The Preparation Of Borate Intercalated Magnesium-aluminum Hydrotalcite Hierarchical Porous Material And Its Adsorption Performance

The pollution of water by organic dyes in industrial wastewater such as paper making,printing and dyeing,has attracted worldwide attention.Many dyes are biotoxic and carcinogenic.Organic dyes are often difficult to be biodegraded and removed due to their complex structures and characteristics.The adsorption method is considered to be a preferred method for removing organic dyes because of its simple operation,high efficiency,low cost,and recyclability of the adsorbent.The layered double hydroxide has a unique ordered layer structure,a large specific surface area,an anion exchange between the layers and a large interlayer anion capacity.The structure of borate anion is various and its thermal stability is high,which makes the borate has a great development prospect in the fields of flame retardant,luminescence and sewage treatment.By inserting borate anions as a guest anions into the hydrotalcite interlayer,a multi-stage pore structure may be formed,which can significantly enlarge the surface area of the material,so that the hydrotalcite-like material of the borate intercalation layer has better adsorption capacity,thereby enhancing the adsorption application value.Therefore,it is of great significance to design and synthesize polyborate intercalated magnesium aluminum hydrotalcite multi-stage pore materials and study their adsorption properties.In this paper,the borate anions intercalated MgAl-hydrotalcite(LDH)material with hierarchical porous and the GO supported borate anions intercalated MgAl-LDH material have been prepared by precursor method and hydrothermal method respectively.The XRD,FT-IR,XPS,SEM,TEM,BET and BET were used to characterize the phase structures and morphologies of the samples.The related adsorption properties were also studied.(1)Using calcined MgAl-LDH as precursor(MgAl-LDO),a hierarchical porous B-LDHs material with borate anion intercalated was synthesized by immersion in borax solution.Then hierarchical porous B-LDOs microspheres were prepared by calcinated of B-LDHs sample.Several grounps of controlled experiments were carried out to investigate the effects of reaction ratio,temperature and time on the morphology of the synthetic sample B-LDHs.The specific surface areas of the B-LDHs and the calcined B-LDOs microspheres were measured as 138.6 and 123.0 m2/g,respectively.The adsorption performances of two samples to Congo red solutions were studied.The maximum adsorption amount reached 166.39 mg/g and 273.22 mg/g,respectively.The adsorption processes of both were fitted with the pseudo-secondary kinetic model and the Langmuir adsorption model.B-LDOs sample has higher adsorption efficiency,good cycleability and stability,making it more suitable for wastewater treatment applications.(2)Borate anions intercalated hydrotalcite-like materials(UB-LDHs)with multi-stage pore structure were synthesized under hydrothermal conditions by adding urea and ammonium pentaborate to the magnesium-aluminum salt as raw materials.Several grounps of controlled experiments were carried out to investigate the effects of reaction ratio,temperature and time on the morphology of the synthetic sample UB-LDHs.The adsorption performance of UB-LDHs on Congo red was studied on the basis of characterization.The adsorption behavior was fitted with the pseudo-second kinetic model and the Langmuir adsorption model.The maximum adsorption capacity for Congo red were reached 383.14 mg/g,showing excellent adsorption ability.The UB-LDHs after calcination showed an amorphous state,but the spherical shape of the flower was basically maintained by scanning the image.The adsorption properties for CR were studied.The results showed that when the concentration of CR solution was lower than 450mg/L,the removal rate could reach more than 99%.Therefore,this new hierarchical porous borate intercalated hydrotalcite material and its calcined products are can be used as a promising green and low-cost adsorbent for wastewater treatment.(3)A hydrothermal method was used to synthesize a layered ordered structure of GO supported borate intercalated hydrotalcite-like material(GO/UB-LDHs).The selective adsorption of different dyes on the prepared composite was studied,in which its adsorption efficiency to methylene blue and Congo red was better.The effect of the amount of composite on the adsorption of methylene blue MB was also studied,and the optimum dosage was determined to be 5 mg.The adsorption behavior of GO/UB-LDHs to MB is fitted with the pseudo-secondary kinetic model and the Langmuir adsorption model,and the maximum adsorption capacity is 454.55 mg/g.This composite material is simple and easy to prepare,which has good adsorption capacity for methylene blue.Therefore,GO/UB-LDHs can be expected to be applied to organic dye wastewater treatment.