ABSTRACT
A laboratory study was conducted to investigate the ability of activated CO(2)-neutralized red mud (ANRM) for the removal of arsenate from the aqueous solutions. The batch adsorption experiments were conducted with respect to adsorbent dose, equilibrium pH, contact time, initial arsenate concentration, kinetics, Langmuir isotherms. The mechanisms involved in adsorption of arsenate ions on ANRM were characterized by using XRD, FT-IR, UV-vis, SEM/EDX, and chemical methods. The percentage removal was found to increase gradually with decrease of pH and maximum removal was achieved at pH approximately 4. Adsorption kinetic studies revealed that the adsorption process followed pseudo-second-order kinetics and equilibrates within 24 h. FT-IR spectra of ANRM before and after adsorption reveals the binding of arsenate to the adsorbent. The adsorption data were fitted to linearly transformed Langmuir isotherm with R(2) (correlation coefficient)>0.99. Arsenate adsorbed ANRM can be regenerated using NaOH solution at pH 12.0.
Subject(s)
Aluminum Oxide/chemistry , Arsenates/isolation & purification , Carbon Dioxide/chemistry , Industrial Waste , Water Pollutants, Chemical/isolation & purification , Adsorption , Algorithms , Hydrogen-Ion Concentration , Kinetics , Microscopy, Electron, Scanning , Nitrogen/analysis , Solutions , Spectroscopy, Fourier Transform Infrared , Thermodynamics , X-Ray DiffractionABSTRACT
A laboratory study was conducted to investigate the ability of neutralization of red mud (RM) using carbon dioxide gas sequestration cycle at ambient conditions. The neutralized red mud (NRM) was characterized by XRD, SEM, EDX, FT-IR and auto titration method. X-ray diffraction pattern of NRM was revealed that the intensity of gibbsite was increased prominently and formed ilmenite due to dissolution of minerals. EDX analysis was showed that the %(w/w) of Na, C, O, Si were higher in the carbonated filtrate as compared to the RM and NRM. The permanently sequestered CO(2)%(w/w) per 10 g of red mud were approximately 26.33, approximately 58.01, approximately 55.37, and approximately 54.42 in NRM and first, second, third cycles of carbonated filtrate, respectively. The pH of red mud was decreased from approximately 11.8 to approximately 8.45 and alkalinity was decreased from approximately 10,789 to approximately 178 mg/L. The acid neutralizing capacity of NRM was approximately 0.23 mol H(+)/kg of red mud. The specific advantages of these cyclic processes are that, large amount of CO(2) can be captured as compared to single step.
