R. Boopathy

In situ generation of hydroxyl radical by cobalt oxide supported porous carbon enhance removal of refractory organics in tannery dyeing wastewater.

In this study, cobalt oxide doped nanoporous activated carbon (Co-NPAC) was synthesized and used as a heterogeneous catalyst for the Fenton oxidation of organic dye chemicals used in tannery process. The nanoporous activated carbon (NPAC) was prepared from rice husk by precarbonization followed by chemical activation at elevated temperature (600 °C). The cobalt oxide was impregnated onto NPAC and characterized for UV-visible, Fluorescence spectroscopy, FT-IR, HR-TEM, XRD, BET surface area and XPS analyses. The hydroxyl radical generation potential of Co-NPAC from hydrogen peroxide decomposition was identified (λ(exi), 320 nm; λ(emi), 450 nm) by Excitation Emission Spectra (EES) analysis. The conditions for the degradation of tannery dyeing wastewater such as, Co-NPAC dose, concentration of H2O2, and temperature were optimized in heterogeneous Fenton oxidation process and the maximum percentage of COD removal was found to be 77%. The treatment of dyes in wastewater was confirmed through UV-Visible spectra, EES and FT-IR spectra analyses.

Immobilization of Bacillus sp. in mesoporous activated carbon for degradation of sulphonated phenolic compound in wastewater

Xenobiotic compounds are used in considerable quantities in leather industries besides natural organic and inorganic compounds. These compounds resist biological degradation and thus they remain in the treated wastewater in the unaltered molecular configurations. Immobilization of organisms in carrier matrices protects them from shock load application and from the toxicity of chemicals in bulk liquid phase. Mesoporous activated carbon (MAC) has been considered in the present study as the carrier matrix for the immobilization of Bacillus sp. isolated from Effluent Treatment Plant (ETP) employed for the treatment of wastewater containing sulphonated phenolic (SP) compounds. Temperature, pH, concentration, particle size and mass of MAC were observed to influence the immobilization behavior of Bacillus sp. The percentage immobilization of Bacillus sp. was the maximum at pH 7.0, temperature 20 °C and at particle size 300 μm. Enthalpy, free energy and entropy of immobilization were -46.9 kJ mol(-1), -1.19 kJ mol(-1) and -161.36 JK(-1)mol(-1) respectively at pH 7.0, temperature 20 °C and particle size 300 μm. Higher values of ΔH(0) indicate the firm bonding of the Bacillus sp. in MAC. Degradation of aqueous sulphonated phenolic compound by Bacillus sp. immobilized in MAC followed pseudo first order rate kinetics with rate constant 1.12 × 10(-2) min(-1).

Bioactive prodigiosin-impregnated cellulose matrix for the removal of pathogenic bacteria from aqueous solution

The increase in concern over safe water for human consumption demands disinfection of water. Conventional chemical disinfection methods release counter ions into the treated water and they impair human health significantly. The present investigation was focused on the disinfection of pathogenic bacteria via a bio-disinfection route using a prodigiosin-impregnated cellulose column reactor (PICCR). Escherichia coli and Bacillus cereus were chosen as model pathogens to validate the efficiency of the PICCR for pathogen removal from water. The pathogen removal efficiency was evaluated by the pour plate method, regrowth ability in nutrient broth and quantitative estimation of live and dead cells using fluorescent microscopy. The PICCR showed effective reduction of E. coli by 97.31% and B. cereus by 97.33%. Further, bacterial cell membrane damage by bio-disinfection was verified through analysis of the residual protein and nucleic acid in the treated water using UV-visible spectroscopy, a trans-illuminometer and SDS PAGE. The proposed PICCR was found to be effective for the removal of pathogens from water and this may be regarded as a viable purification technique for drinking water.

Electrochemical treatment of reverse osmosis concentrate generated by the leather industry using a Cu–graphite electrode

Electrochemical treatment of reverse osmosis concentrate (ROC) generated by the leather industry was evaluated using a copper coated graphite (Cu–graphite) electrode for the elimination of refractory organic pollutants. The effect of dilution of the ROC and applied current density on the performance of electrochemical oxidation was investigated. The presence of chloride ions in the ROC favoured the complete elimination of TKN and COD removal by 98% at optimum conditions: current density, 100 mA cm−2 and electrolysis period, 6 h. The increase in ROC dilution slightly decreased the percentage removal of COD from 98% to 96%. The effect of current density on the removal of COD and TKN in raw ROC was found to be lower than in more diluted ROC. It was concluded that electrochemical treatment was more favourable for ROC samples without dilution. The generation of trihalomethanes during the electrochemical oxidation of ROC was effectively removed in an activated carbon packed bed column.

Synthesis of Surface-Modified Iron Oxides for the Solvent-Free Recovery of Bacterial Bioactive Compound Prodigiosin and Its Algicidal Activity.

