Modeling of adsorption process establishes mathematical relationship between the interacting process variables and process optimization is important in determining the values of factors for which the response is at maximum. In this paper, response surface methodology was employed for the modeling and optimization of adsorption of phenol onto rice husk activated carbon. Among the action variables considered are activated carbon pretreatment temperature, adsorbent dosage, and initial concentration of phenol, while the response variables are removal efficiency and adsorption capacity. Regression analysis was used to analyze the models developed. The outcome of this research showed that 99.79% and 99.81% of the variations in removal efficiency and adsorption capacity, respectively, are attributed to the three process variables considered, that is, pretreatment temperature, adsorbent dosage, and initial phenol concentration. Therefore, the models can be used to predict the interaction of the process variables. Optimization tests showed that the optimum operating conditions for the adsorption process occurred at initial solute concentration of 40.61 mg/L, pretreatment temperature of 441.46 ∘ C, adsorbent dosage 4 g, adsorption capacity of 0.9595 mg/g, and removal efficiency of 97.16%. These optimum operating conditions were experimentally validated.
<p>In this study, low-cost adsorbent was produced and applied in the treatment of Samaru stream water. Treatment of Samaru stream water was carried out in column mode to determine the efficiency of the low-cost adsorbent for improving the quality of Samaru stream water. To achieve this, the stream water samples were collected from three different points (point 1, 2 and 3) and the values of the following parameters were analyzed before and after treatment: pH, Electrical Conductivity (EC), Total Dissolved Solid (TDS), Biochemical Oxygen Demand (BOD), Chemical Oxygen Demand (COD), Ammonium, Nitrate, Chloride, Iron (III), Copper (II), Lead (II) and Zinc (II). Results obtained from the study show that highest removal efficiency of 96.18 % was attained for chloride and this was followed by 91.76 %, 90.91 % and 90 % for iron (III), copper (II) and ammonium respectively while the least was 6.33 % (pH). Therefore, the high removal efficiency achieved for some sample parameters in the treatment of Samaru stream water implied that the low-cost adsorbent could be employed in the simultaneous removal of contaminants from a multicomponent system.</p>
The conventionally treated drinking water supplied to the Ahmadu Bello University community was assessed for its levels of regulated halo-acetic acids. This is because the Ahmadu Bello University water treatment plant uses calcium hypochlorite in the chlorinated disinfection of its treated water during the treatment process. Longitudinal sampling was undertaken along the treatment and distribution stages of drinking water supply in the community. Between 2008 and 2010, 252 samples were collected and analysed for the regulated halo-acetic acids in accordance with USEPA Method 551.1 (1995) using Methyl Tert-Butyl Ether (MTBE) as extractant and a calibrated Agilent Gas Chromatograph measured their concentrations. All the regulated halo acids recorded their highest concentrations in the chlorinated water sample and these decreased towards house-level water sample except for dichloroacetic acid which increased from the booster station sample with 3.2500E-03±5.8452E-03 mg/L to the house level sample with 3.2511E-03±9.1256E-05 mg/L. The total regulated halo-acetic acid (THAAs) concentrations also decreased from the chlorinated sample concentration of 1.8324E+00±8.1252E-02 mg/L. to the house level concentration of 4.8826E-01±2.8735E-02 mg/L, a situation likely attributable to the turbulent flow during distribution resulting in the increased volatility of the acids in the distribution system. Although not specifically regulated by the Nigerian National Standards, the concentrations of these acids at house level (4.8826E-01±2.8735E-02 mg/L) drinking water is more than the maximum permissible limits of these regulated acids under the USEPA drinking water standard's maximum contaminant level (MCL) of 0.060 mg/L. In view of their implication in increased risk of cancer and other effects including problems of the reproductive system, these acids' concentration in household drinking water need to be rigorously monitored and regulated to minimize their risk to health.
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