Thiol-SAMMS for liquid applications (THSL) provides an excellent solution for removal of many precious metals (palladium, gold, silver and platinum) from aqueous waste streams. Thiol-SAMMS can treat such metal-contaminated aqueous streams with good kinetics and capacity.
Kinetics
The kinetics of palladium adsorption by Thiol-SAMMS is fast and slightly slower than mercury adsorption. Most adsorption is complete within 20 minute achieving up to a 99.9% reduction of a 1mM Pd2+ buffered solution at pH 4 (Figure 1). The kinetics of platinum is also shown for the same solution. The kinetics of platinum is a little slower but at 500 minutes 99.7% of the platinum was adsorbed.
Figure 1: Palladium and Platinum Adsorption Kinetics
pH Accommodation
Thiol-SAMMS for precious metal adsorption is expected to be applicable across a wide range of pH as seen in mercury adsorption.
The distribution co-efficient, Kd, and Capacity
The Kd (ml/g) for palladium using the solution of Figure 1 is 106 ml/g. The corresponding Kd for platinum is 4 x 104 ml/g. and 60,000 for silver. These numbers show that thiol-SAMMS is highly specific to these metals.
The capacity was measured at 0.098 nM/g for palladium and 0.092 mM/g for platinum.
Cation and Anion Interference
Good capacity and fast kinetics of the SAMMS adsorption should be observed in the presence of most cations and anions. Silver shows insensitivity to PO43-, SO42- , CN-, Ca2+, Cu2+, K+, Na+, Si4+, Zn2+ ; and also in the presence of other anions bound by thiol SAMMS (Ag+, Cd2+, Pd2+, Hg2+, Ni2+). Similar behavior should be expected for platinum and palladium.
Material Properties:
- Bulk Density – The bulk density for THSL is approximately 0.3 g/cc.