Competition Kinetics: An Experimental Approach

In this chapter, free radical kinetics with the help of competition kinetics and some experimental results calculated by competition kinetics to find out the rate constant of reactive species (●OH, eaq−, ●H) with target compound, which is used by radiation chemists is briefly discussed. The competition kinetics method is well validated by taking ciprofloxacin, norfloxacin and bezafibrate as example compounds. The bimolecular rate constants of hydroxyl radical, hydrate electron and hydrogen atom has been calculated for example solute species (ciprofloxacin, norfloxacin and bezafibrate)

Solar light responsive bismuth doped titania with Ti\u3csup\u3e3+\u3c/sup\u3e for efficient photocatalytic degradation of flumequine: Synergistic role of peroxymonosulfate

© 2019 Elsevier B.V. The present study is focused on the synthesis of a novel solar light responsive bismuth doped titania (Bi-TiO2) through a facile so-gel technique by applying various wt% of Bi. The as-synthesized Bi-TiO2 showed superior photocatalytic performance than un-doped TiO2 towards degradation of flumequine (FLU) under solar light irradiation. The as-synthesized material was thoroughly characterized to examine its structure, morphology and chemical states. The EPR analysis revealed the existence of Ti3+ ion and oxygen vacancy, which is created due to Bi-doping. The as-synthesized Bi-TiO2 with 5 wt% Bi (TBi5) showed excellent photocatalytic performance as compared to their counterparts. The photocatalytic activity of TBi5 was further improved when added with peroxymonosulfate (HSO5−) and increased with increasing [HSO5−]0. The mechanistic investigation and radical scavenging studies revealed that [rad]OH and SO4[rad]− are involved in the degradation of FLU by the as-synthesized material. The bimolecular rate constants of [rad]OH and SO4[rad]− were calculated to be 9.1 × 109 M−1s−1 and 8.5 × 109 M−1s−1, respectively. The photocatalytic performance of the as-synthesized TBi5 coupled with HSO5− under solar light irradiation towards degradation of FLU in Milli-Q water (MW), tape water (TW) and synthetic wastewater (SWW) was 92, 82 and 70% with kapp values of 0.093, 0.085 and 0.066 min−1, respectively. Furthermore, the degradation pathways of FLU were predicted on the basis of its degradation products (DPs). The high mineralization of FLU as well as the evaluation of non-toxic DPs suggests that solar light/TBi5/HSO5− is a promising advanced oxidation process for the future wastewater treatment applications

Visible light driven doped CeO2 for the treatment of pharmaceuticals in wastewater: A review

The high-level contamination of pharmaceuticals in aquatic environment, and their toxicities is a serious issue. This review highlights the use of ceria photocatalyst for treatment of pharmaceuticals. Cerium oxide (CeO2) with high oxygen storage, ecofriendly properties, reusability, and photostability contrary to other metal oxides photocatalysts is reportedly a better choice. However, ceria with high band gap energy show photoactivity mainly under UV light. This review highlights pharmaceuticals contamination in water, their contamination level, and toxicities and properties of CeO2 and different approaches used for extending photoactivity of CeO2 under visible irradiation. Metals and non-metals doping is found to promote greatly photoactivity of CeO2 under visible irradiation by narrowing band gap, shift in absorption edge to visible region, crystal defects and yield of oxygen vacancy, lower recombination of conduction band electrons and valence band holes and increasing surface area. The visible irradiation of CeO2 is found to produce hydroxyl radical (OH) and superoxide radical (O2 –) which contribute in pharmaceuticals degradation. The electron paramagnetic resonance spectroscopy and radical scavenger studies confirmed the formation of reactive oxygen species from CeO2 photoactivation. Doping was found to incorporate into the lattice of CeO2 and improve reusability and stability of CeO2 photocatalyst. The suggested mechanisms involved in the treatment of pharmaceuticals through OH and O2 – is discussed. Furthermore, the outlook and future challenges in the use CeO2 for photocatalytic degradation of pharmaceuticals and other organic pollutants are evaluated

Catalytic degradation of carbamazepine by surface modified zerovalent copper via activation of peroxymonosulfate: Mechanism, degradation pathways and ecotoxicity.