Prodigiosin (PG) is a bioactive compound produced by several bacterial species. Currently, many technologies are being developed for the production of PG by fermentation processes. However, new challenges are being faced with regard to the production of PG in terms of the recovery and purification steps, owing to the labile nature of PG molecules and the cost of the purification steps. Conventional methods have limitations due to high cost, low reusability, and health hazards. Hence, the present investigation was focused on the development of surface-functionalized magnetic iron oxide ([Fe3O4]F) for solvent-free extraction of bioactive PG from the bacterial fermented medium. Fe3O4 was functionalized with diethanolamine and characterized by FT-IR, diffuse reflectance spectroscopy, thermogravimetric analysis, scanning electron microscopy, and confocal microscopy. The various process parameters, such as contact time, temperature, pH, and mass of Fe3O4, were optimized for the extraction of PG using functionalized Fe3O4. Instrumental analyses confirmed that the PG molecules were cross-linked with functional groups on [Fe3O4]F through van der Waals forces of attraction. PG extracted through Fe3O4 or [Fe3O4]F was separated from the fermentation medium by applying an external electromagnetic field and regenerated for successive reuse cycles. The purity of the extracted PG was characterized by high-performance liquid chromatography, FT-IR, and UV-visible spectroscopy. The iron oxide-diethanolamine-PG cross-linked ([Fe3O4]F-PG) composite matrix effectively deactivates harmful fouling by cyanobacterial growth in water-treatment plants. The present investigation provides the possibility of solvent-free extraction of bacterial bioactive PG from a fermented medium using functionalized magnetic iron oxide.

Simultaneous removal of NH4+-N and refractory organics through sequential heterogeneous Fenton oxidation process and struvite precipitation: kinetic study

The aim of the present investigation was to treat wastewater containing a high concentration of NH4+-N by heterogeneous Fenton oxidation of organics and struvite precipitation. The Fenton reagent (Fe2+/H2O2-10 mM/9.8 mM) and nanoporous activated carbon (30 g L−1) as the heterogeneous matrix were used in heterogeneous Fenton oxidation (HFO) process for the destruction of refractory organic compounds present in ammoniacal nitrogen containing wastewater (ANWW). The HFO process was followed by NH4+-N removal from the ANWW as struvite crystals using MgO and Na2HPO4·2H2O. The maximum removal of NH4+-N as struvite was 96% at solution pH 9.0 and at ambient temperature after the destruction of organic compounds by a HFO process. The optimum time for struvite precipitation was 60 min and secondary crystallization time for struvite crystals was 2 h. The removal of organic impurities was confirmed through FT-IR analysis of struvite crystals formed with and without HFO treatment. The thermal stability of struvite crystals was evaluated by TGA and DTA analyses and enthalpy of formation of struvite was determined through DSC analysis. The orthorhombic crystalline nature of the struvite crystals recovered from ANWW and [ANWW]HFO was evaluated using XRD spectroscopy. The surface morphology of precipitated struvite was analysed using scanning electron microscopy.

Electrochemical treatment of evaporated residue of soak liquor generated from leather industry

The organic and suspended solids present in soak liquor, generated from leather industry, demands treatment. The soak liquor is being segregated and evaporated in solar evaporation pans/multiple effect evaporator due to non availability of viable technology for its treatment. The residue left behind in the pans/evaporator does not carry any reuse value and also faces disposal threat due to the presence of high concentration of sodium chloride, organic and bacterial impurities. In the present investigation, the aqueous evaporated residue of soak liquor (ERSL) was treated by electrochemical oxidation. Graphite/graphite and SS304/graphite systems were used in electrochemical oxidation of organics in ERSL. Among these, graphite/graphite system was found to be effective over SS304/graphite system. Hence, the optimised conditions for the electrochemical oxidation of organics in ERSL using graphite/graphite system was evaluated by response surface methodology (RSM). The mass transport coefficient (km) was calculated based on pseudo-first order rate kinetics for both the electrode systems (graphite/graphite and SS304/graphite). The thermodynamic properties illustrated the electrochemical oxidation was exothermic and non-spontaneous in nature. The calculated specific energy consumption at the optimum current density of 50 mA cm(-2) was 0.41 kWh m(-3) for the removal of COD and 2.57 kWh m(-3) for the removal of TKN.

Electrochemical treatment of evaporated residue of reverse osmosis concentrate generated from the leather industry

Reverse Osmosis (RO) concentrate generated from the leather industry is evaporated through solar pans/multiple effect evaporators as a disposal technique. The evaporated residue (ER) mainly consists of chloride and sulphate ions along with partially oxidized/fresh organic compounds. Earlier studies from us concluded that chloride and sulphate ions could be successfully separated by a selective ion precipitation technique from the saturated solution of ER. In the present investigation, organic compounds present in the ER solution were attempted to be treated by electrochemical oxidation using three different electrode systems: Cu–graphite/Cu–graphite, Ti-MMO/Cu–graphite and SS304/Cu–graphite. Amongst the studied electrode systems Cu–graphite/Cu–graphite and Ti-MMO/Cu–graphite electrode systems were found to be more effective in destruction of organic compounds from ER solution than the SS304/Cu–graphite system at a current density of 50 mA cm−2. The calculated specific energy consumption for the selected electrode system was found to be in the order of Cu–graphite/Cu–graphite > Ti-MMO/Cu–graphite > SS304/Cu–graphite at 50 mA cm−2 for ER treatment. Furthermore the hazardous total trihalomethanes (TTHMs) generated in electrochemical oxidation were removed by adsorption through a mesoporous activated carbon packed bed (MACPB) column. The results revealed that the electrochemically oxidized solution could satisfy the discharge limit after passing through a MACPB column.