Browsing by Author "Remya, Neelancherry"

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Carbofuran degradation by the application of MW-assisted H2O2 process
(2011-01-01)
Remya, Neelancherry
;
Lin, Jih-Gaw
;
環境工程研究所
;
Institute of Environmental Engineering
Carbofuran removal performance of a microwave (MW)-assisted H2O2 system under different MW-power levels (300-900 W) was investigated. Batch experiments were conducted at 100 mg/L carbofuran concentration using a modified-MW reactor with 2450 MHz of fixed frequency. As a precursor, control experiments were carried out with H2O2 alone, MW alone and conventional heating (CH). A maximum carbofuran removal of 14 % was observed in both H2O2 alone and CH systems. On the other hand, only 2 % removal was observed in the MW alone system irrespective of the operation-mode, i.e. continuous or pulsed. The combination of MW and H2O2 produced 100 % carbofuran removal in all the MW-assisted experiments. The MW-assisted system operated under continuous-mode and at 750 W has showed rapid carbofuran degradation, i.e. 30 sec, with the highest first-order removal rate constant of 25.82/min. However, 97 % carbon oxygen demand (COD) removal was observed in the same system only after 30 min. On the other hand, 100 % carbofuran removal and 49 % COD removal were observed in the pulsed-mode MW-assisted H2O2 system after 10 and 30 min, respectively. Carbofuran mineralization in the system was evidenced by the formation of ammonium and nitrate, and carbofuran intermediates.
Carbofuran degradation by the application of MW-assisted H2O2 process
(2011-01-01)
Remya, Neelancherry
;
Lin, Jih-Gaw
;
環境工程研究所
;
Institute of Environmental Engineering
Carbofuran removal performance of a microwave (MW)-assisted H2O2 system under different MW-power levels (300-900 W) was investigated. Batch experiments were conducted at 100 mg/L carbofuran concentration using a modified-MW reactor with 2450 MHz of fixed frequency. As a precursor, control experiments were carried out with H2O2 alone, MW alone and conventional heating (CH). A maximum carbofuran removal of 14 % was observed in both H2O2 alone and CH systems. On the other hand, only 2 % removal was observed in the MW alone system irrespective of the operation-mode, i.e. continuous or pulsed. The combination of MW and H2O2 produced 100 % carbofuran removal in all the MW-assisted experiments. The MW-assisted system operated under continuous-mode and at 750 W has showed rapid carbofuran degradation, i.e. 30 sec, with the highest first-order removal rate constant of 25.82/min. However, 97 % carbon oxygen demand (COD) removal was observed in the same system only after 30 min. On the other hand, 100 % carbofuran removal and 49 % COD removal were observed in the pulsed-mode MW-assisted H2O2 system after 10 and 30 min, respectively. Carbofuran mineralization in the system was evidenced by the formation of ammonium and nitrate, and carbofuran intermediates.
Current status of microwave application in wastewater treatment-A review
(2011-02-01)
Remya, Neelancherry
;
Lin, Jih-Gaw
;
環境工程研究所
;
Institute of Environmental Engineering
Microwave (MW) irradiation has gained a great deal of attention owing to the molecular level heating. However, the commercialization of MW technology for real-time wastewater (WW) treatment requires the understanding of basic mechanism of MW and MW coupled treatment methods. This review addresses the basic theory and mechanism of MW, current application of MW in WW treatment, MW reactors and economical aspects of MW in WW treatment. The different combinations of MW application in WW treatment, including MW alone, MW with oxidants, MW with catalyst and MW with advanced oxidation processes (AOPs) are discussed in detail. Moreover, the effect of MW heating and the factors affecting MW coupled treatment methods are discussed with respect to the treatment efficiency. Finally, the future research challenges in the application of MW for WW treatment are emphasized. (C) 2010 Elsevier B.V. All rights reserved.
Influence of organic matter and solute concentration on nitrate sorption in batch and diffusion-cell experiments
(2011-05-01)
Remya, Neelancherry
;
Kumar, Mathava
;
Mohan, S.
