Cu(II), Cd(II) and Pb(II) removal from aqueous solutions by using pyrite and synthetic iron sulphide

ABSTRACTMASTER THESISCu(II), Cd(II) AND Pb(II) REMOVAL FROM AQUEOUS SOLUTIONSBY USING PYRITE AND SYNTHETIC IRON SULPHIDEArzu ÖZVERDİFırat UniversityGraduate School of Natural and Applied SciencesDepartment of Environmental Engineering2005, Page: 78Copper, cadmium and lead which are used very common in the form of their alloys andcompounds are important heavy metals that are cause water pollution. These metal ions havingdivalent oxidation state in waters must be removed from waters due to their toxiccharacteristics.Heavy metal ions are removed from aquatic environments by different methods such aschemical precipitation, ion exchange, reverse osmosis, cementation and solvent extraction.Because of disadvantages of these methods, adsorption techniques have been investigated inrecent years in order to remove heavy metal ions from aqueous solutions.In this study, the removal of lead, cadmium and copper ions from aqueous solutions bysynthetic iron sulphide and pyrite which is present abundant in nature and occurs as a byproduct of copper production process has been investigated. For this purpose, the effects ofinitial pH of solution, adsorbent dosage, contact time, temperature, initial metal concentrationand organic substances content on removal of discussed heavy metal ions from aqueoussolutions have been explored. Obtained results have been applied Langmuir and Freundlichadsorption isotherms and the adsorption capacities of discussed materials have been calculated.This document was created by Print2PDFhttp://www.software602.comAccording to results obtained, it has been determined that pH, temperature, adsorbentdosage and contact time are important parameter affecting the copper, cadmium and leadadsorption onto both adsorbent. Maximum metal removal efficiency has been obtained at pH 2in the presence of synthetic iron sulphide due to H2S formation at this pH.In order to remove copper ions having the concentration of 100 mg/l, the most suitablepH, adsorbent dosage and contact time have been determined as pH 6, adsorbent dosage of 5 g/land contact time of 45 min for synthetic iron sulphide, pH 6, adsorbent dosage of 5 g/l andcontact time of 120 min for pyrite. Under these conditions, 97.8 % and 47.51 % of copper in thesolution have been removed by synthetic iron sulphide and pyrite, respectively.Maximum Cd(II) removal yields in the 100 mg- Cd(II) /l solutions by synthetic ironsulphide and pyrite have been achieved at the conditions of pH 6, contact time of 120 min andadsorbent dosage of 20 g/l for both adsorbents. The removal yields have been determined to be65.8 % for synthetic iron sulphide and 34.2 % for pyrite.The most effective Pb(II) removal yield has been obtained at pH 5 and in the presenceof adsorption dosage of 3 g/l and for a contact time of 60 min. Under these conditions, it hasbeen determined that 99.5 % and 95.8 % of lead has been removed synthetic iron sulphide andpyrite, respectively.It has been determined that the adsorption yield increases with the increasingtemperature, however, it decrease with the increasing initial metal concentration and thepresence of organic substances.Copper, cadmium and lead adsorptions by synthetic iron sulphide and pyrite fit theLangmuir and Freundlich adsorption isotherms. Copper, cadmium and lead adsorptioncapacities of both adsorbent decrease in the order Pb(II) > Cu(II) > Cd(II). While the copper,cadmium and lead adsorption capacity of synthetic iron sulphide at 25ºC are 120.48, 41.49 and3.05 mg/g, those of pyrite are 133.33, 18.48 and 2.08 mg/g, respectively.Although the adsorption capacities of synthetic iron sulphide is higher than pyrite(except for lead), it has been determined that metal concentrations desorbed from solid residueremained in the adsorption process using synthetic iron sulphide are higher than the limitconcentration value of TCLP (Toxicity Characterization Leaching Procedure). In addition,according to the TCLP test applied the solid residues of adsorption processes, Cu(II) and Cd(II)adsorption residues belong to adsorption process using pyrite and Cd(II) and Pb(II) adsorptionresidues belong to adsorption process using synthetic iron sulphide must not be dischargedirectly and they must be stabilized before discharging.Keywords: Heavy metal adsorption, heavy metal removal, adsorption isotherms, desorption,TCLP.This document was created by Print2PDFhttp://www.software602.com