Transformation Of Alum Sludge Into Aluminum Hydroxide And Layered Double Hydroxides And Their Adsorption

Alum mines and the ’waste’ in the equal distribution of wealth potassium,aluminum and other elements can be used,is a potential can be developed and comprehensive utilization of mineral resources.So far most of such residuals have been viewed as solid waste and thereby are discarded.Consequently,alum production is regarded as a much lower efficient process with the large consumption of natural alunite resources.Moreover,the discarded alum sludge becomes the environmental,ecological and geological hazards.The proper use of alum sludge turns to be a critical issue in alum production.This paper to solve the problem of low value-added of alumina slurry for the purpose of the proposed pulp with alum aluminum hydroxide nano-materials and layered double hydroxides.The structure of the materials were characterized by using modern physical and chemical techniques,such as X-ray diffraction(XRD),Fourier transformation infra-red spectra(FT-IR),Thermal analyses(TG-DTA)and Scanning electron micrograph(SEM).Alum slurry was used as aluminum source to preparation LDHs,and the adsorption properties of calcined LDHs was investigated.Acid-melting and alkaline leaching methods were used to synthesis of Al(OH)3 materials,compared with the two different materials,both methods can prepare Al(OH)3.In addition,the bayerite[α-Al(OH)3]obtained by the acid-melting method while the boemhite(γ-AlOOH)obtained by the alkaline leaching method.That were consistented with those reported,that during the precipitation acidic condition and a neutral condition are favorable for the formation of amorphous aluminum hydroxide and boehmite phases,while under alkaline conditions,the bayerite formation is favored.Mg-Al-LDH,LDH-D,LDH-M and LDH-L have been synthesized by the traditional constant pH value preparation.High crystallinity and well-defined hexagonal shapes LDHs were synthesized from aluminium precursors.Those were confirmed by XRD and FT-IR characterization technology.The particle size is 50～120 nm,and the shape appearance for the sheet.The possible reactions contributing to the LDHs formation can be envisaged.The adsorpions of Acid Red G(ARG)on the synthesized products were intestigated in detail.The factors,such as the concentrations of ARG,additive amount of the products,pH of solution and adsorb time were studied.The results showed that adsorbed ARG increased gradually with the increase of concentration of the ARG.Adsorption was steady at pH=10.Suggested reaction mechanism is due to calcined product of the ’memory effect’ can be ARG adsorbed layer,in order to achieve well adsorption treatment of waste water.The LDO,LDO-D,LDO-M and LDO-L regenerated were used three times and the removal rate of the ARG was still above 60%,which showed reusable and well performance.