Papers by Author: Usa Onthong

Abstract: The adsorption of hydrogen sulfide (H₂S), carbondioxide (CO₂) and methane (CH₄) on H-FER zeolite was investigated under computational chemistry using ONIOM (HF/6-31G (d,p):UFF) and ONIOM (B3LYP/6-31G (d,p):UFF) method. Compared to the H-FER zeolite induces much stronger binding of H₂S, CO₂ and CH₄ suggesting great enhancements in the adsorption selectivity. The order of binding energies of adsorbed molecules is H₂S > CO₂ > CH₄. It was found that the extended zeolitic framework covering the nanocavity was essential for describing the confinement effect of the zeolite. The results of these calculations show that the zeolite can be used to adsorb H₂S bester then CO₂ and CH₄. Carbondioxide and hydrogen sulfide are pollutant in biogas product from anaerobic digestion of biodegradable materials. There for, zeolite can be use to purified gas before using as fuel.

Abstract: The removal of the cadmium ion from aqueous solution was studied in batch experiments using five natural zeolites were obtained from South of Thailnd, Clinoptiolite, Mordenite, Willhensonite, Offretite and Ferrierite, on the basis of experimental models on laboratory scale. Clinoptiolite was used for preliminary study of the adsorption parameters. An hour contact time and 40 g/L of the ratio of zeolite per water sample are optimum adsorption parameters with an average cadmium removal efficiency of 91.68 %. The optimum adsorption conditions were then used for other four natural zeolites. The results show that the effective removal sequence can be listed as Offretite  Clinoptiolite > Willhensonite > Mordenite > Ferrierite. Clinoptiolite, Offretite and Willhensonite are successfully used to reduce significantly cadmium from sample water with removal efficiency ranging from of 87-92%, respectively. Accordingly, the natural zeolites are recommendable adsorbents for highly cadmium removal of industrial wastewater with low cost of wastewater treatments and environmentally friendly chemical processes.

Abstract: The scopes of this research were to investigate efficiency of anaerobic digestion system to treat wastewater from air dried rubber sheet production process and to produce and use biogas from this system. Wastewater from air dried rubber sheet production process contains high organic substance and pH about 4.6. Therefore, this wastewater must be adjusted pH to be 7 before feeding to system in start-up period. Two tanks system (The system consisted of 2 digestion tanks, each tank was operated at HRT 7.5 days, total HRT was 15 days) provided higher wastewater treatment efficiency than one tank system (The system consisted of 1 digestion tank, it was operated at HRT 15 days). In this research, full-scale reactor (two tank system, total volume was 800 liters) was set up and operated at agriculturist’s home in Nakorn Sri Thamaraj, Thailand. From the first day to the fifteenth day of operating period, wastewater was adjusted pH from 4.6 to be 7.0 before feeding into reactor. After that, reactor was fed with wastewater which was not adjusted pH (pH about 4.6). The results of full-scale shown that this system provided average removal efficiency of COD, BOD, TSS, TKN and TP about 69.23%, 66.86%, 63.16%, 35.81% and 36.74%, respectively. Biogas production rate of full-scale system was 0.45 m3-gas/m3-reactor.day (0.57 m3-gas/kg CODremoved). Total biogas from full-scale reactor (800 liters) was 360 liters per day; it can be used for cooking about 2 hours per day. Compositions of biogas were methane 65%, carbon dioxide 32% and another gas such as nitrogen and hydrogen sulfide 3%.