| | Biomineralization based remediation of cadmium and nickel contaminated wastewater by ureolytic bacteria isolated from barn horses soil| العنوان باللغة العربية : | | | العنوان باللغة الانكليزية : | Biomineralization based remediation of cadmium and nickel contaminated wastewater by ureolytic bacteria isolated from barn horses soil | | المؤلف : | Hussein J. Khadim | | البريد الالكتروني : | husseinjabar80@yahoo.com | | جهة انتساب المؤلف : | Environmental Engineering Department, University of Baghdad, Baghdad, Iraq | | المشاركين : | Saad H. Ammar , Shahlaa E. Ebrahim | | المستفيدين : | | | المستخلص : | Environmental contamination by toxic heavy metals such as cadmium and nickel is a serious problem. Metal carbonate precipitation has been suggested based on urea decomposition for use in wastewater and soil remediation applications. Therefore, Cd(II) and Ni(II) removal was examined from an environmental viewpoint. In this work, biomineralization of cadmium and nickel in aqueous solutions by sixurease-producing bacterial strains isolated from barn horse’s soil samples has been investigated based on microbially induced precipitation (MIP). The enzyme urease produced by these bacteria can hydrolyze urea to carbonate ions leads to increase pH of the wastewater which results in mineralization of the heavy metal ions and their final conversion to metal carbonates precipitates. Only two bacterial strains have been adopted depending on their ability to tolerate high concentrations of toxic metal ions. Bioprecipitation of Cd(II) and Ni(II) was assessed by consideration some factors that affecting on metal bioprecipitation process. These factors include metal toxicity to the bacteria (in term of initial metal concentration) and treatment time. The bioprecipitates were characterized using scanning electron microscopy (SEM) and X-ray diffraction (XRD). The selected bacterial isolates demonstrated high endurance with toxic heavy metals and therefore, high Cd(II) and Ni(II) removal rates, ranging from 96% for cadmium to 89% for nickel following incubation for 48 h and at 500 mg/L initial concentration of each Cd(II) and Ni(II). Furthermore, coprecipitation of Cd(II) and Ni(II) with calcite precipitation has been also performed and the results demonstrated that this technique can be beneficial for Cd(II) and Ni(II) biosequestration | | المستخلص باللغة العربية : | | | كلمات مفتاحية : | Cadmium,Nickel ,CdCO3,NiCO3,Biomineralization,Bioremediation | | الرابط : | |
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| | | Numerical Modeling of 193-nm Excimer Laser Ablation on CR39 Polymer| العنوان باللغة العربية : | | | العنوان باللغة الانكليزية : | Numerical Modeling of 193-nm Excimer Laser Ablation on CR39 Polymer | | المؤلف : | RANA M. TAHA | | البريد الالكتروني : | engrana.taha32@gmail.com | | جهة انتساب المؤلف : | Institute of Laser for Postgraduate Studies, University of Baghdad, Baghdad, Iraq | | المشاركين : | HUSSEIN A. JAWAD | | المستفيدين : | | | المستخلص : | Laser polymer processing has evolved into an important field of applied and fundamental research. Allyl diglycol carbonate or CR-39 is considered an important polymer for use in optical and medical applications since it is a hard and infusible thermoset plastic that is insoluble in all solvents. The temperature distribution of CR-39 when subjected to irradiation during 193-nm excimer laser ablation was investigated. An effective simulation was developed to reflect the effects of polymer thermal diffusion, laser fluence, beam geometry, and number of pulses. A two-dimensional finite element model was used to predict the temperature distribution and ablation depth in the plastic CR39 polymer under the 193-nm laser ablation process. The photochemical threshold ablation fluence was 750 mJ/cm2 for a single laser pulse, but dropped to 240 mJ/cm2 for repetitive laser pulses. At higher fluence, thermal effects exhibited a slight contribution to the ablation process. For fluence ‡ 750 mJ/cm2 , the ablation depth increased abruptly. It can thus be inferred that the rate of temperature increase with pulse number increased concomitantly with the fluence. Thus, thermal effects are a significant factor in the ablation process. | | المستخلص باللغة العربية : | | | كلمات مفتاحية : | Excimer laser, ablation, CR-39, ablation threshold | | الرابط : | |
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