasing solution pH; all the adsorption processes could be well described by the pseudo-second-order equation. The adsorption of Cu2+, Pb2+ and Zn2+ by carbon-based adsorbents which from AC1 to AC8 fitted Langmuir model better by analyzing the adsorption isotherms. The analysis of D-R isotherm equation shows that the adsorption processes of Cu2+, Pb2+ and Zn2+ by AC1-AC8 belong to chemical adsorption mostly, but both physical adsorptions. The adsorption capacities for Cu2+, Pb2+ and Zn2+ by carbon-based adsorbents was less than modified carbon-based adsorbent (modified by HNO3), it is explained that using chemical modification processes can improve the adsorption ability successfully by adding functional groups. Adsorbents could be reused by using 0.1mol/L HCl solution.With the analysis of the change of solution pH before and after heavy metal adsorption, the adsorption mechanism of carbon-based adsorbents was mainly due to ion exchange and functional groups (-OH,-COOH) on the surface of carbon-based adsorbents. The change of XPS spectra peak area before and after adsorption, which may be due to the exchange of heavy mental ions Pb2+ and Zn2+ and functional group (-COOH); The adsorption mechanisms of metal ions by carbon-based adsorbents AC1-AC8 belong to chemical adsorption mostly, but both physical adsorptions.The competitive adsorption behavior for metal ions solutions by AC1, AC2, AC3 and AC8 were discussed. Use Carbon-based adsorbents AC1, AC2, AC3 and AC8 to test the competitive adsorption behaviors of two metal ions systems:Cu2+/Pb2+(Cu2+ is another metal ion), Zn2+/Pb2+ Pb2+/Cu2+ and Pb2+/Zn2+. It is concluded that the effect of the coexistence of Cu2+ or Zn2+ ions in the mental ions solutions on the adsorption of Pb2+ was very complicated, to be a combination of inhibition and promotion depending on the metal ions concentration in the solutions, however the adsorption capacities of Cu2+ and Zn2+ ions were decreased with the coexistence of Pb2+ ions.