CHEMICAL REMEDIATION OF CONTAMINATED SOILS WITH HEAVY MEATALS

This work represents a trial towards ameliorating soil polluted withsome heavy metals (Ni, Co and Cd) resulted from some anthropogenicactivities, i.e., human domestic and industrial wastes. To archive this target,an incubation pot experimental was conducted on two contaminated soilsamples collected from El-Gabal El-Asfar farm (Qalubia Governorate) andEl-Saff (Giza Governorate), which irrigated with sewage effluent andindustrial wastewater, respectively. Before executing this experiment, thestudied two soils were thoroughly mixed with two soil amendments, i.e.,rock phosphate and calcium carbonate at a rate of 2 % for each one, thendaily wetted with distilled water to a constant moisture content (fieldcapacity). Soil samples were taken at incubation periods of 0, 25, 50 and 75days to determine EDTA extractable Ni, Co and Cd for evaluating theeffective role of the tested soil amendments in immobilizing the dominantheavy metal ions. The obtained results could be summarized in thefollowing:1. Increasing time of incubation period between the studied two soils androck phosphate caused progressively decreased in the values of EDTAextractable Ni, Co and Cd. The sorbet amounts of Ni, Co and Cdincreased with prolonging time of contact between rock phosphate andsoil, with the removal percentages followed the descending order: Cd >Ni > Co. The later sequence was changed at the incubation period of 75days in El-Gabal El-Asfar soil, where the sequence of removalpercentages became: Cd > Co ≥ Ni. Also, El-Gabal El-Asfar soil couldbe adsorbed higher amounts of Ni, Co and Cd than El-Saff soil, whilethe reverse was true for the sorption percentages of these metal ions inEl-Saff soil, except for Cd at the incubation period of 75 days.2. Increment of incubation time between soils and CaCO3 led to markedlydecreased in the amounts of EDTA-extractable Ni, Co and Cd, whichseemed a highest capacity with Ni, lowest with Co and intermediatewith Cd. Consequently, it could be categorized these metal ionsaccording to their removal amounts into the following the descendingorder: Ni > Cd > Co regardless of type of soil. The later sequence alsorepresented the removal capacity of CaCO3 for the studied metal ions.