Behavior And Mechanism Of Pb(?) And Cd(?) Adsorption By Hydrous TGD With Different Zeta Potentials

Heavy metal pollution incidents have occurred frequently in recent years,causing constant attention from academic circles and society.The content of heavy metal in surface waters in many regions of China is seriously exceeded.Heavy metals are highly toxic and non-biodegradable,causing long-term damage to the ecological environment and animals and plants.Therefore,it is of great significance to research and develop new and efficient water purification materials and technologies.In this paper,a series of hydrous TGD materials were synthesized by using DGD and FGD.The effects of the concentration of DGD on the structural properties of TGD and mechanism were investigated by SEM,XRD,FT-IR,BET and Zeta potential analysis.Then the factors affecting the adsorption of Pb(?)and Cd(?)by TGD and the methods of TGD regeneration were also studied.At last,the mechanism of adsorption of Pb(?)and Cd(?)by TGD was discussed by macroscopic(adsorption thermodynamics and adsorption kinetics)and microscopic(Zeta potential,FT-IR and XPS)perspective.The conclusions reached are as follows:The concentration of DGD affects the nucleation and growth rate of TGD.The higher concentration of DGD produces TGD structure disorder,more lattice defects,more pores and larger specific surface area,which shows a higher Zeta potential(absolute value),and Better adsorption of heavy metal ions.The Zeta potential of TGD is positively correlated with the adsorption amount q,and the correlation coefficient is as high as 0.99.The adsorption and removal rates of Hb to Pb(?)and Cd(?)increase with the increase of initial concentration and pH of metal ions.It is difficult to remove the adsorbed metal ions with distilled water,and it can be desorbed with dilute hydrochloric acid or added with a new TGD to increase the number of recycling.The adsorption process of Pb(?)and Cd(?)by TGD has the best effect by Langmuir adsorption model and pseudo-secondary dynamic model.Adsorption is an endothermic and spontaneous process.The higher the Zeta potential,the faster the adsorption rate and the better the adsorption.The experimental results show that the active sites on the surface of TGD are evenly distributed.The adsorption of Pb(?)and Cd(?)on the surface of TGD is monolayer and uniform.After the adsorption of metal ions,the Zeta potential decreases,and the metal ions form an inner layer with the surface hydroxyl groups of TGDs.And form a Pb-O or Cd-O bond.