| Summary: | 碩士 === 輔英科技大學 === 環境工程與科學系碩士班 === 97 === With the progress of the times, the prosperity of the Hi-Tech industry, a large amount of GaAs application, produce a great quantity of arsenic wastewater. Among the treatment methods of high concentration arsenic wastewater, general treatment technology needs a high cost, consider to the treatment capability/cost of the factory, so the treatment technology needs improvement. Due to the high removing efficiency of heavy metals for iron oxides, the coating technique was applied to coat iron oxides onto the sand surface, and the iron oxide-coated sand (IOCS) adsorbent was employed to adsorb the high concentration As(V) wastewater through the batch and column experiments. According the experimental results, the operation parameters would be supplied to the practical application in containing arsenic wastewater treatment.
The amount of iron coating onto IOCS surface, the mean deviation ranged from 1.66 to 4.08 %. Following the IOCS dissolving experimental results, the Fe dissolving percentage ranged from 0.04 to 0.15% under various pH values expect 0.01N HNO3 acidic dissolving percentage was equal to 3.2%. According to the batch experimental results, solution pH had a significant influence on the adsorption capability, the adsorption efficiency decreased with pH increased. Adsorption efficiencies of arsenic on IOCS decreased from 50% and 32% to 8% at solution pH increased from 3 to 12 under arsenic concentration 50 mg/L and 100 mg/L, respectively. Beside, solution temperature had a slight influence on arsenic adsorption efficiency. It inferred that the repulsive force increased with solution pH increased. Therefore, the adsorption capacity was reduced through repulsive force increased between arsenic ions and IOCS surfaces.
Following the column experimental results, flow rate, influent arsenic concentration and solution pH had a significant influence on the breakthrough time for removing arsenic ions from water in the continuous column packing with IOCS. The longest breakthrough time was 1,620 minutes under the influent pH 4 and arsenic concentration 10 mg/L. According to the breakthrough data, the phenomenon of multi-layers adsorption could be found in the continuous column experiments. It inferred that the physical and chemical adsorption characteristics existed simultaneously on the surfaces between arsenic ions and IOCS.
According to the pore size distribution analysis results, the majority of pore diameter for pure quartz sand, IOCS and IOCS adsorbed arsenic ions were 345�痋B33�� and 26��, respectively. Obviously, the quartz sand surface was coated by iron oxides, and the pore size distribution of IOCS was similar to that of iron oxide via coating procedure. So, the pore size distribution of IOCS became small through coating iron oxides. Besides, the main pore diameter of IOCS decreased after adsorbing arsenic ions. The results indicated that the arsenic ions were adsorbed by IOCS surface through diffusion into the pores.
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