;
Azzam, Rafig
;
環境工程研究所
Nitrate sorption potentials of three surface soils (soils-1-3) were evaluated under different solute concentrations. i.e. 1-100 mg L(-1). Batch and diffusion-cell adsorption experiments were conducted to delineate the diffusion property and maximum specific nitrate adsorption capacity (MSNAC) of the soils. Ho's pseudo-second order model well fitted the batch adsorption kinetics data (R(2) > 0.99). Subsequently, the MSNAC was estimated using Langmuir and Freundlich isotherms; however, the best-fit was obtained with Langmuir isotherm. Interestingly, the batch adsorption experiments over-estimated the MSNAC of the soils compared with the diffusion-cell tests. On the other hand, a proportionate increase in the MSNAC was observed with the increase in soil organic matter content (OM) under the batch and diffusion-cell tests. Therefore, increasing the soil OM by the application of natural compost could stop nitrate leaching from agricultural fields and also increase the fertility of soil. (C) 2010 Elsevier Ltd. All rights reserved.
Microwave-assisted carbofuran degradation in the presence of GAC, ZVI and H(2)O(2): Influence of reaction temperature and pH
(2011-01-14)
Remya, Neelancherry
;
Lin, Jih-Gaw
;
環境工程研究所
;
Institute of Environmental Engineering
Carbofuran degradation in microwave (MW)-assisted granular activated carbon (GAC)/zero-valent iron (ZVI)/hydrogen peroxide (H(2)O(2)) system(s) was investigated under different reaction temperatures, i.e. 30 degrees C, 50 degrees C and 80 degrees C, and at varying pHs, i.e. 2, 4, 6, 8 and 10. Batch experiments were conducted using a modified-MW reactor (750W power and 2450 MHz frequency) at 100 mg L(-1) carbofuran concentration. The lower MW-reaction temperatures, i.e. 30 degrees C and 50 degrees C, have produced poor carbofuran degradation efficiencies whereas complete carbofuran degradation (100%) was observed at 80 degrees C and pH 6 in all the systems, i.e. MW with GAC, ZVI and H(2)O(2). Under the similar conditions, insignificant carbofuran removal/degradation (2-24%) was observed in the presence of GAC/ZVI/H(2)O(2) without MW. On the other hand, the carbofuran degradation rate was accelerated under the alkaline pHs, i.e. pH 8 and 10 (at 80 degrees C), and 100% carbofuran degradation was observed within 10 min in all the MW-assisted systems. However, the complete carbofuran degradation was accomplished rapidly (5 min) in the MW-assisted GAC and ZVI systems under pH 10 and 80 degrees C. Carbofuran removal in the MW-assisted systems was modeled using the first-order reaction kinetics and a maximum removal rate constant of 4.17 min(-1) was obtained in the MW-assisted ZVI system. A maximum of 86% carbofuran mineralization was achieved in the MW-assisted GAC system via hydrolysis and the removal of carbamate group. The comparison of energy consumption in MW-assisted systems with other processes reveals that the MW-assisted process is highly efficient and cost-effective for carbofuran degradation and mineralization. (C) 2010 Elsevier B.V. All rights reserved.
