Author name:
سهى اكرم محمد
Supervisor name:
قاسم جبار سليمان | سيسيليا خوشابا
Abstract:
Electrochemical process is supplying unquestionable amelioration to treat the wastewater pollution, which is a major issue and particularly if the pollutants concerned of multi heavy metal ions. Therefore, two different configurations of electrochemical cells rotating cylinder electrode, RCE and fixed bed flow - by porous electrode, FBPE, in which electrolyte flow is perpendicular to the current flow. They are used to study their effect on the removal of four heavy metal ions being examined, which are : copper Cu(II), cobalt Co(II), cadmium Cd(II), and lead Pb(II)). As single, double, triple, and quaternary ions that were mixed, at different applied currents (150, 180, 250, and 300 mA) by using RCE and (50, 90, 150, 180, and 250 mA) by using FBPE. In addition, different dynamic conditions are examined, which are represented as different rotation speeds in RCE (100, 150, 200, 250, and 300 rpm) and different flow rates in FBPE (100,200,300,400, and 500 l/h). At different deposition times with constant initial concentration of the four metals ions as 125 ppm, the samples have been taken. The supporting electrolyte that is used in all experiments is 0.5 M NaCl at pH 3.5. Where a porous highly conductive material for both electrodes design stainless steel 316 of 60 mesh no.(60 60 pore in inch2) is chosen, to ensure the removal of heavy metals be effective and also the recovery of the deposited metal can be removed without damage the electrodes.The effect of the variation in the initial concentrations on the deposition process has been investigated. The range of initial concentration is from 50 to 200 ppm for Cu(II), Co(II), and Pb(II) ions with different applied currents (120, 180, 250, and 300 mA) and rotation speeds (100, 150, and 200 rpm) at constant time of deposition. Box - Wilson, central composite design, is chosen to carry out investigation and thirty - six response equations are found.The metals deposited on the electrode were recovered, which can be tested by X ray diffraction to characterize the composition of the recovered powder.The scope of the research mainly revealed the followings : The experimental results of the removal rate of the four metal ions : individually and as co - deposition as : binary, ternary, and quaternary metal ions, and at different conditions are presented. Mass transfer coefficients are found, and correlated with applied current and electrolyte velocity, which being more by applied current to increase. The performances of the two configurations are deduced based on the figures of merit for an initial concentration of 125 ppm.as shown in the followed table, Table Abstract - 1 The Maximum values of figures of merit for the two configurations reactor Reactor Design RCE FBPE Heavy metal ions A Applied current 300mA Cu(II) Co(II) Cd(II) Pb(II) At applied current 250 mA Cu(II Co(II) Cd(II) Pb(II) Fraction conversion, % 99.94 80 77.7 99.5 100 98.9 95 100 Mean value of the Space time yield (Kg m - 3 s - 1) 58.6 36.7 35.6 47.6 34.5 25.2 20.3 32.5 Specific energy consumptions Es (KWh/Kg) 1.75 2.03 3.9 5.75 7.2 6.7 13.4 23.5 Normalized space velocity sn (s - 1) *10 - 5 44.8 18.1 17.3 27.9 6.19 1.6 1.1 3.3 Current efficiency % At 150 mA 55.6 38.7 19.4 15.1 At 50 mA30.7 19.32 8.45 8.7 Fraction conversion, % At rotation speed 300rpm 99.5 76 75.4 97.5 At flow rate 300l/h100 97.6 90.4 100 Mean value of the Space time yield (Kg m - 3 s - 1) 27.1 15.7 15 19.4 34.3 25 23.6 33.8 Normalized space velocitysn (s - 1) *10 - 5 36.7 At 300 rpm 38.7 At 100 rpm 19.4 At 100 rpm 15.1 At 100 rpm 5.3 At 400 l/h 1.5 At 300 l/h 1.4 At 300 l/h 4.4 At 300 l/h It is found that copper and lead ions have a catalyzed effect on the deposition of cobalt and cadmium, as they reduced the hydrogen evolution reaction especially at higher applied current and electrolyte velocity. Furthermore, the characteristics of the deposited metal that recovered from the RCE, were examined by X ray diffraction which show high purity metal and binary metal alloys with little amount of impurities as lead oxides where the presence of lead oxides had the effect on producing binary alloys. Copper metal exhibited strongly then secondly lead, which appeared in three different phases and the weekly existence, was for cobalt. Experimental results, analysis and correlations showed good performance of the cell on removal multi metal ions from simulated effluents. Although the FBPE configuration had the magnificent performance by comparing with RCE, RCE had acceptable performance also with comparison with previous workers.
