Treatment of perchlorate by quaternary amine-modified giant reed and biodegradation by enriched microbial cultures

We investigate the remediation of perchlorate contamination by adsorption onto giant reed modified by quaternary amine (QA) functional groups, followed by reduction of perchlorate by microbial cultures. The effects of pH, contact time, and initial perchlorate concentration on adsorption were investigated using ion chromatography to monitor perchlorate concentration. The adsorption mechanism was explored using Zeta potential analysis and Raman spectroscopy. Studies used a suspension of 2 g/L modified reed (MR) particles ranging in size from 100 to 250 microm. The maximum adsorption capacity for perchlorate, at slightly acidic to neutral pH, was 169 mg/g. The kinetic results agree with a pseudo-second-order model. The isotherm results were best described by the combined Langmuir-Freundlich model. Zeta potential measurements showed that perchlorate adsorption is enhanced by an increase in surface potential upon modification of Giant Reed. Raman spectra results showed that adsorption occurs between the negatively-charged perchlorate anions and the positively-charged amines.;The competitive effect of phosphate and nitrate ions on perchlorate adsorption by MR was investigated in single and binary anion adsorption and equilibrium studies. Both of these competing ions are relatively strongly adsorbed onto MR; adsorption decreases at higher pH. Of the two, phosphate inhibits perchlorate adsorption more strongly than nitrate. Equilibrium results for competitive adsorption of perchlorate with nitrate or phosphate agreed well with a modified Langmuir-Freundlich model.;The perchlorate-laden MR was treated with enriched microbial culture to establish whether biodegradation of perchlorate can be used to decontaminate the spent MR. The anaerobic respiration of these bacteria used Brewer's yeast to reduce the adsorbed perchlorate, producing chloride ions and oxygen gas. Biodegradation was optimized to remove as much as 800 mg/L of perchlorate in 24 hours. A new method was developed to quantify the total amount of perchlorate in biomass using microwave-assisted extraction followed by ion chromatography. The extraction efficiency was optimized to reach 90% recovery. Thus, the remediation of perchlorate from surface and groundwater can be achieved through adsorption onto quaternary amine-modified Giant Reed followed by biodegradation in a clean, cost-effective, and efficient process.