Study On Treatment Of Pyrophosphate Copper Plating Wastewater By Synthesizing LDH In Situ

Based on the principle of synthesizing layer double hydroxide,the research was to investigate the efficiency and impacting factors of removing anions containing P from pyrophosphate copper plating wastewater by layer double hydroxide synthesized in situ,also to find the preferable disposing conditions.The chemical analysis instruments such as XRD,FT-IR and TEM were adopted to discusse the mechanism of disposing the plating wastewater by layer double hydroxide synthesized in situ.In the same time,thermodynamics and kinetic study was conducted on the adsorption of orthophosphate anions on Layer Double Hydroxide(LDH).The results show as follow:The influence of pH value is remarkable,when pH is in the range of 8 to 10, the removal efficiency of anions containing P is high,all above 80%,the range is wide.When the initial concentration is 100 mg/L,the removal efficiency of anions containing P is the highest,all above 97%.The initial concentration is lower,the removal efficiency is higher.The influence of Mg/Al ratio is small.When Mg²⁺/Al³⁺ratio is 3:1,the removal efficiency of anions containing P is the highest. When the concentration of Mg²⁺and Al³⁺is 70.4 mg/L and 211.2 mg/L respectively, the remnant concentration of TP is 0.415 mg/L,achieved the first-class discharge standard(GB 8978-1996).The outcomes was approved to be layer double hydroxide by XRD,FT-IR and TEM analysis.The arrangement mode of PO₄^3-in the interlayer of LDH was slantwise double layer,the angle tilted was 39°,the arrangement mode of P₂O₇^4-in it is slantwise monolayer,the angle tilted was 45°,the arrangement mode of[Cu(P₂O₇)₂]^7-is lateral monolayer.The enthalpy change of the adsorption of orthophosphate anions on LDH(ΔH)is 7.96 kJ/mol,the entropy change(ΔS)is 33.59 J/K·mol,and the energy change(ΔG) is in the range of-1.71～-3.06 kJ/mol,it shows that the adsorption progress is a spontaneous endothermic and an increasing entropy process,the adsorption progress contains both of chemical sorption and physical sorption.The adsorption activation energy is 8.3 kJ·mol^-1,it shows that the influence of temperature is small, and the adsorption progress is controlled by physical adsorption-film diffusion.