Effect of dissolved oxygen on activated carbon uptake

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" Effect of dissolved oxygen on activated carbon uptake "
N. S. F. Abuzaid

Document Type	:	Latin Dissertation
Language of Document	:	English
Record Number	:	1112836
Doc. No	:	TLpq304113975
Main Entry	:	N. S. F. Abuzaid
Title & Author	:	Effect of dissolved oxygen on activated carbon uptake\ N. S. F. Abuzaid
College	:	King Fahd University of Petroleum and Minerals (Saudi Arabia)
Date	:	1993
student score	:	1993
Degree	:	Ph.D.
Page No	:	397
Abstract	:	Isotherm studies on phenolics show a 20-115% increase in uptake due to the presence of oxygen in the test environment, with the additional uptake increasing with decreasing equilibrium concentrations. The same phenomenon is found when oxidizing agents such as hydrogen peroxide and potassium permanganate are used. Equilibrium data show no such effect on aliphatics. Uptake of domestic and industrial wastewater improve similarly. Telomerization of adsorbates on the carbon surface is suggested as a potential reason for this phenomenon. Two reaction mechanisms are proposed to present the reaction between oxygen and oxidizing agents with phenol on the carbon surface. Experimental data indicate that low pH favors physical adsorption, while high pH promotes telomerization. The optimum pH for adsorption of phenolics under oxic conditions is pH 7. Lower temperatures favored physical adsorption and higher temperature results in significant enhancement in the uptake under oxic conditions. Uptakes or phenol and o-cresol increase with the increase in the DO concentration. THe quantities of dimers and trimers formed on the carbon surface are a function of the DO level. Phenol yield efficiencies around 70% and 25% are observed for anoxic and oxic loadings, respectively. The additional uptake attained under oxic conditions is limited by the mass of DO as well as the mass for GAC in the test environment. Two models relating the oxic uptake to the ratio of DO to GAC mass and the anoxic capacities are developed. The apparent surface diffusivity coefficient for phenol and o-cresol in GAC decreases with increasing DO levels in the sorbate solution. Equilibration time for physical adsorption increases proportionally with pH and inversely with temperature, while, for the oxic case, the equilibration time occurs in the time range of (7.5-11) days from the beginning of the experiment. usdD\sb{s}usd values for the oxic cases increase proportionally with temperature and inversely with pH, with the highest difference between oxic and anoxic diffusivities at pH 7 and 35C. A mathematical model which incorporates the observed reactions with adsorption is formulated. In that model the reaction is assumed to be first order with respect to the capacity and not limited by dissolved oxygen existence. The column experiments have shown that DO cases a delay in the breakthrough curve (BTC), resulting in a completely different BTC. The issue of discrepancies between isotherm capacities and column capacities is resolved. The HSDM is found to have food prediction capability (before tailing).
Subject	:	Applied sciences
	:	Civil engineering
	:	oxygen