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Articles by A. Maleki
Total Records ( 3 ) for A. Maleki
  A. H. Mahvi , A. Maleki and A. Eslami
  The potential of rice husk and rice husk ash for phenol adsorption from aqueous solution was studied. Batch kinetics and isotherm studies were carried out under varying experimental conditions of contact time, phenol concentration, adsorbent dose and pH. Adsorption equilibrium of rice husk and rice husk ash was reached within 6 hr for phenolic concentration 150-500 μg/L and 3 hr for phenol concentration 500-1300 μg/L, respectively. Kinetics of adsorption obeyed a first-order rate equation. The adsorption of phenol increases with increasing the solution pH value. The suitability of the Freundlich and Langmuir adsorption models to the equilibrium data were investigated for each phenol-sorbent system. The results showed that the equilibrium data for all the phenol-sorbent systems fitted the Freundlich model best within the concentration range studied. A comparative study showed that rice husk ash is very effective than rice husk for phenol removal. The studies showed that the rice husk ash can be used as an efficient adsorbent material for removal of phenolic from water and wastewater.
  A. H. Mahvi , A. Maleki , R. Rezaee and M. Safari

Humic substances mainly humic acids constitute the major fraction of natural organic matter in water supplies. They play an important role in the formation of harmful disinfection by products. Degradation of humic acids by means of ultraviolet radiation and ultrasonic irradiation processes was investigated in a laboratory-scale batch photoreactor equipped with an 300 W immersed-type medium-pressure mercury vapour lamp and sonoreactor with low frequency (42 kHz) plate type transducer at 170 W of acoustic power with emphasis on the effect of various parameters on degradation efficiency. Experiments were performed at humic acids initial concentrations varying between 2.5-10 mg/L. Oxidation of humic substances has been followed over time by measuring total organic carbon and UV absorbance in 254 nm and 436 nm. Initial results indicated a strong capacity of photolysis for degradation of humic substances. The results also showed that ultrasonic alone cannot be an efficient method for degradation of humic substances in comparison with UV process. The maximum degradation efficiency of humic substances after 90 min of irradiation, however, was only 5.7% and reached a maximum value of 9.5% after 300 min of irradiation. It was found that total organic carbon can be removed effectively by photolysis. It was also found that lower concentrations of humic substances favor the humic substances degradation. Also, the experimental results indicated that the kinetics of ultrasono-oxidation and photo-oxidation processes fit well by pseudo-first order kinetics.

  A. Maleki , A.H. Mahvi , M. Alimohamadi and Azar Ghasri
  The photodegradation of phenol was studied in a batch reactor configuration illuminated with a 400 W medium pressure mercury lamp. The effects of parameters such as pH, kinetic constants and initial phenol concentration on the photolytic degradation and toxicity assay have been studied. The experimental results have shown that lower pH and lower concentration of phenol favor the phenol degradation. The disappearance of phenol in each case approximately obeyed first-order kinetics with the apparent first-order decay constant increasing with decreasing solute concentration. Bioassay tests showed that phenol were toxic to D. magna and so resulted in quite low LC50 values. Comparison of Toxicity Units (TU) between phenol and effluent toxicity has shown that TU value for effluent was 2.18 times lower than that obtain to phenol. Thus, photolysis able to eliminate the toxicity of by-products formed during the degradation of phenol.
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