Browsing by Author "Manu, Basavaraju"

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Evaluation of Graphene Oxide and Reduced Graphene Oxide for the Removal of Selected Halogenated Phenols from Water
(National Institute of Technology Karnataka, Surathkal, 2020) Catherine, S Hepsiba Niruba.; Manu, Basavaraju
Carbon-based materials especially graphene nanocomposites (GNS) have attracted wide attention in recent years. In this study, graphene oxide (GO) and reduced graphene oxide (rGO) were prepared by Improved Hummers method having high suspension stability in water. Both GO and rGO were investigated for the adsorption of halogenated compounds from water, its stability at the GNS-water interface and its effective application in the debromination of brominated flame retardant. Emerging contaminants (ECs) are compounds of emerging concern that are of raising concern in the past 20 years. ECs such as bisphenol A (BPA), 4-nonylphenol (4-NP) and tetrabromobisphenol A (TBBPA) pose threat to both humans and the ecosystem. GNS including GO and rGO are also considered as EC due to its potential hazard. The adsorption of organic contaminants such as the phenolic ECs on GNS affects the stability at the GNS-water interface and the fate of organic contaminants, thus causing further environmental risk. Various spectroscopic tools such as SEM, TEM, XRD, Raman, FTIR, and XPS were used to characterize the nanomaterial synthesized. The obtained results confirmed that the size of GO and rGO were with a surface area of 2.02 and 227.32 m2/g. The XRD analysis shows that the values of diffraction peak 2θ were 10.01 and 26.09 confining to the synthesized GO and rGO. Later both GO and rGO were used to study the adsorption behaviour of some ECs and common phenolic compounds that include 4-chlorophenol, 2,4-dichlorophenol, 2,4,6– trichlorophenol and phenol considering its stability in water interface were studied. The adsorption capacity of GNS with phenol, TBBPA, and BPA was examined for its thermodynamic equilibrium at different temperatures. The adsorption equilibrium was reached less than 10 h and was fitted using both Langmuir and Freundlich isotherms. The kinetics and isotherms models of the sorption of aromatic compounds on GNS were investigated at ambient conditions. It was also demonstrated that GO and rGO that varied in C/O ratio is identified as an efficient approach for debromination of TBBPA. A pathway of TBBPA, tri-BBPA, di-BBPA, mono-BBPA, and BPA was thus proposed for TBBPA degradation. Debromination was observed by using metal-free carbon-based nanomaterial. The structural defects of GBMs, act as active sites responsible for catalytic performance. Furthermore, ESR analysis provided insights into the evolution of reactive oxygen species (ROS) such as superoxide radical (O⁻ ₂•) and singlet oxygen (1O2) during the debrominationprocess. Therefore, these active species were identified to be the primary radicles generated onto the surface of GBMs, which results in the formation of less brominated BPA. Finally, reuse of the adsorbents for all the pollutants were investigated, and we observed that adsorbent reusability was >93% of its activity up to 5 cycles. These novel findings unveil the crucial role of oxygen functional groups on GBMs surface for the catalytic degradation of TBBPA. These findings emphasize that when carbon-based materials are used for sorption studies of halogenated compounds more attention should be considered on estimating the adsorption capacity in addition to the degradation.
Fenton’s Oxidation of Selective Herbicides in Water using Lateritic Iron extracted by Acidithiobacillus ferrooxidans BMSNITK17
(National Institute of Technology Karnataka, Surathkal, 2020) Bhaskar S.; Manu, Basavaraju
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.
