Synthesis Of Caal-layered Double Hydroxide With Clean Process And Its Applications

CaAl layered double hydroxide(CaAl-LDHs)have been widely attracted as catalysts,absorbent,functional adjuvant materials,biological and medical materials applied in many fields.CaAl-LDHs can also improve cement mechanical properties as concrete addictive.However,complicated traditional synthetic method,the productive process of which produces plenty of waste water,limited the development of application of CaAl-LDHs to some extent.On the other hand,calcium desulphurization is mainly adopted by absorption process of industrial waste gas sulfur dioxide nowadays.Industry generating plenty of sulfur dioxide can produce a large number of by-product desulfurization gypsum,such as thermal power generation and smelting of ferrous metal.In addition,aluminum dross(gibbsite)is facing similar problem.This paper came up with a kind of CaAl-LDHs synthetic method under hydrothermal condition utilizing industrial residues,raw materials of which are desulfurization gypsum,gibbsite and quicklime,respectively.X-ray diffraction(XRD),Fourier transform infrared spectroscopy(FT-IR),scanning electronic microscope(SEM)and inductively coupled plasma spectrum analysis was adopted to characterize synthesized products,which is proved by the result to be a kind of sulfate intercalated lamellar bimetallic compound hydroxide with 10-20?m sized hexagonal sheet morphology.The ratio of Ca2+ and Al3+ is 3:2.In addition,the effect of synthesized CaAl-LDHs as cement additive on paste viscosity,setting time,contractibility and compressive strength was measured by slump tester,concrete penetration resistance meter,Non-contact concrete shrinkage and deformation tester and compression-testing machine,respectively.The experimental results indicate that applicable addition level of CaAl-LDHs can respectively increase slumps of cement samples by 21%,shorten initial setting time by 12%,23%for final setting time,declines shrinking by 50%and 40%at 3 days and 28 days respectively,and increase compressive strength by 7%and 2%at 3 days and 7 days,respectively.Experimental results indicates that CaAl-LDHs could reduce viscosity and shrinking percentage,shorten setting time and promote compressive strength to some extent.At the same time,Mg/AI-LDHs adopted for comparison in the experiment does not show the ability of improving cement properties.In addition,this paper prepared NO3' intercalated CaAl-LDHs with similar synthetic method and investigated its absorptive property of heavy metal ion Cu2+,Cd2+ and Pb2+ in liquor.Experimental results shows that enrichment percentage of Cu2+,Cd2+ and Pb2+ reaches 98%,99%and 30%,respectively,which reveals its application prospect in the field of waste water treatment.