STUDY OF INFLUENCE OF pH VALUE ON REMOVING OF Cu2+ IONS FROM SOLUTION ONTO PERLITE

Abstract

The expanded perlite was studied as adsorbent for removing of Cu2+ ion from contaminated water. The test conditions were following: pH = 2 – 11; a perlite dosage 0,1 – 1 g; ratio solution: sorbent = 20 – 500 ml : 1 g; basic concentration of the Cu2+ ions 0,5 and 5 mg.1-1, laboratory temperature. The results showed that the perlite shifts the pH value of solutions which have the pH in region of 4 – 9 to neutral region 6 – 7. The pH value of solution was adjusted by HCl/NaOH and McIlvaine (citric acid/Na2HPO4); and Sőrensen (Na2HPO4/KH2PO4) buffer. Top-tests were carried out with solution adjusted by HCl/NaOH. The removing of Cu2+ ions from water relates with the basicity of aqueous solutions. If the ratio of perlite to solution with Cu2+ concentration of 5 mg.l-1 is 1 g : < 40 ml the removal of Cu2+ ions from solution rapidly increases in interval of pH from 4,5 to 5,5 and at pH ³ 6 achieves a maximum. The removal of the Cu2+ ions from initial solution (5 mg.1-1 of Cu2+) is 90 – 95 % at an exposition time of 180 min. and pH > 6. The values from desorption test were about 25 – 30 % lower. The purpose of this paper was to show the influence of phosphate and citrate anions in aqueous solutions on removing of Cu2+ ions from diluted water solution, too. The results confirmed that the citrate anions in the McIlvaine buffer inhibit sorption of Cu2+ on perlite while phosphate anions in Sőrensen buffer generate conditions for formation of Cu2+ precipitates.