Leema A. Al-Makhadmeh

Generalization of the MAFRAM Methodology for Semi-Volatile Organic Agro-Chemicals

A wide variety of semi-volatile organic chemicals (SVOCs) are still in use in agricultural practices. A proper understanding of the environmental fate and ecotoxicological risk associated with these compounds can aid decision making, particularly regarding product registration and licensing. The aim of this paper is to expand the use of a previously developed Multimedia Agricultural Fate and Risk Assessment Model (MAFRAM) to SVOCs by adopting the fugacity concept as a second criterion to the existing MAFRAM partitioning criterion (i.e., aquivalence). Volatilization processes from surface compartments into the atmosphere were also included. For example, the application of the generalized model was illustrated using an average annual application rate of 4.48xa0kg/ha of chlorpyrifos over a typical homogeneous region. Chlorpyrifos emissions were assumed to take place in three environmental compartments (i.e., soil, air, and aboveground plants) with fractions of 0.1, 0.3, and 0.6, respectively. The trends seen in the modeling results were in good agreement with the existing experimental data. Validation issues in MAFRAM were also discussed. Comprehensive experimental validation is unattainable because of the large scale of the areas covered, the lack of boundaries for the system considered, and the uncertainty in the input parameters.

Removal of iron and copper from aqueous solutions using Jordanian kaolin and zeolitic tuff

AbstractThe goal of this paper is to investigate the removal of iron and copper from aqueous solutions using adsorption. Zeolitic tuff and kaolin were used as adsorbents and were collected from different areas in Jordan. Batch adsorption experiments using synthetic Fe3+ and Cu2+ solutions were employed to study the effects of adsorbent dose, initial concentration, particle size, pH, and temperature on metal uptake. Zeolitic tuff had higher Fe3+ and Cu2+ adsorption capacities (20.70 and 20.83xa0mg/g, respectively) compared with kaolin (14.68 and 9.81xa0mg/g, respectively). The optimum pH values for Fe3+ and Cu2+ removal on kaolin were found to be 4 and 6, respectively. For the initial metal concentration of 100xa0ppm, 100% of Fe3+ and 62% of Cu2+ were adsorbed. As the temperature increased from 25 to 55°C, the adsorption capacity of Fe3+ on kaolin increased, thereby indicating the endothermic nature of the process. At the highest investigated temperature of 55°C, the Fe3+ removal using kaolin was 95.5%. The kine...

The Effectiveness of Zn Leaching from EAFD Using Caustic Soda

Electric arc furnace dust (EAFD) is a toxic waste which is mainly rich in iron oxide, zinc, and lead. Hydrometallurgical extraction of zinc from Jordanian EAFD in alkaline medium was investigated; NaOH, NaHCO3, and Na2CO3 were used as leaching agents. The pH values for the prepared solutions were 8.3, 8.2, and 12.55 for NaHCO3, Na2CO3, and NaOH, respectively. The effect of NaOH concentration (1, 3, 5, 7, and 9xa0M), contact time (5xa0min to 3xa0h), temperature (20, 40, and 60), and solid-to-liquid ratio (SLR; 20, 40, 80, and 120xa0mg/ml) on the leachability of zinc from EAFD were tested. The initial EAFD and the resulting leach residues were characterized using X-ray diffraction (XRD) and X-ray fluorescence (XRF). EAFD contained 25.9% Zn, 18.0% Fe, and 3.2% Pb. A maximum zinc recovery of 92.9% was achieved using 6xa0M NaOH at 60xa0°C with solid loading of 20xa0g/L and 3xa0h leaching time. NaHCO3 and Na2CO3 were not efficient leaching agents for Zn extraction since the recoveries were only 2.6 and 4.5%, respectively. Zn and Pb were depleted in the residues with an E-factor of 0.5–0.6 and 0.1–0.25, respectively. Iron was enriched in the residues; the E-factor was around 2. The EAFD contained mainly zincite, franklinite, and magnetite. After 3xa0h leaching, only traces of zincite exist in the residues, while sylvite and halite were completely dissolved.