Microwave-assisted carbofuran degradation in the presence of GAC, ZVI and H2O2: Influence of reaction temperature and pH
(2011-01-14)
Remya, Neelancherry
;
Lin, Jih-Gaw
;
環境工程研究所
;
Institute of Environmental Engineering
Carbofuran degradation in microwave (MW)-assisted granular activated carbon (GAC)/zero-valent iron (ZVI)/hydrogen peroxide (H2O2) system(s) was investigated under different reaction temperatures, i.e. 30 degrees C, 50 degrees C and 80 degrees C, and at varying pHs, i.e. 2, 4, 6, 8 and 10. Batch experiments were conducted using a modified-MW reactor (750W power and 2450 MHz frequency) at 100 mg L-1 carbofuran concentration. The lower MW-reaction temperatures, i.e. 30 degrees C and 50 degrees C, have produced poor carbofuran degradation efficiencies whereas complete carbofuran degradation (100%) was observed at 80 degrees C and pH 6 in all the systems, i.e. MW with GAC, ZVI and H2O2. Under the similar conditions, insignificant carbofuran removal/degradation (2-24%) was observed in the presence of GAC/ZVI/H2O2 without MW. On the other hand, the carbofuran degradation rate was accelerated under the alkaline pHs, i.e. pH 8 and 10 (at 80 degrees C), and 100% carbofuran degradation was observed within 10 min in all the MW-assisted systems. However, the complete carbofuran degradation was accomplished rapidly (5 min) in the MW-assisted GAC and ZVI systems under pH 10 and 80 degrees C. Carbofuran removal in the MW-assisted systems was modeled using the first-order reaction kinetics and a maximum removal rate constant of 4.17 min(-1) was obtained in the MW-assisted ZVI system. A maximum of 86% carbofuran mineralization was achieved in the MW-assisted GAC system via hydrolysis and the removal of carbamate group. The comparison of energy consumption in MW-assisted systems with other processes reveals that the MW-assisted process is highly efficient and cost-effective for carbofuran degradation and mineralization. (C) 2010 Elsevier B.V. All rights reserved.
Microwave-granular activated carbon (MW-GAC) system for carbofuran degradation: Analysis of characteristics and recyclability of the spent GAC
(2015-02-06)
Remya, Neelancherry
;
Lin, Jih-Gaw
;
環境工程研究所
;
Institute of Environmental Engineering
Granular activated carbon (GAC) is frequently used to remove pollutants from wastewater. However, the mechanism of pollutant removal by GAC is by adsorption and hence spent GAC should be regenerated and used for several cycles for minimizing the cost of treatment. In the present study, the characteristics of GAC and carbofuran removal mechanism were explored in a microwave-GAC (MW-GAC) system. Carbofuran removal by adsorption was 52% at a GAC loading of 0.8g/L. However, complete carbofuran degradation from aqueous solution as well as from GAC surface was obtained within 30min in a MW-GAC system. In addition, A COD removal efficiency of 72% was observed in the MW-GAC system at pH 8 and 80 degrees C after 30min. The degradation occurred mainly through cleavage of carbamate group and oxidation of furan ring. Carbofuran removal by adsorption was enhanced with MW exposed GAC due to the improvement in the surface property on exposure to MW. On the other hand, recyclability of MW exposed GAC in the MW-GAC system indicated > 99% degradation of carbofuran in all the three cycles tested. As a whole, complete degradation of carbofuran and the effective recycling of the spent GAC could be achieved in the MW-GAC system.
Optimization of carbofuran degradation in microwave-granular activated carbon system using response surface methodology
(2017-10-01)
Remya, Neelancherry
;
Lin, Jih-Gaw
;
環境工程研究所
;
Institute of Environmental Engineering
Present study revealed tremendous improvement in carbofuran degradation in a Microwave - Granular Activated carbon (MW-GAC) system compared to natural hydrolysis process and the degradation half-life was 12 and 0.189 min at a pH of 6 and 10 respectively at a reaction temperature of 80 degrees C. In addition, the effect of several operating parameters such as carbofuran concentration, MW output power and reaction time was modelled using Central composite design (CCD) and response surface methodology (RSM) with 17 experimental runs. Carbofuran degradation/mineralization process was described in terms of carbofuran concentration, MW output power and reaction time. The experimental outcomes from CCD indicated improved degradation and mineralization of carbofuran with the increase in reaction time. On the other hand, lower MW output power resulted in poor degradation and mineralization of carbofuran. RSM showed highest correlation coefficient for carbofuran removal per MW output power, R-w (0.92) and COD removal efficiency, eta(COD) (0.82). Therefore, quadratic models were developed using regression analysis to predict R-w and eta(COD). Good correlation between the observed values and predicted values by the developed models indicated that the developed models can be used to design required R-w and eta(COD) within the experimental conditions.