Calibration and Validation of a Two-Step Kinetic Mathematical Model for Predicting Cu Extraction Efficiency in an EDDS-Enhanced Soil Washing

The kinetic trend for Cu extraction from contaminated soil through ethylenediamine-N, N'-disuccinic acid (EDDS)-enhanced soil washing is investigated. Long-term tests are conducted over 96 h at five different values of EDDS-Cu (M) molar ratio (mol/mol) and five different values of liquid-to-soil (L/S) ratio (v/w). The overall Cu extraction efficiency at different M ratios ranges from similar or equal to 47 to similar or equal to 60 % as the ratio increases from stoichiometric values to EDDS excess (M = 50). An increase in the L/S ratio generally leads to the Cu extraction efficiency decrease, from similar or equal to 60 % (L/S = 5) to similar or equal to 49 % (L/S = 45). The highest decrease of Cu extraction yield is observed while increasing the L/S ratio from 5 to 15, with negligible differences occurring as the L/S ratio increases further. The collected data show a two-step kinetic tendency during the extraction process, first characterized by a fast extraction kinetic which is followed by a slow extraction step. Two sets of experimental data are used for calibration and validation of a two-step mathematical model used to simulate Cu mobilization efficiency as a function of treatment time and M ratio. The proposed model is a useful tool for Cu extraction efficiency prediction and can be applied to improve the decision-making process regarding the EDDS-enhanced soil washing approach.