ABSTRACTIn this research work, surface modified nano zerovalent copper (nZVC) was prepared using simple borohydride reduction method. The spectroscopic and crystallographic results revealed the successful synthesis of surface modified nano zerovalent copper (nZVC) using solvents i.e., ethanol (ETOH), ethylene glycol (EG) and tween80 (T80). The as-synthesized material was fully characterized for morphological surface and crystal structural properties. The results indicated that EG provides excellent synthesis environment to nZVC compared to ETOH and T80 in terms of good dispersion, high surface area and excellent catalytic properties. The catalytic efficiency of nZVC/EG was investigated alone as well as with the addition of peroxymonosulfate (PMS) in the absence of light. The degradation results demonstrated that the involvement of PMS synergistically boosted the catalytic efficiency of synthesized nZVC/EG material. Furthermore, the degradation products (DPs) of CBZ were determined by GC-MS and subsequently the degradation pathways were proposed. The ecotoxicity analysis of the DPs was also explored. The proposed (nZVC/EG/PMS) system is economical and efficient and thus could be applied for the degradation of CBZ from aquatic system after altering the degradation pathways in such a way that results in harmless products formation

Synergistic effects of H\u3csub\u3e2\u3c/sub\u3eO\u3csub\u3e2\u3c/sub\u3e and S\u3csub\u3e2\u3c/sub\u3eO\u3csub\u3e8\u3c/sub\u3e\u3csup\u3e2−\u3c/sup\u3e in the gamma radiation induced degradation of congo-red dye: Kinetics and toxicities evaluation

© 2019 Elsevier B.V. Gamma radiation has received increasing attention due to their high potential in degradation of recalcitrant pollutants. Thus in the present study, gamma radiation was used for degradation of congo-red (CR) dye, a highly toxic and carcinogenic pollutant, in the presence of H2O2 and S2O82−. The CR was significantly degraded by gamma radiation (i.e., 53%), however, presence of H2O2 and S2O82− promoted degradation of CR to 98 and 87%, respectively, at 1184 Gy absorbed dose. The radical scavengers and electron spin resonance studies revealed that gamma radiation decompose H2O2 and S2O82− into [rad]OH and SO4[rad]− and both [rad]OH and SO4[rad]− caused degradation of CR. The CR showed high reactivity, i.e., 3.25 × 109 and 8.50 × 108 M−1 s−1 with [rad]OH and SO4[rad]−, respectively, and removal of CR was inhibited in the presence of [rad]OH and SO4[rad]− scavengers. The removal of CR was promoted with elevating initial concentrations of H2O2 and S2O82− and decreasing initial concentrations of CR. pH of aqueous solution also significantly influenced removal of the dye. The proposed degradation pathways of CR were established from the [rad]OH mediated degradation of CR and nature of identified degradation products. The greater mineralization of CR, formation of small molecular mass degradation product, and decline in concentration of acetate after extended treatment suggest the gamma-ray mediated peroxide based process to be a promising alternative for potential degradation of CR

Preparation of H3PO4 modified Sidr biochar for the enhanced removal of ciprofloxacin from water

