Jhimli Paul Guin

An insight into the effective advanced oxidation process for treatment of simulated textile dye waste water

The efficiencies of the advanced oxidation processes (AOP) viz. photocatalysis, ozonolysis and gamma radiolysis in the absence and presence of potassium persulfate (K2S2O8) were systematically investigated for the treatment of simulated textile dye waste water (STDWW) containing Reactive Red 120. The oxygen-equivalent chemical-oxidation capacities of photocatalysis, ozonolysis and gamma radiolysis in the absence and presence of K2S2O8 for 16% mineralization of STDWW were calculated as 4.02, 16.19, 0.13, 0.05 kg equiv. O2 m−3, respectively. The gamma radiolysis in the presence of K2S2O8 showed the maximum extent of mineralization among these three AOPs. The pulse radiolysis studies revealed that the favourable reaction of SO4˙− with SDBS (the most robust organic component of STDWW) producing benzyl and hydroxycyclohexadienyl type of radicals caused the enhancement in the extent of mineralization of STDWW during gamma radiolysis in the presence of K2S2O8. The COD of the STDWW was brought down to 1558 ppm from 3128 ppm by gamma radiolysis at 50 kGy dose in the presence of K2S2O8; though that index could not meet the allowed discharge limit (COD ≤ 250 ppm) of industrial effluent in the main water stream. Conversely, on replacing organic acid (CH3COOH) by inorganic acid (H2SO4) in the pH adjustment step, COD of STDWW was brought down to 245 ppm by gamma radiolysis at 60 kGy in the presence of K2S2O8. This paper recommends using H2SO4 in place of CH3COOH in the pH adjustment step followed by the gamma radiolysis of STDWW in the presence of K2S2O8 for an effective effluent treatment.

Evaluation of efficiencies of radiolysis, photocatalysis and ozonolysis of modified simulated textile dye waste-water

The efficiencies of the advanced oxidation processes (AOPs), viz. electron beam radiolysis in the presence of K2S2O8, gamma radiolysis in the presence of K2S2O8, photocatalysis, photocatalysis in the presence of K2S2O8, photolysis in presence of K2S2O8, ozonolysis and ozonolysis in the presence of K2S2O8, were systematically investigated for the treatment of modified (pH adjusted with H2SO4) simulated textile dye waste-water (MSTDWW) containing Reactive Red-120. The efficiencies of these AOPs were investigated in terms of their oxygen-equivalent chemical oxidation capacity, and the cost of energy and other ancillary inputs. The least amount of oxidant was required by electron beam radiolysis compared to the other AOPs studied here, to achieve the same extent of mineralization of MSTDWW. To the best of our knowledge, this study is the first to report an approach to calculate the equivalent cost of gamma radiolysis in comparison to other AOPs consuming electrical energy. Among these AOPs, the electron beam treatment of MSTDWW in the presence of K2S2O8 had the lowest effective cost.

Mineralization and biodegradability enhancement of Methyl Orange dye by an effective advanced oxidation process

An effective process for the oxidation of Methyl Orange dye (MO) was determined by comparing the mineralization efficiency between two advanced oxidation processes (AOPs) viz., ozonolysis and gamma radiolysis in presence and absence of an added inorganic salt potassium persulfate (K2S2O8). The effects of various operating parameters such as ozone flow rate and reaction temperature were optimized to achieve the best possible mineralization extent of MO by ozonolysis. The mineralization efficiency of MO was significantly enhanced during gamma radiolysis in presence of K2S2O8 (γ+K2S2O8) compared to in absence of K2S2O8. The presence of methyl group at the amine of phenyl ring assisted the mineralization of dye during γ+K2S2O8. The oxygen-equivalent chemical-oxidation capacities (OCC) of ozonolysis and γ+K2S2O8 for 75% mineralization of the dye solution were calculated as 7.008 and 0.0336kg equiv. O2 m-3, respectively which signifies that γ+K2S2O8 can be explored as an effective AOP. The non-biodegradable MO dye solution became biodegradable even after the dose of 0.5 kGy during γ+K2S2O8 compared to 1 kGy in absence of K2S2O8. The study concludes that a lower dose γ+K2S2O8 could be one of the efficient pretreatment steps before undergoing biological degradation of dye solution.

