Study On Adsorption And Reduction Of Ag(â… ), Hg(â…¡) And Cr(â…£) Ion By Polyaniline Loaded On Polyurethane Foam

Water is an indispensable material in human life and production . activities, is also an irreplaceable valuable resource. With the rapid development of global economy, the pollution is becoming increasingly worse when people get economic benefits; water pollution by heavy metal ion is particularly outstanding. Both in domestic or abroad many researchers have done a lot of work in heavy metal wastewater treating technology, and made impressive achievements. At present, the report on polyaniline and its composites using for heavy metal wastewater treatment is presented, but polyaniline loaded on polyurethane sponge for this use has not been reported. Polyaniline has special molecular structure; the molecular chain has a rich oxidation and reduction state, part of heavy metal ions can be adsorbed or reduced by polyaniline; polyurethane foam with light weight and large surface area, so the dispersion of polyaniline can be improved. In this paper, polyaniline was loaded on polyurethane foam by in situ chemical oxidative polymerization, and further used to adsorb and reduce Ag(â… ), Cr(â…¥), Hg(â…¡) ions in the solution respectively.This work obtained the following research results:(1) The effect of polyaniline loading amount, pH value in the solution, temperature, concentration of the substrate Ag(â… ) ion, as well as shock or static condition on the adsorption and reduction performance of PAn/PUF composite was investigated. The possible mechanism of adsorption-reduction process was also proposed based on the analysis of its kinetics. The results show that the pH value of the solution is the main factor affecting the reduction process, the loaded amount of polyaniline is the second factor. Silver reduction datas at different concentration were found in accordance with the first order kinetics fitting, it contains two different process rate of first order reaction when the experimental data was analyzed in two time periods. Therefore this process may be a mixed control process, including two consecutive process i.e liquid membrane diffusion process and interface chemical reaction.(2) The effect of preparation condition of PAn/PUF composites, polyaniline loading amount, pH value in the solution, temperature as well as concentration of the substrate Hg(II) ion on the adsorption and reduction performance of PAn/PUF composite was investigated. Reuse effect was also discussed. And the related mechanism was also proposed based on the kinetics and thermodynamics analysis. Finally smelting and battery factory mercury-containing wastewater experiment was simulated. The results show that removal ratio can reach 99.96% when the mass fraction of polyaniline in the polyurethane foam up to 3.67%, the removal effect is better when solution pH value is between 4 and 8. The reuse performance after treating with ascorbic acid is better than the other three kinds of treatment. The process of PAn/PUF composites adsorption and reduction Hg(â…¡) ion as a whole is in accordance with the first order kinetics, including two different rate processes when the experimental data was analyzed at two time periods. The rate from 10 to 60 min is relatively fast,60-720 min is slow. The process may be controlled by physical adsorption and chemical reduction together. Isotherm fitting curve is consistent to Freundlich adsorption isotherm. Thermodynamic data of â–³H-31 kJ-mol-1 shows that this process is an endothermic reaction, higher temperature is beneficial to the reaction, â–³G<0 show that this process is spontaneous, and the higher the temperature the higher the spontaneous degree. Finally simulated wastewater experiment also has a good result. This treatment method can still meet the national industry discharge standard even in the presence of high concentration interference ions.(3) The effect of preparation condition of PAn/PUF composites, polyaniline loading amount, pH value in the solution, temperature as well as concentration of the substrate Cr(VI) ion on the adsorption and reduction performance of PAn/PUF composite was investigated. Reuse effect was discussed. The possible mechanism was also proposed based on the kinetics and thermodynamics analysis. Finally electroplating chromium-containing wastewater experiment was simulated. The results show that removal ratio can reach 99.99% when the mass fraction of polyaniline in the polyurethane foam up to 5.83%, the removal effect is better when solution pH value is between 2 and 7. The composite treated with ascorbic acid still has high removal efficiency after reusing four times. The process of polyaniline loaded on polyurethane foam for removing Cr(VI) ion is in accordance to Ho pseudosecond-order model, so the process may be controlled by chemical adsorption mechanism. Isotherm fitting curve is consistent to Freundlich adsorption isotherm. Thermodynamic data of AH>40 kJ-mol-1 show that this process should contain the rupture of chemical bond. The process of PAn/PUF composites for removing Cr(VI) ion not only includes physical adsorption but also a chemical reduction process. And the experimental effect using simulated. Cr(VI) ion wastewater is also good. This method has the. advantages of simple operation and high removal efficiency in the wastewater treatment process. Therefore the PAn/PUF composite material should have a promising application in wastewater treatment technolgy.