Mixed Precipitation Characteristics Of Metals In Highly Alkaline Waste By Cement Kiln’s Exhaust Bubbling

Municipal Solid waste incineration(MSWI) fly ash has much reliance for use, as a resource application, but soluble salts have the pessimistic impacts on the potential use of MSWI fly ash. The water washing process at the different liquid-solid ratios(L/S) 3 m L/g, 8 m L/g & 20 m L/g with the washing time 30 minutes to remove the soluble salts was utilized & observed. Heavy metals leaching, during the washing process, in the wastewater effluent were removed with Ca CO3 and Fe/Al hydroxide precipitations by bubbling CO2 with the effective reduction in the p H to neutral. The effect of various CO2 flow rates, 19.16 m L/min, 13.63 m L/min and 7.81 m L/min, on the removal of heavy metals also investigated. The concentration of metal ions in the wastewater solution after CO2 bubbling was measured by inductively coupled plasma Optical Emission spectrometer(ICP-OES). Moreover, the phase and morphology of the precipitated sediments principally Ca CO3 was inspect by scanning electron microscope(SEM), Fourier Transform Infrared Spectroscopy(FT-IR), X-ray powder diffraction(XRD) and X-ray photoelectron spectroscopy(XPS). The allocation of heavy metals in the precipitated sediment was investigated using SEM equipped with energy dispersion X-ray spectrometry(EDS). The outcome showed that the sediment primarily consisted of Ca CO3 and the other heavy metals are Cd, Cu, Pb, Zn & As. The mechanism of heavy metal precipitation in the solution was studied by using PHREEQC. The precipitate formation of calcite and hydroxides of Cadmium, Iron and Aluminum were examined. The adsorption of Cd, Cu, Pb, Zn, As on Fe and Al colloid and co-precipitation with Ca CO3 was investigated in detail. Hence it is accomplished that accelerated precipitation of calcite and Fe/Al hydroxides were responsible to the removal of trace elements Cd, Cu, Pb, Zn and As from wastewater generated from washing MSWI fly ash through co precipitation. The results show that the amount of Cd, Cu, Pb, Zn and As was significantly decreased after gradually CO2 bubbling to fly ash water. The p H of fly ash water decreased with the CO2 bubbling.