Reactive & Functional Polymers, Vol.40, No.3, 263-273, 1999
Electro-partitioning with composite ion-exchange material: an innovative in-situ heavy metal decontamination process
Selective in-situ removal of heavy metals from a contaminated soil/sludge combines the benefits of: (a) being a low risk operation since the soil/sludge is not excavated and transported, (b) being economically prudent since only the target contaminant is removed, and (c) providing the possibility of reuse/recycle of the heavy metals since they are selectively removed. However, the main problem faced in such a process is inserting a material into the soil/sludge which can selectively remove heavy metals from the background of other ions which are much higher in concentration than the target heavy metals but are innocuous from a regulatory point-of-view. The affinity of chelating ion-exchange resins toward heavy metal cations is well established but their morphology (spherical beads of diameter <5 mm) is unsuitable for use in an in-situ process. This communication explores the use of a novel material termed composite ion-exchange material (CIM) which allows microspheres of chelating resins to be entrapped in a Teflon(R) network, thus producing a thin sheet (approximate to 0.5 mm) which can be easily introduced into or withdrawn from a soil/sludge sample. The CIM is used in a physico-chemical process where application of DC potential gradient forces the heavy metal cations to move toward the cathode and consequently contact the CIM sheet wrapped around the cathode. The strong affinity of chelating exchangers inside the CIM forces selective uptake of the heavy metals from the contaminated solid phase. After passage of current for a determined amount of time, the CIM is withdrawn from the soil/sludge and chemically regenerated, thus allowing the heavy metals to be concentrated in an acid solution. This communication presents preliminary results of experiments performed to explore the use of this process and also discusses modifications required to achieve higher suitability.