Retention and Release of Lead by a Silty Loam and a Fine Sandy Loam. II. Kinetics

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Abstract
The kinetics of lead retention and release by a silty loam and a fine sandy loam was investigated. Batch experiments were conducted to assess the rate and degree of lead retention. The rate of lead sorption onto the soils was determined using lead solution with concentrations of 10, 100, and 1000 mg/L. Kinetics of lead retention was very rapid for both soils. Lead was completely removed from both the 10 and 100 mg/L solutions, but partially removed from the 1000 mg/L solutions within the first hour. It was noted that the rate of lead soption was faster for the 10 and 100 mg/L than the 1000 mg/L solutions. The slower retention kinetics for both soils at the 1000 mg/L lead contamination level can be attributed to surface precipitation effects. Batch extraction experiments were also performed using three different types of washing solutions. Lead release using the CaCl2 washes was less than the release using EDTA and HCl, but the kinetics of lead release was initially rapid with most of the removal occurring within the first hour for the three washing solutions. It was observed that the lead solution concentration has no effect on lead removal during the rapid step for the HCl and EDTA washes, but has some effect for CaCl2 washes.