Studies On Magnetic Microsphere Extraction For Spectrophotometric Determination Of Chromium(?,?) And Lead(?)

This study mainly focused on determination of Chromium(III, VI) and Lead(II) by magnetic microsphere extraction coupled with spectrophotometric determination. The performance of three type of magnetic microsphere modified by polyaniline, bovine serum protein and imprinted silica gel were investigated, as well as corresponding synthesis conditions, thermodynamic parameters, dynamic parameters and possible application for spectrophotometric determination of Chromium(?,VI) and Lead(II).Firstly, Fe3O4 was synthesized by co-precipitation method with Fe2+/Fe3+/sodium hydroxide molar ratio of 1:1.75:6, reaction time of 2 hours. After that, SiO2/Fe3O4 was synthesized by sol-gel method uding ethyl silicate as silicon source. XRD and concentrated acid corrosion test confirmed the effective coating of SiO2 on Fe3O4 surface.Secondly, polyaniline, polyaniline/Fe3O4, cross-linked polyaniline/Fe3O4 were synthesized. Together with Fe3O4, theses materials were used for chromium(VI) extraction. The effects of pH, time, temperature on chromium(VI) extraction by each of these material were investigated. Under the optimized conditions, the maium extraction capacity chromium(VI) on Fe3O4, polyaniline, polyaniline/Fe3O4, crosslinked polyaniline/Fe3O4 was 0.21 mg/g, 21.60 mg/g, 29.50 mg/g and 16.50 mg/g respectively. Further experiments investigated the influence of polyaniline /Fe3O4 synthesis conditions on chromium(VI) extraction. The results indicated that a maximum extraction ratio of chromium(VI) on polyaniline/Fe3O4 could be obtained under a synthesis condition of 5 oC, after take this solution into refrigerator ice water bath, 50 mL 0.4 mol/L hydrochloric acid into 1.0 g Fe3O4 and acid aniline solution, and next 50.0 mL 1.0 mol/L ammonium persulfate was added drop by drop, followed by freezing in refrigerator for 12 hours.Next, bovine serum proteins modified Fe3O4 microspheres were synthesized and were used for Pb(II) extraction and spectrophotometric determination. Absorption experiments investigated the influence of extraction conditions on Pb(II) extraction and a maxium extraction capacity is 6 mg/g under selected conditions. Based on the BSA/SiO2/Fe3O4 extraction, a spectrophotometric method for Pb(II) detection was developed. The standard curves has a good linear relationship with Pb(II) concentration with a regression equation of A=0.1888C+0.0061, and a correlation coefficient of R=0.9989. The detecton limit is 6.2 ?g/L. The within-day precision was 17.1% and intra-day precision was 15.8%, the recovery ratio was ranged from 83% to 103% by spiking Pb(II) standard.In the last chapter, Pb(II) imprinted magnetic adsorbent was obtained and was used as adsorbent for Pb(II) extraction and its spectrophotometric determination. The maximum extraction capacity of imprinted and non-imprinted adsorbent was 8.85 mg/g and 2.80 mg/g, respectively.