ترسيب الزنك النقي من مخلفات البراص بواسطة تآكل إزالة الزنك

Deposition of Pure Zinc from Brass Waste by Dezincification Corrosion

الباحث: مروة فاضل عبد هاشم
المشرف: سامي ابراهيم جعفر الربيعي - فراس فرحان سيد
الجامعة: الجامعة التكنولوجية
الكلية / القسم: قسم هندسة الانتاج والمعادن / هندسة المعادن
الشهادة: ماجستير
السنة: 2022
لغة الرسالة: انكليزي
الكلمات المفتاحية: Dezincification;Brass waste;Zinc recovery;Electrodeposition

Abstract

The effect of increasing the concentration of electrolyte solution and increasing the immersion time on the properties of zinc powder (purity, morphology, and apparent density) resulting from the selective leaching of industrial waste of brass was studied by two processes (electrochemical and immersion process) in this work. In the immersion process, which ranged from one to ten days, the results of Tafel extrapolation of brass were obtained in acidic, neutral and alkaline solutions at pH (1, 7, 10), respectively, in three regions including: the active region (E0), the region of passivation (EP), and the trans-passivation region (Et ). The results of the applied potentials of the acidic solution consisting of 0.1M of hydrochloric acid at PH1 for the three regions (E0, Ep, Et) were (- 66, 1458, 1559) mV , and with a relatively constant current density (I0 Ip, It,) (0.0015) mA /cm2 And for a neutral solution consisting of 3.5% NaCl at PH7 (E0, Ep, Et) (91, 1392, 1493) mV and a current density (I0 Ip, It,) (0.45, 4.16, 6.9) mA / cm2. The alkaline solution consisting of 3.5% NaCl at PH10 (E0, Ep, Et (151, 1627, 1704) mV and the current density range (I0 Ip, It,) (1.34, 5.91, 7.24) mA / cm2. From these extrapolation results, We can determine the minimum voltage that required to initiate the selective leaching of brass and use it in the second process using these induction results, as well as to determine the most suitable solution for conducting the electrochemical process and the permissible potential to break the protective layer and the complete dissolution of zinc. In the electrochemical process and according to Tafel's extrapolation, we used an acidic solution of hydrochloric acid with three different concentrations (0.1, 0.2 and 0.3) M in a galvanic cell consisting of a cathode (stainless steel) and anode (brass), the deposition time was 30 minutes and the distance Between the electrodes 3 cm for all experiments, and the pH of the solution was 1 for the three concentrations, respectively. Applied Voltages according to Tafel extrapolation (1, 1.5, 2, 2.5, 3) volts were used for each concentration and the apparent density of the graphite cathode ranged from 0.47 to 0.89 g/cm3 at 0.3 M, and it was from 0.42 to 0.69 g/cm3 at 0.2 M, and it was from 0.33 to 0.65 g/cm3 at 0.1 M respectively for the applied voltage from 1 volt to 3 volts. That is, increasing the applied voltage reduces the bulk density from 0.89 g/cm3 to 0.33 g/cm3. The increasing the applied voltage reduces the apparent density from 0.89 g/cm3 to 0.33 g/cm3. According to Tafel extrapolation, at low potential both Cu and Zn were dissolved while de-cracking occurred at high potential by selective leaching of zinc. The results showed that the percentage of purity with concentrations (0.1, 0.2, 0.3) M at (1) volt was (94.51, 95.87, 98.03) %, respectively. When the applied voltage reached (1.5) volts, the purity was (90.3, 88.06, 86.89)%, in the same concentrations, and when the voltage reached 2 volts, the purity was (92.04, 87.23, 90.52)%, while at the voltage of 2.5 volts, the purity percentage was (85.63, 82.04, 82.04) %, while the purity at the voltage of 3 volts was (79.28, 78.01, 75.92)% for the graphite cathode. That is, at the high concentration and the lower of the applied potential, the purity rate was increase. The analysis of the microstructure by scanning electron microscope showed that the shape of the resulting zinc particles is a branched dendritic shape and the branching ratio depends on the above-mentioned factors. The results of the analysis of the dynamic light-scattering and zeta potential of the zinc powder produced by electrochemical deposition showed that the structure of the produced zinc is stable -Nano and has good mobility.

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