Preparation Of PANI/LDOs Composites And Their Adsorption Properties For Cr(?) In Water

With the rapid development of electroplating,mining,printing,metallurgy and other industries,a large amount of Cr(VI)-containing wastewater has been discharged into surface water or groundwater.Due to the high toxicity,high fluidity,carcinogenicity and mutagenicity of Cr(VI)to organisms,it has caused serious harm to human beings and the ecological environment.At present,the adsorption method is a common technology for removing Cr(VI)from wastewater.Layered double oxides(LDOs)materials have large specific surface area and high stability,and polyaniline(PANI)has abundant nitrogen-containing functional groups,which offer a great amount of active sites for the capture of pollutants.Therefore,the PANI/LDOs organic-inorganic hybrid materials were prepared by simple hydrothermal calcination and in situ oxidation polymerization,aiming to study the adsorption performance and mechanism of PANI/LDOs for Cr(VI)were studied.The major research is as follows:(1)The characterization results of PANI/LDOs showed that the composites were successfully synthesized.The addition of LDOs reduced the bulk density of PANI,increased the surface area and pore size of the materials,and provided more active sites for the removal of pollutants.(2)The adsorption experiments of Cr(VI)by PANI/LDOs showed that the p H value of the solution had a significant effect on the removal rate,and the adsorption efficiency was the best when p H=2.0;the removal reaction was well fitted by the pseudo-second-order model,which reflects the chemical adsorption process of Cr(VI)on PANI/LDOs.The adsorption isotherm and thermodynamic study showed that the adsorption reaction conforms to Langmuir model,and the adsorption was monolayer-molecular adsorption.When p H=2.0 and T=293 K,the maximum adsorption quantity of Cr(VI)was 409.77 mg/g,and the adsorption reaction was a spontaneous endothermic process.(3)PANI/LDOs composites have good stability,can be regenerated and reused many times without significantly reducing its removal rate.Various co-existing anions in the solution had no significant effect on the adsorption performance,and had a good removal rate on Cr(VI)in simulated real water.(4)The XPS and FTIR analysis of the samples before and after the reaction shows that the adsorption mechanism of Cr(VI)by PANI/LDOs mainly includes the combined action of strong electrostatic attraction reduction and chelation.Under acidic conditions,negatively charged Cr(VI)anions are adsorbed to the surface of PANI/LDOs by protonated adsorbent through electrostatic interaction,and the captured Cr(VI)ions are partially reduced to Cr(III)with low toxicity,and then Cr(III)is bound to nitrogen or oxygen-containing functional groups through chelation,and finally fixed on the surface of the adsorbent.