AbstractIn recent years, the serious problem of water heavy metal pollution affects human health and the stability of the ecological environment. Hexavalent chromium in industrial waste water is a common typical heavy metal ion. Therefore, how to effectively treat heavy metal pollution in water has become a hot topic in the field of water pollution control.
In this research bio-sorbent materials for application in hexavalent chromium removal from waste water were produced and evaluated. The teawaste material was collected from local cafeteria. First, the teawaste material was mixed with bleach until the teawaste paste turned white. Then, the bleach teawaste with iron chloride and heating this resultant mixture at 600℃ for 6 hours in a tubular furnace under nitrogen atmosphere. Finally, the modified teawaste was produced, magnetic bleached teawaste bio-sorbent (MBTW). The effects of initial concentration, amount of adsorbent, adsorption time and adsorption temperature on the adsorption of hexavalent chromium by MBTW were investigated, and the adsorption kinetic, isotherm and thermodynamic parameter of hexavalent chromium by MBTW was analyzed. The results showed that, magnetic bleached teawaste biosorbent (MBTW) the maximum adsorption capacity Qmax was 124 mg/g. At 2.5 g/L, pH=2 and 100 ppm, MBTW equilibrium adsorption quantity qe was 40 mg/g and the hexavalent chromium removal was 100%. At 2.5 g/L, pH=2 and 250 ppm, the amount of total chromium removal by MBTW was 17.8%. The adsorption process of hexavalent chromium by MBTW was more consistent with the pseudo-2 nd -order kinetic model and Freundlich isotherm model. In the pseudo-2 nd -order kinetic model, the adsorption rate constant k2 of MBTW was 0.0279 g/mg/min. This was of great significance for emergency treatment of hexavalent chromium ion wastewater. Thermodynamic studied shown that adsorption process of hexavalent chromium by MBTW was a spontaneous endothermic reaction.
In order to study the effects of process conditions during the production of the MBTW, effect of temperature and duration of the treatment were investigated. The MBTW-(2, 4 and 6) was heating at 450℃ for 2, 4 and 6 hours in a tubular furnace under nitrogen atmosphere. The adsorption test was performed using the three different materials, MBTW-2, MBTW-4 and MBTW-6 to evaluate their performance. The magnetic bleached teawaste bio-sorbent were characterization analyzed by Fourier Infrared spectroscopy (FTIR) and X-Ray diffraction (XRD). The results showed that, MBTW can absorb hexavalent chromium better with produced at lower heating temperature and shorter heating time. For MBTW-2, the maximum adsorption capacity Qmax was 142 mg/g. At 2.5 g/L, pH=2 and 250 ppm, MBTW-2 equilibrium adsorption quantity qe was 64 mg/g, the hexavalent chromium removal was 100% and the amount of total chromium removal by MBTW-2 was 70.6%. The adsorption process of hexavalent chromium by MBTW-2 was more consistent with the pseudo2 nd -order kinetic model and Sips isotherm model. Thermodynamic studied shown that adsorption process of hexavalent chromium by MBTW-2 was a spontaneous endothermic reaction.
|Date of Award||Jul 2020|
|Supervisor||Chirangano Mangwandi (Supervisor) & Bo Xiao (Supervisor)|
- hexavalent chromium