Grantee Research Project Results

This SBIR Phase I project will develop an improved method of feedstock generation for the remediation of organic-toxin contaminated waste waters using nanofiltration. Nanofiltration operating parameters will be optimized to provide appropriately concentrated feedstocks for peroxodisulfate (“persulfate”) generation on diamond anodes, and the diamond electrochemical cell operating parameters will be optimized to provide the highest rate and lowest operating cost for the generation of this versatile and powerful persulfate oxidant.

 

The primary goal of the project was to generate a feedstock from sea water (or concentrated brines) for the production of a strong oxidant capable of remediating organic toxins in wastewater. Given that sulfate is a significant component of sea water and peroxodisulfate (PS), which can be synthesized from sulfate ions, is a strong oxidant, it was proposed that enriching the sulfate concentration through nanofiltration (NF) would be an effective route to producing such feedstocks.

The initial NF attempts at Advanced Diamond Technologies, Inc. (ADT) were unsuccessful. However, one of its customers, Water Tectonics (WTS), who are experts in NF, successfully NFed sea water which was converted to PS at ADT. Concurrently, synthetic feedstocks provided the “proof of concept” for this work. However, they demonstrated that chloride “contamination” was the most critical parameter that inhibiting PS generation.

 

Key specific general operating regimes for the electrochemical synthesis of PS from sulfate/chloride feedstocks were investigated at ADT. PS solutions (mixed with some hypochlorite generated from the residual chloride in the samples) were generated from both the synthetic feedstocks and the NF feedstock from WTS, and they were used to demonstrate the oxidative destruction of phenol, a refractory organic toxin. The yield of non-chlorinated oxidant from the synthesis of PS from the WTS-derived NF sea water sample was considerably higher and therefore demonstrated more effectiveness for the destruction of phenol than synthetic feedstocks of the same sulfate and chloride concentrations. It is hypothesized that this was due to enhancement of carbonate concentration in addition to sulfate during the NF process at WTS that enhanced the yield of oxidant upon synthesis on the diamond anode to include peroxodicarbonate (PC) in addition to PS. This will improve both the efficiency of seawater NF, its conversion to oxidant (both PS and PC), and the cost effectiveness of the whole process for the remediation of organic toxins in wastewater.