| The arsenic and chromium leaded to the environmental pollution problem, which become to current noticeable problems. The contamination of arsenic and chromium in the natural water particularly has been attention. So far, the contamination of arsenic and chromium in drinking water was reported by many countries. The arsenic and chromium were migrated, transformed and aggregated due to natural phenomena and human activities, such as wind reaction, industrial pollution, and using arsenic, chromium compounds. So, they were entered into the environment, which threatened human health and environmental safety. Therefore, the detection and removal technologies of arsenic and chromium in water samples become one of the important research topics in the analytical chemistry and environmental science field. In this paper, eggshell membrane was used as absorbent, through solid phase extraction combined with hydride generation atomic fluorescence spectrometry for trace arsenic in environmental water samples, and removal of Cr(VI) from aqueous solutions on eggshell membrane, and the adsorption study of adsorption isotherms of Cr(VI) from aqueous solutions on powdered activated carbon have been investigeated.1. The eggshell membrane with a unique structure of intricate lattice network composed of amines and amides functional groups showed a predominant ability to capture arsenic(V). The experiment studied that eggshell membrane-based solid phase extraction combined with hydride generation atomic fluorescence spectrometry for trace arsenic in environmental water samples. The optimal solid phase extraction conditions were obtained through investigating in detail. As the results of experiment, effects of the desorption reagent was 6 mL of 2 mol/L nitric acid, the pH of sample solution was 11, the sample flow rate was 3 mL/min, the amount of eggshell membrane was 1000 mg, the volume of sample solution was 200 mL. The content of sodium chloride was systematically optimized and the effects of co-existed ions were also investigated in detail. Under the optimal conditions, the breakthrough capacity of the eggshell membrane biosorbent materials for arsenic(V) was found to be 3.9μg/g. Simultaneously, the relevant parameters of analysis method was determined, the calibration curve was in the range of 0.005-2.0μg/L. The favorable limit of detection (LOD) for arsenic(V) was found to be 0.001μg/L with an enrichment factor of 33.3, and the relative standard deviations (R.S.Ds) was 2.1% for 0.6μg/L arsenic (n=11). The reproducibility among columns was satisfactory (R.S.D. among columns is less than 5%). Three replicate determinations at 0.5μg/L As(V) concentration level were carried out to test the reproducibility among three columns. The R.S.Ds were 2.6 and 4.3% for day-to-day and column-to-column, respectively. As can be seen, R.S.D. (precision) of day-to-day and column-to-column is less than 5%, suggesting the reproducibility among columns is satisfactory. The developed method was also applied to arsenic determination in several environmental water samples, such as a certified reference material, Tap water, Jialing river water, Living sewage, Lake water, Wetland water. The result exhibited that the analytical result of the certified reference was satisfactorily in agreement with the certified value, and the recoveries of arsenic(V) in the spiked environmental water samples ranged from 98 to 113%, which demonstrated that the proposed method was satisfactory for arsenic analysis. This research enlarges the application area of eggshell membrane by pioneering a new aspect as solid phase extration adsorbent with important theoretical significance and wide application prospects, which provides an effective method for extracting and detecting means.2. This preliminary experiment studied that eggshell membrane biomaterial was used as adsorption material, while the performance of absorption capability of chromium(VI) on eggshell membrane was examined. The main results were as follows:(1) In the range of pH 2-10, adsorption chromium(VI) on the eggshell membrane was a reductive process, electrostatic interactions between HCrO4- and the amines or amides of eggshell membrane surface, followed by charge transfer and reduction of chromium(VI) to chromium (III), and finally chromium (III) being retained onto the eggshell membrane surface via interactions with functional groups. (2) The removal efficiency of chromium(VI) increased gradually with increasing of the eggshell membrane dosage. Owing to increase the more adsorption sites on the total eggshell membrane surface. (3) The time of adsorption equilibrium was 120min on eggshell membrane, which indicated that the adsorption process was the rapid adsorption. (4) The effects of several anions and humic acid has been studied, resulting in decreased adsorptive capacity, which maybe competition adsorption between anions or humic acid and chromium(VI). (5) The kinetic data for eggshell membrane adsorbed chromium(VI) could be well described by pseudo-second order rate model, both the initial adsorptive rate v0 and pseudo-second order rate constant k2 increased with the increase of temperature and initial chromium concentration. (6) Under three different test temperatures of 25℃, 35℃and 45℃, the data for eggshell membrane adsorbed chromium(Ⅵ) was well represented by the Langmuir adsorption model. The Gibbs free energy of three different test temperatures of 25℃, 35℃and 45℃were -5.47KJ/mol,-4.81KJ/mol and -2.64KJ/mol, respectively, which shown eggshell membrane adsorbed chromium(VI) that was a spontaneous process. The enthalpy value of-49.83KJ/mol indicated that the adsorption process was exothermic process.3.In this study, the adsorption of chromium(VI) on the powdered activated carbon has been investigated, the removal of chromium(VI) was studied through small scale shake-flask experiments. The effects and adsorption mechanism of sodium chloride, humic acid and cetyltrimethyl ammonium bromide(CTAB) on equilibrium adsorption have been investigated. The isotherms for powdered activated carbon were successful correlated by Freundlich equation and Langmuir equation. The main results were as follows:The pH value greatly influenced powdered activated carbon adsorbed chromium(VI). The temperature little effected on powdered activated carbon adsorbed chromium(VI). When cetyltrimethylammonium bromide and humic acids were added into the sampe solution, the adsorption capacity of chromium(VI) on the powdered activated carbon could increase. The different concentrations of sodium chloride were added, which leaded to reduce the adsorption capacity of chromium(VI) on the powdered activated carbon, it may be due to competitive adsorption between CT and chromium(VI).
|
PDF Full Text Request