SELENYUM BASKILI MİKROPARTİKÜL SENTEZİ VE KARAKTERİZASYONU
AKTÜRK, AYSUN EDA
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In this study, the synthesis of selenium imprinted particles to be used as solid phase extraction adsorbent was aimed. The polymeric material in monolith form synthesized by in-situ polymerization was crushed into particles. The synthesis of particles consists of the stages of pre-complex synthesis and polymerization process. The main interaction between template ion and printed polymeric material is metal ion mediated coordinative bond formation. For pre-complex(MAA)-Fe3+, methacrylic acid as functional monomer and SeO42- as template ion were used. The appropriate component ratios for pre-complex were determined by UV-Vis spectrophotometer. Pre-complex, mixed with (EtOH)/acetonitryl solvent /porogen, (EGDMA) ethylene glycol dimethacrylate crosslinker, and (HEMA) 2hydroxyethyl methacrylate comonomer including (AIBN) azo (bis) isobutyronitrile was subjected to polymerization at 80 °C for 3h in a constant temperature bath. Then, the target ion was removed by methanol: acetic acid washing solution and imprinted particles (SIM1, SIM-2, SIM-3) were obtained. The same recipe was administered without target ions and the non-imprinted particles (SNIM) were synthesized. The particle size used in the iv studies was in the range of 5-67 μm. The synthesized particles were characterized by SEMEDX, BET, FTIR and TGA. The surface area of 180.9 m2/g for the non-imprinted particles increased to 193.5 m2/g for the imprinted particles and it was determined that the existing pore type conformed to the mesopore definition. Selenate ion adsorption was investigated in batch mode with imprinted and non-imprinted particles. Selenate ion concentrations were determined by ICP-MS. The effect of parameters such as pH, initial concentration, temperature, ionic strength, interaction period on adsorption capacity were investigated. pH: 3.0, temperature: 25.00C, interaction time :100 minutes and concentration :500 ppm were determined as the optimum values. Maximum adsorption capacity under these conditions was 133.7 mg SeO42-/g polymer for SIM-2 coded printed particles. For adsorption studies carried out at different temperatures, Langmuir, Freundlich, Temkin adsorption isotherm models were applied and it was found that Langmuir model was the most suitable model for adsorption data. Thermodynamic quantities such as enthalpy change, entropy change, Gibbs free energy change were calculated for the adsorption process. Kinetic analysis proved that the adsorption followed pseudo 2nd-order model without any diffusion restriction. In reusability tests, the decrease in adsorption capacity was 12%, following the consequent 10 adsorption-desorption cycles. The selectivity of particles for selenate was proved by analyzing the tap water sample spiked with SO42-, PO43-, Cl-, Br- AsO43- and NO3- anions by ion chromatography and by ICP-MS for arsenate and selenate ions.