Assessment of reaction intermediates of gamma radiation-induced degradation of ofloxacin in aqueous solution

Gamma radiolytic degradation of an antibiotic, ofloxacin (OFX) was investigated under different experimental conditions. The parameters such as initial OFX concentration, solution pH, absorbed dose and the concentrations of inorganic (CO32-) and organic (t-BuOH) additives were optimized to achieve the efficient degradation of OFX. The degradation dose constant values of OFX were calculated as 2.364, 1.159, 0.776 and 0.618 kGy-1 for the initial OFX concentrations of 0.05, 0.1, 0.15 and 0.2 mM with their corresponding (G (-OFX)) values of 0.481, 0.684, 1.755 and 1.971, respectively. Degradation rate of OFX was significantly increased with increase in the absorbed dose and decrease in the initial OFX concentration under acidic condition when compared to neutral or alkaline condition. Reaction of OFX in the presence of CO32- and t-BuOH showed that the degradation was primarily caused by the reaction of OFX with radiolytically generated reactive hydroxyl radicals. Mineralization extent of OFX was determined in terms of percentage reduction in total organic carbon (TOC) and results revealed that the addition of H2O2 enhanced the mineralization of OFX from 29% to 36.1% with H2O2 dose of 0.5 mM at an absorbed dose of 3.0 kGy. Based on the LC-QTOF-MS analysis, gamma radiolytic degradation intermediates/products of OFX were identified and the possible degradation pathways of OFX were proposed. Cytotoxicity study of the irradiated OFX solutions showed that gamma radiation has potential to detoxify OFX.

Performance of hematite particles as an Iron source for the degradation of ornidazole in photo-fenton process

Hematite (α-Fe2O3) particles with varying morphology (rods, spherical, and cubical shapes) were synthesized using sol–gel procedure by modulating the conditions of synthesis like concentration of shape controller additives, time and temperature. Synthesized particles were characterized by X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET), scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS) and transmission electron microscopy (TEM). The activity of hematite particles was evaluated in terms of solar induced photo-Fenton degradation of ornidazole. Complete removal (98%) of ornidazole was achieved with cubical hematite under the optimum operating conditions viz. 10 mM H2O2, 0.13 g/L α-Fe2O3 at pH 3 within 3 h of solar irradiations; however, 51% degradation occurred under similar conditions with UV irradiations. The highest concentration of leached iron in the aqueous solution confirms cubical hematite to be the most photoactive form among the various synthesized hematite particles. HPLC study of solar induced photo-Fenton treatment showed significant reduction in the peak area (R.T. of 5.2 min) with time. Further, TOC study revealed 59% mineralization of 50 mg/L ornidazole solution after 3 h of solar treatment.Graphical abstract

Radiation grafting: A voyage from bio-waste corn husk to an efficient thermostable adsorbent

The initiator free environmentally benign gamma radiation is employed to graft poly-acrylic acid (PAA) onto the widely produced bio-waste corn husk to develop promising, cheap, efficient and reusable adsorbent (AAc-g-husk) having specific adsorption capacity of 1682.7mgg-1 of methylene blue (MB) at pH 9.0 and 320K. The most suitable grafting yield is found by optimizing absorbed dose, dose rate and concentrations of monomer, Mohrs salt and inorganic acid. The inter-planar hydrogen bonding among (002) planes of cellulose in the husk decreases after diversifying grafting of PAA on ad-axial, ribs and micro-fibrils surfaces of the corn husks. The chemically and structurally modified AAc-g-husk shows superior thermal stability. The mechanism of MB dye adsorption by AAc-g-husk has been discussed through six two-parameters adsorption isotherm and ten three-parameters adsorption isotherm models at three different temperatures (300, 310 and 320K), seven kinetic models at room temperature, FT-IR and desorption studies in different solvent compositions.

Efficient degradation of butylparaben by gamma radiolysis.

Gamma radiolysis and ozonolysis are two competitive advanced oxidation processes for degradation of organic pollutants present in the ground water. In this paper, the gamma radiolytic degradation of an emerging organic pollutant Butylparaben (BP) in aqueous solution has been investigated for the first time at different absorbed doses. The effect of the absorbed dose rate in the degradation and mineralization of BP has been investigated. About 65% mineralization of BP was observed at absorbed dose of 70kGy and dose rate of 0.7kGyh-1. Interestingly, turbidity appeared in the solution during radiolysis at doses higher than 2kGy, which disappeared again at very higher dose (~90kGy) making the solution again transparent. At lower dose rate of 0.175kGyh-1 the turbidity was appeared at much lower dose about 1kGy. However, the dose rate showed no effect in the dose of the disappearance of the turbidity. The hydrophobic fragments insoluble in water were generated during the initial stage of gamma radiolysis and those were completely mineralized to CO2 and H2O by direct absorption of gamma radiation. About 90kGy dose was required to achieve ~90% mineralization of BP. On the contrary, maximum 50% mineralization was achieved after 5h of ozonation at the O3 flow rate of 0.5Lmin-1 at pH 7.5 and it remained even constant upon prolonged ozonation. The oxygen-equivalent-chemical-oxidation-capacity (OCC) was used as the parameter to compare the % mineralization efficiencies of the two oxidative processes studied here and the gamma radiolysis was found to be more efficient between those processes. The phytotoxicity of the treated BP solution to agricultural seeds showed that the radiolytically generated fragments were less toxic compared to ozonolytically generated fragments. Thus gamma radiolysis is effective for reducing the organic burden and the toxicity of water polluted with emerging pollutants like BP.