Study On Correlation Between Particle Size Distribution Of Aged Refuse And Environmental Chemical Behavior Of Heavy Metal (Cu²⁺) In Aged Refuse

Nowadays, with the rapid urbanization of our country, the production of municipal solid waste (MSW) has been increasing. Due to the high moisture content and low heat value of MSW, sanitary landfill has still been the main treatment of it. Huge pressure from the economy and society will be faced by the new landfill site, because of the rapid development of economy and public awareness. Therefore, increasing the current capacity of the landfill and prolonging the service life of the old landfill have been the effective method to release the pressure of landfill in our country. What's more, the utilization of aged refuse resource is the key to this method.Aged refuse included dissolved organic carbon compounds and nutrient composition for plant growth. The researchers both domestic and international used it for vegetated soil and designing bio-filters for treating landfill leachate and various wastewaters, but aged refuse contains heavy metals, the factors such as particle size distribution disordered that it was a obstacles in cyclic utilization of aged refuse. Our lab in early research found that the particle size distribution of aged refuse appears polarization trend.We also found that the content of soluble-salt and the damage to plant negatively correlated with the particle size.Therefore, because of the aged refuse contain more heavy metal which will cause the environmental risks at its resources, so it became the focus of attention on cyclic utilization of aged refuse. The particle size distribution disordered of aged refuse may influence the environmental risks. This paper studied on the correlation between particle size distribution of aged refuse and environmental chemical behavior of heavy metal in aged refuse. It implicate that the environmental chemical behavior of different particle size aged refuse was different to each other in content of heavy metal. We select the smaller risk particle size at environment in order to provide basis theoretical for aged refuse in safe and effective utilization.The adsorption and desorption effect of aged refuse of various particle-size on Cu2+ and possible environmental hazards exerted by Cu2+ under different states in different particle-size of aged refuse was investigated.Cu2+ adsorption kinetics showed that adsorption rate and adsorption of aged refuse with size of 900-300μm (maximum diameter) was significantly lower than the smaller particle size. Its dynamic model, Elovich model and the two-constant rate model fit each other. The adsorption behavior of aged refuse is not a homogeneous diffusion process but is influenced by the diffusion rate and spreading factor.The adsorption isotherms of Cu2+ showed that the adsorption capacity of aged-refuse on Cu2+ has the negative correlation with its particle size in a certain concentration. The aged refuse with the particle size of 900-300, 300-150,105-90,900-0μm followed Freundlich model, and the model parameters suggested that the adsorption capacity is negative correlated with particle size. The other particle size of aged refuse fit Langmuir model.Adsorption thermodynamics showed that the adsorption was spontaneous, entropy, endothermic process. The thermal entropy value needed by aged refuse with large size was lower than the small particle size; on the other hand, the large size of aged refuse has the lower adsorption activity on Cu2+, while the smaller size is just opposite.Whether adsorption of Cu2+ by the aged refuse was influenced by pH was studied and the data showed that pH at lower levels could affect the adsorption capacity, while the mainly capacity of adsorption was the precipitation at higher levels, and the best adsorption conditions were pH 7.Desorption experiment showed that Cu2+ adsorbed by the aged refuse existed in ion-exchange multi-state form, and the adsorption rate more rapid, larger amount desorbed.The examinations of the content of different forms of copper showed that water soluble and ion exchangeable copper was not detected, while the content of organic matter speciation was the highest, and carbonate speciation content was the least. Different size showed differences in their content. The content of different speciation of heavy metal is negative correlated with particle size.