COPPER(II) RETENTION BY CHERNOZEM, GRAY FOREST, AND DERNOVO-PODZOLIC SOILS: PH EFFECT AND CATION BALANCE

Abstract

Copper(II) retention by Leached Chernozem (LCh), Gray Forest (GFS), and Dernovo-Podzolic (DPS) soils at pH 4, 5, and 6 is accompanied by the simultaneous displacement of both Ca2+ and H+ ions. The amount of Cu(II) sorbed can exceed the effective cation exchange capacity (ECEC) values because copper(II) replaces not only exchangeable metal cations but also H+ ions that are not displaced while estimating ECEC. The amount of (Ca2+ + H+) displaced for LCh and DPS was close to the amount of Cu(II) retained (varied from 0.77 to 1.05 molc molc−1, depending on pH). For GFS the sum of the amounts of displaced ions was less than the amount of Cu(II) retained (from 0.53 to 0.74 molc molc−1). Copper(II) sorption by LCh and DPS can be considered a ternary cation exchange, whereas in GFS we suggest that formation of a positively charged surface complex may be involved. The Cu(II) retention isotherms at all pH values studied for the three soils can be fit equally well to the Freundlich equation, based on the concentration and activity of Cu(II).