Development Of Composite Adsorbents To Remove Low Concentration Of Phosphorus In Water

With the human activities become more frequent and urbanization accelerates,eutrophication of water bodies has become one of the major environmental problems plaguing the world.Once the water body becomes eutrophication,it will not only cause lasting harm to the ecological environment,but also cause immeasurable social and economic losses.At present metal oxides are the most important materials for removal of phosphorus in water,while most of these materials are existed as powder particles with nano-or micron-sizes.When they are implemented in water,they can not settle down easily and might encounter difficult separation and recovery from water.Therefore,it has become the hotspot in this field to realize the easy separation of highly efficient adsorbent material from water,which has great significance to improve the practical application of the powder material.This research targets active alumina powder as an adsorbent for removal of phosphor and by using polyvinyl alcohol?PVA?as a support and calcium alginate?CA?as a clad to realize the modification of alumina powder.The removal behaviors of phosphor in water were investigated.The major research results obtained are summarized as following:the preparation of bulky Al₂O₃/PVA porous composite and removal of PO₄^3-,the preparation of insoluble Al₂O₃/CA composite and removal of PO₄^3-,removing PO₄^3-from aqueous by using insoluble Al₂O₃/CA composite in the fixed-bed column.The principal results obtained are as following:1.The active alumina and PVA were mixed uniformly by heating,and further crosslinked and freeze dried to obtain Al₂O₃/PVA porous composite.The results of batch adsorption showed that the adsorption was consistent with Freundich isothermal and pseudo-second-order model.Meanwhile the composite material could be separated easily and recovered well.When the Al₂O₃ loading rate was 60%and pH of solution was 4,the highest adsorption capacity with 95%was obtained for the 2.5ppm PO₄^3-in water.In addition,CO₃^2-had a great effect on PO₄^3-removal,while the pH value of system had slight effects on it.Experiments showed that the composite has great potential and advantages in the treatment of waste water.This study also provided excellent references to explore the practical application of metal oxides in wastewater treatment.2.By coating a layer of calcium alginate gel on the surface of active alumina powder,the water-insoluble Al2O3/CA composite material was obtained,and the material was easily separated and recovered from the water.After coated with calcium alginate,the BET specific surface area of Al₂O₃/CA was 51.73 m²/g,which was 38.6%higher than original active alumina powder.Adsorption performance was excellent in the pH range of 2-10 and was suitable for pH under natural conditions.The results of batch adsorption showed that the adsorption was consistent with pseudo-second-order model and the adsorption isotherms at different initial concentrations and temperatures are more consistent with the Freundich isothermal.The maximum adsorption capacity of PO₄^3-with Al₂O₃/CA was obtained by calculating with Langmuir isothermal model being 10.31 mg/g.What's more,CO₃^2-had a great effect on PO₄^3-removal.Compared with the original Al₂O₃ powder,the Al2O3/CA composite material has a great improvement both in the characterization and the performance test results,which has potentially practical application.3.The optimal conditions for Al₂O₃/CA dynamic adsorption of PO₄^3-were low concentration,low influent flow rate and high bed height.The optimal ratio of Al₂O₃/CA composite was 1:17.The maximum dynamic adsorption of Al₂O₃/CA for phosphorus was estimated to be 12.95 mg/g.The results show that Thomas model and Yoon-Nelson model can describe the dynamic adsorption behavior of PO₄^3-by Al2O3/CA well.This provides a certain reference value for the realization of industrialization and engineering application.