Fenton’s Oxidation of Selective Herbicides in Water using Lateritic Iron extracted by Acidithiobacillus ferrooxidans BMSNITK17

Abstract

Need for the effective, economical and eco-friendly treatment to degrade the persistent organic pollutants (POP’s) is essential in day to day life. Fenton’s oxidation is one of the proven technologies which have its vast application in the treatment of wide range of organic pollutants. Iron being a catalyst plays a key role demarcating its compulsion in the process. Use of commercial iron in this regard increases treatment cost. Many researchers have been carried out to replace commercial iron with natural laterite iron. Extraction of natural laterite iron by any chemical method again limits its application as its extraction adds up to the cost. Aiming at the replacement of catalytic iron in the Fenton’s oxidation process a detailed study of bioleaching of iron from laterite soil was carried out and the investigation of catalytic role of extracted laterite iron in the Fenton’s oxidation of selective herbicides was done. Novel bacterial strain was isolated and characterized at molecular level by gene sequencing technique and the sequence was submitted to Genbank to get an accession number. Isolated bacteria confirm to be an acidophilic chemolithotrophic bacterium Acidithiobacillus ferrooxidans belongs to the gamma proteo bacterial group with an accession number MG271840. Iron mineral biologically synthesized using isolated strain Acidithiobacillus ferrooxidans BMSNITK17 was characterized and confirms to be biogenic jarosite with XRD and EDS technique. This iron mineral was evaluated for its catalytic role in Fenton’s oxidation for the degradation of ametryn and dicamba. The fresh biogenic jarosite in Fenton’s oxidation was found to degrade ametryn by 84.90 % following alkylic oxidation and hydroxylation pathway which was confirmed with mass spectroscopy studies. Whereas the same mineral shows 91.29 % of dicamba degradation with Fenton’s oxidation process promising cost effective treatment. System conditions like pH, feed mineral particle size, pulp density, temperature, rotor speed has an effect on bioleaching potential of Acidithiobcillus ferrooxidans BMSNITK17 in leaching out iron from laterite soil. Very fast iron dissolution was observed with laterite and soon the drop in the iron concentration of leached solution. The drop in total iron concentration was due to the precipitation of leached iron. Thevi leaching conditions were optimized in the current study with respect to the native bacterial strain Acidithiobacillus ferrooxidans BMSNITK17. Maximum iron concentration leached out accounts to 281.0 mg/L under system conditions like pH 3.0, temperature 30 oC, pulp density 5%, shake flask speed 180 RPM and particle size 150 µm. The bioleached laterite iron (BLFe’s) on evaluation for its catalytic role in Fenton’s oxidation for the degradation of ametryn and dicamba exhibits 94.24 % of ametryn degradation and 92.45% of dicamba degradation efficiency. Fenton’s oxidation performed well with the acidic pH 3. The process follows pseudo first order reaction. Our findings suggest the application of biogenic iron mineral jarosite and bioleached laterite iron as a catalyst in the Fenton’s Oxidation process for treating hazardous herbicides which are the part of an agricultural runoff. The study marks the low cost treatment of hazardous pollutants using naturally available minerals.