Sequential anaerobic-aerobic treatment of herbicides in water
(National Institute of Technology Karnataka, Surathkal, 2020) Mahesh, G. B.; Manu, Basavaraju
Herbicides are toxic compounds which cause deterioration of the surface and ground water resources, cause harm to all living organisms. Various treatment methods like physicochemical and biological processes and in combination of aforementioned treatment techniques have been suggested for removal of pesticides from water. Under anaerobic reducing conditions, herbicides undergo dehalogenation, dechlorination and demethylation reactions and form substituent which can be further mineralized under aerobic conditions. Therefore, this study was conducted to evaluate the sequential anaerobic-aerobic treatment of three herbicides namely (2-ethylamino)- 4-(isopropylamino)-6-(methylthio)-s-trazine) (ametryn), 3,6-dichloro-2- methoxybenzoic acid (dicamba) and 2,4-dichlorophenoxyacetic acid (2,4-d), and their mixtures in different formulations. The performance was evaluated at hydraulic retention time (HRT) of 48 h, neutral pH between 6.5 – 7.5 and at ambient reactor liquid temperature (27 – 32.2oC). A preliminary study was conducted in four set of sequential anaerobic-aerobic system influent herbicides concentrations of 25 mg/L of 2,4-d, ametryn and dicamba separately and keeping one set as control. The preliminary study was conducted to evaluate the treatment potential of the reactors; significant removal efficiency was achieved for both the herbicides. The long term study was conducted using 4 anaerobic and aerobic reactors namely R1 (anaerobic control with no herbicide), R2 (anaerobic reactor fed with ametryn), R3 (anaerobic reactor fed with dicamba), R4 (anaerobic reactor fed with 2,4-d and ametryn mixture), and R5 (anaerobic reactor fed with 2,4-d ametryn and dicamba mixtures). Effects of increased herbicides concentration when they are treated separately (ametryn and dicamba), and in mixtures (2,4-d with ametryn and 2,4-d, ametryn with dicamba) during 400 – 430 days of treatment period. Five aerobic reactors were operated simultaneously to give post treatment to the anaerobic effluent. The reactors performance was evaluated by monitoring herbicide removal efficiency of ametryn, dicamba, chemical oxygen demand (COD) and biogas production. The reactors stability parameters pH, alkalinity, volatile fatty acids (VFA) and oxidation reduction potential (ORP) were monitored on daily basis. All the anaerobic reactors wereii stabilized using 2 g/L of starch with total organic loading rate (OLR) of 0.21 – 0.215 kg-COD/m3/d during 48 days, and aerobic reactors were stabilized in 14 days using anaerobic effluent as feed having OLR of 0.02 to 0.038 kg-COD/m3/d. After achieving the quasi-state condition the influent was fed with known herbicide concentrations to the respective anaerobic reactors. The maximum removal efficiency obtained for different influent herbicide concentrations under anaerobic treatment from R2 reactor was 88 – 100% for ametryn and 85 – 92% for COD, similarly from R3 about 68 – 80% for dicamba and 77 – 85% for COD respectively. Sequential anaerobic-aerobic removal efficiency was found to be greater than the efficiency of anaerobic reactor, complete removal of ametryn with COD >95% in A2, and >88% for dicamba and COD in A3 was achieved. The mixed herbicides removal efficiency was evaluated based on COD removal efficiency only, the overall COD removal efficiency achieved for different influent concentrations of herbicides mixture was >85%, and >88% respectively from A4 and A5 respectively. Addition of anthraquinone-2,6-disulphonate (AQS) as a redox mediator enhanced the herbicides removal efficiency in the anaerobic reactors R2 and R3 by 12 – 20%, and a slight improvement in the COD removal in the R3 and R4 reactors by 5 – 10%. The GCHRMS and LC-MS analysis was conducted to identify the transformation products (TPs) formed during the treatment process. Commonly identified TPs of anaerobic treatment include long chain fatty acids, esters, and alcohols from all the reactors, which were oxidised in the aerobic reactors and TPs of herbicides were different for the specific herbicides, ametryn TPs were biodegradable under anaerobic condition itself (in R2), while some TPs of dicamba were mineralised in aerobic post treatment step. The effluent from R4 – A4 and R5 – A5 contained different TPs which were not mineralised completely, but removed to a maximum level. Therefore, sequential anaerobic-aerobic treatment is found to be effective and efficient for the removal of selected herbicides from wastewater.