Nano hydroxyapatite stable suspension system:Preparation and cobalt adsorption performance
To improve the adsorption performance of nano-hydroxyapatite(HAP)as a heavy metal ion adsorbent,the polymer-induced liquid-like precursor mineralization process in the human body was simulated.A stable suspended nano HAP system was prepared by hydrothermal method using polyacrylic acid(PAA)as a regulator.The effects of R(the ratio of the amount of substance of COOH in PAA to Ca),reaction pH,and hydrothermal temperature on the prepared nano HAP were investigated.The optimized synthesis conditions for nano HAP were R=1,pH=9.00,180 ℃,which is a spindle-shaped structure composed of small particles and stably suspended while maintaining several tens of nanoparticle sizes.Subsequently,the effects of adsorption time,initial metal ion concentration,pH of adsorption environment,and suspension on the Co2+adsorption performance of nano HAP were investigated.The adsorption results indicate that the adsorption kinetics follow a pseudo-second-order kinetic model,and the adsorp-tion process includes surface adsorption and intra-particle diffusion.The linear equation fitting results of the Freun-dlich and Langmuir models had a high degree of agreement with the experimental results.The adsorption belongs to the chemical adsorption of non-uniform adsorbents,and the linear fitting result of the Langmuir model correspond-ing to the maximum adsorption amount was 229.358 mg·g-1.The removal rate of Co2+increased with the increase of adsorption environment pH(6.48-9.00),and the main adsorption mechanism was surface coordination reaction.The adsorption capacity of the prepared nano HAP suspension was significantly better than that of the non-suspended control nano HAP.The addition of PAA enhances the adsorption capacity of nano HAP.
nano hydroxyapatitepolyacrylic acidadsorptioncobalt ion
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