Study On The Preparation And Adsorption Behavior Of Palladium Selective Adsorbent

Palladium is a very important precious metal,and it is widely used in various industrial fields.Because palladium ions are usually present in industrial wastewater,it is great significance to recover palladium from wastewater.In this paper,nano-silica and polyglycidyl methacrylate microspheres were modified to prepare adsorbents for palladium ion adsorption.Effects of pH,adsorption time,initial Pd(II)concentration,selective adsorption and reuse times on adsorption process were investigated,and the adsorption mechanism was investigated by studying adsorption kinetics and adsorption isotherms.These researches provide a technical reference for the recycling of palladium ions from wastewater,and the main research contents of this paper are as follows:(1)Three new adsorbents were successfully synthesized via functionalizing nanosilica with imidazoline(ELD-SNPs),functionalizing poly glycidyl methacrylate with 8-aminoquinoline(AQ-PGMA)and functionalizing poly glycidyl methacrylate with 1,2,4,5-benzenetetracarboxylic acid(PMDA-PGMA),which were characterized by TEM,FTIR and XPS.(2)Effects of pH,adsorption time and initial Pd(II)concentration on adsorption were investigated.The max adsorption capacity of Pd(II)(ELD-SNPs: 68.2 mg/g;AQPGMA: 266.7 mg/g;PMDA-PGMA: 140.7 mg/g)were achieved when the pH were 4.0,1.0,2.0,adsorption time were 3,1,5 h and initial Pd(II)concentration were 500,700,700 mg/L,respectively.In addition,the ELD-SNPs,AQ-PGMA and PMDA-PGMA demonstrate good regenerative ability and satisfying selectivity for recovery of Pd(II).Compared with ELD-SNPs,AQ-PGMA and PMDA-PGMA,AQ-PGMA has obvious advantages in pH,adsorption time,and saturated adsorption amount of Pd(II).(3)Based on the kinetic analysis of adsorption process of ELD-SNPs,AQ-PGMA and PMDA-PGMA,the adsorption kinetics follow Pseudo-second-order model which indicate that the kinetic restriction of the adsorption process is chemical adsorption.The isotherms adsorption analysis of adsorption process showed that the isotherms adsorption models follow Langmuir and Hill model,which proves that the adsorption process is monolayer chemical adsorption.(4)The results of XPS and SEM-EDS analysis show that the adsorption mechanisms of ELD-SNPs,AQ-PGMA and PMDA-PGMA are dominated by the chelation and ion exchange reactions.It has been confirmed that the adsorption of palladium ions by ELD-SNPs,AQPGMA and PMDA-PGMA is based on chelation and ion exchange.These adsorbents show high adsorption capacity,good selectivity and can be recycled multiple times.This indicated these adsorbents would be effective and promising adsorbents for the recovery of Pd(II)from wastewater.