Pesticides and organic waste constitute a group of environmental pollutants that are widely distributed in our environment due to various human activities. Adsorptive removal and photocatal...

Recent advances on TiO2-based photocatalysts toward the degradation of pesticides and major organic pollutants from water bodies

Modeling the degradation and disinfection of water pollutants by photocatalysts and composites: A critical review.

In recent years, the application of heterogeneous photocatalytic water purification process has gained wide attention due to its effectiveness in degrading and mineralizing the recalcitrant organic compounds as well as the possibility of utilizing the solar UV and visible light spectrum. This paper aims to review and summarize the recently published works on the titanium dioxide (TiO2) photocatalytic oxidation of pesticides and phenolic compounds, predominant in storm and waste water effluents. The effect of various operating parameters on the photocatalytic degradation of pesticides and phenols are discussed. Results reported here suggested that the photocatalytic degradation of organic compounds depends on the type of photocatalyst and composition, light intensity, initial substrate concentration, amount of catalyst, pH of the reaction medium, ionic components in water, solvent types, oxidizing agents/electron acceptors, catalyst application mode, and calcinations temperature in water environment. A substantial amount of research has focused on the enhancement of TiO2 photocatalysis by modification with metal, non-metal and ion doping. Recent developments in TiO2 photocatalysis for the degradation of various pesticides and phenols are also highlighted in this review. It is evident from the literature survey that photocatalysis has shown good potential for the removal of various organic pollutants. However, still there is a need to find out the practical utility of this technique on commercial scale.

Influence of parameters on the heterogeneous photocatalytic degradation of pesticides and phenolic contaminants in wastewater : a short review

Diclofenac degradation in water by FeCeOx catalyzed H2O2: Influencing factors, mechanism and pathways

Photocatalytic degradation of organic micropollutants: Inhibition mechanisms by different fractions of natural organic matter.

Photocatalytic degradation of carbofuran by TiO2-coated activated carbon: Model for kinetic, electrical energy per order and economic analysis.

The feasibility of batch and continuous (60, 80, and 100 mL/min) mode photocatalysis systems in real-time livestock wastewater treatment was investigated. The photocatalytic experiments were conducted with two types of photocatalysts namely slurry titanium-dioxide (UV-TiO2) and granular activated carbon supported TiO2 (GAC-TiO2). The performance of the systems was compared using economic analysis based on cost and time required to attain maximum efficiency. The photocatalytic reactors operated with GAC-TiO2 was highly effective under both batch (total volatile solids (TVS) removal of 100 % within 6 min and a total operational cost of 0.68 USD per kg of TVS removal) and continuous (at 60 mL/min) (TVS removal of 63 % at a hydraulic retention time (HRT) of 240 min and a total operational cost of 62.16 USD per kg of TVS removal) mode experiments. The economic analyses indicated that cost reduction was a function of optimum time taken for maximum removal efficiency. Subsequently, the experiments were repeated with ultraviolet light (UV) alone, UV-GAC, and GAC alone to quantify effects of adsorption and photolysis. The results confirmed that the effect of GAC in the treatment/degradation of livestock wastewater by adsorption was negligible. However, the presence of GAC in UV systems propelled the rate of biochemical oxygen demand (BOD) and TVS removals. The entire observations reveal that the degradation was mainly by two reaction mechanisms: firstly, adsorption on the GAC surface and secondly by photocatalytic degradation on the GAC-TiO2 surface. Therefore, GAC-TiO2 photocatalysis could be cost-effectively applied for high-rate treatment of industrial wastewaters.

Livestock Wastewater Treatment in Batch and Continuous Photocatalytic Systems: Performance and Economic Analyses

Carbofuran (CBF) removal in a continuous-flow photocatalytic reactor with granular activated carbon supported titanium dioxide (GAC-TiO2) catalyst was investigated. The effects of feed flow rate, TiO2 concentration and addition of supplementary oxidants on CBF removal were investigated. The central composite design (CCD) was used to design the experiments and to estimate the effects of feed flow rate and TiO2 concentration on CBF removal. The outcome of CCD experiments demonstrated that reactor performance was influenced mainly by feed flow rate compared to TiO2 concentration. A second-order polynomial model developed based on CCD experiments fitted the experimental data with good correlation (R2 ∼ 0.964). The addition of 1 mL min−1 hydrogen peroxide has shown complete CBF degradation and 76% chemical oxygen demand removal under the following operating conditions of CBF ∼50 mg L−1, TiO2 ∼5 mg L−1 and feed flow rate ∼82.5 mL min−1. Rate constant of the photodegradation process was also calculated b...

