Study On The Adsorption Performance Of New Chloromethyl Polystyrene Resin For Palladium

In the separation of platinum group metals,absorption has attracted wide attention because of its many advantages compared with the traditional extraction methods such as precipitation and solvent extraction.The advantages of adsorption are high enrichment factor,high selectivity,less chemical reagents,and it is environmental friendly.In this paper,chloromethylated polystyrene was used as a carrier and a new-type graft polymer adsorbent was synthesized and used in the extraction and separation of palladium from leaching solution of a secondary resource.The prepared polymers were compared with impregnated resin and the adsorption material has very high stability.When these materials are compared with inorganic materials such as activated carbon,graphene oxide,carbon fiber,carbon nanotubes,and nano-metal oxides,they have better selectivity.And when,compared with the biological adsorbents,the prepared polymers have better acid and alkaline resistance.By means of chemical synthesis,heterocyclic compounds containing multiple nitrogen and sulfur atoms were grafted onto the chloromethylated polystyrene matrix.This paper synthesizes four kinds novel resin adsorbents,respectively as 2-p-Tolyl sulfanyl-4,5-dihydro-thiazole(TDT),2-(p-tolylthio)benzo[d]thiazole(TBT),2-methy-5-(p-tolylthio)-1,3,4-thiadiazole(MTD),and 4-methyl-3-(p-tolylthio)-4H-1,2,4-triazole(MTT).SEM,XPS,IR,BET,and other techniques were employed to characterize the prepared adsorbents.The optimum adsorption and elution parameters,such as pH value,contact time,maximum adsorption capacity,distribution ratio,and elution concentration were obtained through experimentation.The results showed that in the medium of hydrochloric acid from 0.1 to 1 M,the four adsorbents have good adsorption performance on Pd(?),and have a maximum adsorption capacity of qm>100 mg/g.Thermodynamic and kinetic studies showed that the four adsorption systems were?H?>40 kJ/mol,?G?<0 kJ/mol,the adsorption behavior was a spontaneous endothermic reaction,the adsorption isotherm agreed with the Langmuir model,the adsorption kinetics obeyed a the pseudo-second order expression,and the adsorption behavior of chemical adsorption was a single molecular layer.The prepared systems eluted Pd(?)with acidic thiourea with a stripping rate of more than 96.0%and when repeated three times and the recovery was more than 94.0%.The study on the separation of automobile waste leachate showed separation coefficients for ?(Dpd/DM)of Pd(?)and Pt(?),Rh(?),Cu(?),Fe(?),and Ni(?)>103.The separation of Pd(?)from coexisting ions Pt(?),Rh(?),Cu(?),Fe(?)and Ni(?)was achieved.The mechanism of separation was modeled with a Gaussian09 program and the possible geometrical structures of palladium complexes were studied with density functional theory(DFT).The theoretical infrared spectra of possible structures were combined with experimental IR and XPS data.Overall,the adsorption mechanism of Pd(?)on polystyrene resin was predicted.