Anti-acid Absorbing Cadmium Three-dimensional Network Materials: Preparation And Application

The acidic environment affects the adsorption of cadmium on common materials,making the treatment of cadmium pollution even more problematic.Therefore,it is great significance to develop new materials that adsorb cadmium in an acidic environment.In this paper,the three-dimensional network structure was incorporated with some materials with strong acid resistance as novel adsorbent.The novel absorbent would be singned with two meirts.On the one hand,the whole acid-resistance properties were enhanced,on the other hand,the contact area between the acid-resistant material and the cadmium ion is increased by dispersity effect of the three-dimensional network structure.Based on this,two new inorganic-organic/organic-organic composites were prepared,namely MoS₄-LDH-PP?LDHS-PP?and fulvic acid-PP?FA-PP?.The main results would be described in sequence section:The surface of the bulk polyacrylamide/sodium acrylate hydrogel incorporated with layered hydrotalcite MoS₄-LDH was greatly enhanced.The prepared LDHS-PP materials are interlaced or overlapped with an irregular lamellar three-dimensional network structure.The pores are abundant,and a large amount of molybdenum and sulfur are present on the LDHS-PP polymer organics.In the XRD spectrum,PP has no diffraction peaks,and there are multiple characteristic diffraction peaks of MoS₄-LDH with different intensities in LDHS-PP.The experimental results show that the effect of LDHS-PP on adsorption of cadmium under weakly acidic conditions is significantly higher than that of PP.When the pH was 3,the removal rate of PP was 0,while the removal rates of 0.5%,1%,and 2%of LDHS-PP were 21.33%,45.6%,and 24.60%,respectively,and the 1%LDHS-PP has the best performance of acid adsorption.Sips model showed that the adsorption capacity of LDHS-PP was higher than that of PP?1893.09 mg/g?,and the adsorption capacity of 1%LDHS-PP?2789.58 mg/g?was the highest.The adsorption of Cd?II?on LDHS-PP materials reached equilibrium around 60 to 90 min and met the pseudo-first and pseudo-second kinetic models.With the increase of sodium ion concentration,the removal effect of cadmium on materials has been reduced to varying degrees.When the sodium ion concentration was increased to 100 mM,2%LDHS-PP had better anti-sodium salt interference than the other two,and the removal efficiency was 42.64%.In the XPS spectrum,the change of sulfur content before and after adsorption of cadmium on LDHS-PP material was analysed,and the strong binding between adsorbent and Cd was attributed to that a large amount of MoS₃ could react with Cd to form CdS.The hydrogel PP surface after the incorporation of fulvic acid becomes rough.The FTIR spectra showed that there was hardly any new functional groups in the PP after addition of fulvic acid,but the number of original functional groups increased significantly,which could improve the adsorption performance of FA-PP composites.The adsorption efficiency of FA-PP under weak acidic condition was good.When pH was 4.0,the removal rate of PP was36.70%,while the removal rates of 1%,2%,3%and 4%of FA-PP were 62.30%,67.00%,75.17%and 65.84%,respectively.And the 3%FA-PP has the best anti-acid adsorption performance.The adsorption capacity of the Sips model fitted to FA-PP was higher than that of PP,and the adsorption capacity of 3%FA-PP?4656.25 mg/g?was the highest.The adsorption of Cd?II?on FA-PP materials mainly occurred in the first 20 min and reached the equilibrium state almost at the same time.R² was higher than 0.95,indicating that the pseudo-first order model and the pseudo-second order model met the adsorption kinetics process.With the increase of salt ion concentration,the removal effect of cadmium ions was affected to varying degrees.3%FA-PP had the strongest anti-interference ability to sodium ions among them.When the sodium ion concentration was to 100 mM,the removal effect remained more than 50%.The content of different functional groups with oxygen of FA-PP before and after adsorption of Cd was compared,and the content of functional groups C=O and–COOR were decreased significantly after adsorption of Cd.It is attributed to that the fulvic hydrogel can effectively complex with Cd by some–COO^-,even in acid environment.Consequently,the doping of MoS₄-LDH and fulvic acid to the three-dimensional network-like material not only increases the contact area for heavy metal anion,but also improves the acid-resistant adsorption performance of the materials.It provides new materials to remediate acidic wastewater or acidic soils polluted with heavy metal cadmium.