Carbofuran removal in continuous-photocatalytic reactor: Reactor optimization, rate-constant determination and carbofuran degradation pathway analysis.

The present study employed central composite design (CCD) and response surface methodology (RSM) to evaluate the carbofuran removal by photo catalytic process. The carbofuran removal process was carried out in a batch reactor with granular activated carbon (GAC) supported TiO2 (GAC-TiO2) as the photo catalyst. The influence of operating parameters such as initial carbofuran concentration, TiO2 concentration and pH was modelled using CCD and RSM with 11 experimental runs. In the experimental runs, the carbofuran concentration was carried from 1 to 250 mg L, TiO2 concentration was ranged from 5 to 75 mg L and pH was varied from 3-11. The experimental outcomes from CCD revealed an increased carbofuran removal with increase in pH. Complete removal of carbofuran was observed within 240 min in all the runs except in those with higher carbofuran concentration (i.e., 250 mg L) and lower pH (i.e., 3). Furthermore, Polynomial equations were developed to predict the carbofuran removal under different operating conditions. The result indicated that the carbofuran concentraration and pH as well as the interaction term of TiO2 concentration and pH had significant effect on the removal process. Good correlation between observed and predicted values indicated that the developed model can be used to predict the carbofuran removal under different operating conditions within the range that is analysed in this particular study. The optimum conditions for carbofuran removal were observed for a carbofuran concentration of 50 mg L, TiO2 concentration of 5 mg L and pH 7.9. These observations revealed that the carbofuran removal was probably due to the adsorption of carbofuran on the GAC surface and subsequent accelerated degradation of carbofuran on the GAC/GAC-TiO2 surface. Therefore, the adsorbent medium and the adsorbent supported catalyst could be effectively used for efficient treatment of carbofuran contaminated water in a batch-mode photocatalysis system.

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Optimization of GAC supported TiO 2 photocatalytic process for competent carbofuran removal from an aqueous system

In the present study, photocatalytic experiments were performed to investigate carbofuran removal from aqueous solution. The investigation was conducted in a batch-mode photocatalytic reactor. A novel granular activated carbon supported titanium dioxide (GAC-TiO2) was prepared and utilized in this investigation. Batch experiments were conducted for 240 min at a constant carbofuran concentration (250 mg L−1) and at varying GAC-TiO2 concentrations (as TiO2, 5 and 75 mg L−1) and pH (3, 7 and 11). Around 83 % carbofuran removal was observed at pH 7 and 75 mg/L TiO2 concentration after a reaction period of 240 min. Similar carbofuran removal (84 %) was observed under pH 7 and 5 mg/L of TiO2 concentration. On the other hand, the increase in pH from 7 to 11 and the simultaneous decrease in catalyst concentration from 75 to 5 mg/L enhanced the carbofuran removal from 83 to 100 %. The photocatalysis process conducted at acidic pH (i.e. pH 3) and 5 mg/L TiO2 concentration has shown a carbofuran removal of 77 %. The change in TiO2 concentration (i.e. from 5 to 75 mg/L) at pH 3 has not produced any significant increase in the carbofuran removal. The results show that carbofuran removal by photocatalysis was more favored under alkaline pH compared to neutral and acidic pH conditions. The overall observations indicate that the combined form of GAC-TiO2 could be effectively used for efficient treatment of carbofuran contaminated water in a batch-mode photocatalysis system.

M. A. Vishnuganth

Papers

Photocatalytic degradation of carbofuran by TiO2-coated activated carbon: Model for kinetic, electrical energy per order and economic analysis.

Livestock Wastewater Treatment in Batch and Continuous Photocatalytic Systems: Performance and Economic Analyses

Carbofuran removal in continuous-photocatalytic reactor: Reactor optimization, rate-constant determination and carbofuran degradation pathway analysis.

Optimization of GAC supported TiO 2 photocatalytic process for competent carbofuran removal from an aqueous system

Granular Activated Carbon Supported Titanium Dioxide Photocatalytic Process for Carbofuran Removal