Complexation Effect And Mechanism Of Palygorskite Colloids On Heavy Metals

In recent years,various methods and technologies have been applied to the treatment of heavy metal wastewater,in which the complex-ultrafiltration coupling process has developed rapidly,and the choice of complexing agent is the most important factor for the function of this technology.The colloidal palygorskite can effectively adsorb heavy metal ions in the water through complexation,which can replace the traditional organic complexing agent and play a certain role in promoting the application of complexation-ultrafiltration coupling technology.This experiment attempts to use the purified and rod-dissociation palygorskite nanoparticles instead of surfactants and high polymer complexing agents.Through static ultrafiltration experiments,the main influencing factors and kinetics of the heavy metal ions adsorption on the palygorskite are studied to determine the best conditions for the purification of the palygorskite and the adsorption process parameters.The XRD pattern of the palygorskite clay after purification with different concentrations of H₂SO₄ and HCl shows that there are certain changes in the characteristic peaks of each mineral.Palpeocene characteristic peaks show a tendency of increasing first and then weakening.With the increase of acid concentration,palygorskite will change to a new mineral,but it will eventually become quartz.Treating palygorskite with an appropriate concentration of acid and dispersant can significantly improve the purification effect and colloidal stability of palygorskite,which is beneficial to the industrial application of palygorskite clay.When palygorskite is treated with a low concentration of acid,the impurities are not completely dissolved and the purification effect is poor.When palygorskite is treated with a high concentration of acid,the crystal structure of palygorskite is destroyed and converted to quartz and other minerals,affecting the purification effect of palygorskite.When the use of sulfuric acid with a mass fraction of 5% and sodium hexametaphosphate with 4%,the purification effect is best,and the purity of the palygorskite can be increased to 85.34%.When using a mass fraction of 15% sulfuric acid and 3% sodium hexametaphosphate to treat the palygorskite clay,the zeta potential of the palygorskite colloid reaches the lowest and the colloid is the most stable.Copper ions are complexation with different Colloidal which prepared by different solidliquid ratios,when the concentration of Cu²⁺ in wastewater is low（10⁶0 mg/L）,the removal of heavy metals is above 95%.When the concentration of Cu²⁺ in waste water was 80 and 100 mg/L,the interception rate of heavy metals showed a significant increase along with the decrease of solid-liquid ratio.At the dispersion solid-liquid ratio of 1:50,the Cu²⁺ removal rate reached 92.02% and 84.85%,respectively,and the lower the solid-liquid ratio,the more fully dispersed the palygorskite rod crystal structure.Several different dispersion processes have good effects on low-concentration wastewater treatment,but there are certain differences in high-concentration wastewater.Complexing effect of Cu²⁺ when colloidal prepared using the high-speed stirring-ultrasonic combined dispersion process was slightly better than that of colloids prepared by high-speed stirring alone,which was significantly better than that of colloids prepared by ultrasonic alone.From the economical point of view,the palygorskite colloids prepared at a solid-liquid ratio of 1:20,11000 rad/min for 15 min are most suitable.Wastewater containing Cu²⁺ and Pb²⁺ was treated with different loading ratios.Cu²⁺ and Pb²⁺ removal rates decreased significantly with the change of loading ratio.The Cu²⁺ removal rate gradually dropped from the highest 99.02% to 51.68%,and the Pb²⁺ removal rate gradually decreased from the highest 99.86% to 24.69%.From the kinetic analysis of heavy metal ion-palygorskite colloidal complexation reaction,under the conditions of the initial concentration of 100 mg/L,Cu²⁺ and Pb²⁺ reach the complexation equilibrium time of 90 and 120 min,respectively.The complex reaction of palygorskite with two heavy metal ions can be described by a pseudo first-order rate equation.When the initial concentration of heavy metal wastewater was 40 mg/L,the “critical loading ratio” of Cu²⁺ and Pb²⁺ measured was 1:30 and 1:40,respectively,and the complex capacity of the palygorskite colloids for Cu²⁺ and Pb²⁺ is 0.024 and 0.033 g heavy metal ions/g palygorskite,respectively.