| Montmorillonite(Mt)has lamellar structure,excellent cation exchange capacity,negatively charged lamellar surface,and excellent specific surface area,etc.It has good adsorption performance for organic pollutants and heavy metal ions,and has an important application prospect in the field of sewage treatment.And because Mt has good gel properties,it is difficult to separate from the water body in the sewage treatment process,which limits its wide application in sewage treatment.In order to solve this problem,this paper took Liaoning caszo sodium Mt and polyvinyl alcohol as raw materials,formaldehyde as cross-linking agent,concentrated hydrochloric acid as catalyst,using wet method and semi-dry method to prepare polyvinyl formaldehyde-montmorillonite composite particles(PVAM-Mt)with easy separation and better adsorption performance than Mt.Using X-ray diffraction(XRD),scanning electron microscopy(SEM),infrared spectroscopy(FTIR),Zeta potential,specific surface area test(BET)and loss rate(ω)testing methods,the polyvinyl formal(PVAM)mesh was studied.The influence factors of bag density,the influence of preparation methods,technology and process conditions on the structure,morphology and physical and chemical properties of PVAM-Mt are studied;On this basis,the separation effect of Mt and PVAM-Mt from water and the removal effect of organic pollutants and heavy metal ions were compared and studied.The adsorption capacity and mechanism of PVAM-Mt prepared by semi-dry method for methylene blue and Pb2+ were studied.The wet PVAM-Mt prepared by wet and semi-dry methods still maintained the layered structure of Mt,and the d001 value of the wet PVAM-Mt was 1.52 nm and 1.94 nm,respectively,which was equal to or greater than the d001 value of the wet Mt(1.50 nm).Wet and semi-dry PVAM-Mt particle size expansion ratios can reach 2 times and 1.73 times,respectively,with good water swellability;the density of polyvinyl formal mesh bags increases with the increase of crosslinking degree;PVAM-Mt has more pores and grooves;the zeta potentials of wet and semi-dry PVAM-Mt are about-23.8 m V and-20.2 m V,respectively,and the absolute values of the zeta potentials of PVAM-Mt obtained by wet and semi-dry methods are both Slightly lower than Mt(-24.5 m V),but the difference is not much,the original Zeta potential of Mt is basically retained;when the amount of formaldehyde is 5.3 mmol/g,PVAM: Mt=0.15,the loss after wet PVAM-Mt treatment of sewage The rate is 1.68 %,and the loss rate of semi-dry PVAM-0.4-Mt-0.15 is only 0.45 %.The mechanical strength of semi-dry PVAM-Mt is obviously better than that of wet method,so PVAM-Mt has low water loss and high strength.The removal rates of Mt for methylene blue and lead ions reached 93.40% and 91.00%,respectively.The removal rates of wet PVAM-Mt for methylene blue and Pb2+ reached 97.80% and 94.40%,respectively,which were better than Mt.The semi-dry PVAM-Mt was even better than wet method.The semi-dry sample PVAM-0.4-Mt-0.15 was selected for adsorption capacity study,and its adsorption capacity for methylene blue and Pb2+ reached 60.14 mg/g and 62.47 mg/g,respectively.The adsorption capacity of PVAM-0.4-Mt-0.15 for methylene blue and Pb2+ is higher than the adsorption capacity of Mt raw materials given in the literature.Therefore,the adsorption performance of PVAM-Mt for methylene blue and Pb2+ is better than that of Mt raw materials.The main contribution of PVAM-Mt to the adsorption of methylene blue and Pb2+ comes from the electronegativity of the Mt sheet,the Al hydroxyl group on the Mt end face,the PVAM hydroxyl group and the oxygen atom on the ether bond.In addition,PVAM in PVAM-Mt also contributes to the entanglement of methylene blue. |