In this study, biochar was prepared from Sidr plant leaves and used for the treatment of ciprofloxacin (CIP)-contaminated water. CIP is important class of emerging water pollutants from pharmaceutical industries. The biochar showed 65% adsorption efficiency and 43.48 mg/g adsorption capacity of CIP. Adsorption efficiency as well as adsorption capacity were improved to 91% and 62.50 mg/g, respectively, by phosphoric acid (H3PO4) modified biochar. Removal of CIP by the prepared biochar was due to different surface functional groups of CIP and biochar as revealed from the study of different characterization analyses. The presence of PO43- group in modified biochar led to maximum binding of CIP. Also, the modified biochar showed higher reusability potential and less leaching of ions when compared to the raw biochar. Removal of CIP was affected by concentrations of CIP, the amount of biochar and different pH\u27s; the maximum removal of CIP was achieved at pH 4. The Freundlich and pseudo-first-order models best fitted the removal of CIP by modified biochar. Advanced characterization techniques were applied to investigate surface and physiological characteristics of the biochar and modified biochar. The modification showed high impact on the performance and stability of biochar. The study showed significant impacts of modification on the potential of the biochar for treatment of CIP-contaminated water

Development of zerovalent iron and titania (Fe0/TiO2) composite for oxidative degradation of dichlorophene in aqueous solution: synergistic role of peroxymonosulfate (HSO5−)

Abstract Binary composite of zerovalent iron and titanium dioxide (Fe0/TiO2) was synthesized for the catalytic removal of dichlorophene (DCP) in the presence of peroxymonosulfate (PMS). The as-prepared composite (Fe0/TiO2) exhibits synergistic effect and enhanced properties like improved catalytic activity of catalyst and greater magnetic property for facile recycling of catalyst. The results showed that without addition of PMS at reaction time of 50 min, the percent degradation of DCP by TiO2, Fe0, and Fe0/TiO2 was just 5%, 11%, and 12%, respectively. However, with the addition of 0.8 mM PMS, at 10 min of reaction time, the catalytic degradation performance of Fe0, TiO2, and Fe0/TiO2 was significantly improved to 82%, 18%, and 88%, respectively. The as-prepared catalyst was fully characterized to evaluate its structure, chemical states, and morphology. Scanning electron microscopy results showed that in composite TiO2 causes dispersion of agglomerated iron particles which enhances porosity and surface area of the composites and X-ray diffraction (XRD), energy dispersive X-ray (EDX), and Fourier-transform infrared (FTIR) results revealed successful incorporation of Fe0, and oxides of Fe and TiO2 in the composite. The adsorption–desorption analysis verifies that the surface area of Fe0/TiO2 is significantly larger than bare Fe0 and TiO2. Moreover, the surface area, particle size, and crystal size of Fe0/TiO2 was surface area = 85 m2 g−1, particle size = 0.35 μm, and crystal size = 0.16 nm as compared to TiO2 alone (surface area = 22 m2 g−1, particle size = 4.25 μm, and crystal size = 25.4 nm) and Fe0 alone (surface area = 65 m2 g−1, particle size = 0.9 μm, and crystal size = 7.87 nm). The as-synthesized material showed excellent degradation performance in synthesized wastewater as well. The degradation products and their toxicities were evaluated and the resulted degradation mechanism was proposed accordingly. The toxicity values decreased in order of DP1 \u3e DP5 \u3e DP2 \u3e DP3 \u3e DP4 and the LC50 values toward fish for 96-h duration decreased from 0.531 to 67.2. This suggests that the proposed technology is an excellent option for the treatment of antibiotic containing wastewater.Graphical abstrac

Topical curcumin nanocarriers are neuroprotective in eye disease

Curcumin (1,7-bis-(4-hydroxy-3-methoxyphenyl)-1,6-heptadiene-3,5dione) is a polyphenol extracted from turmeric that has long been advocated for the treatment of a variety of conditions including neurodegenerative and inflammatory disorders. Despite this promise, the clinical use of curcumin has been limited by the poor solubility and low bioavailability of this molecule. In this article, we describe a novel nanocarrier formulation comprising Pluronic-F127 stabilised D-α-Tocopherol polyethene glycol 1000 succinate nanoparticles, which were used to successfully solubilize high concentrations (4.3 mg/mL) of curcumin. Characterisation with x-ray diffraction and in vitro release assays localise curcumin to the nanocarrier interior, with each particle measuring <20 nm diameter. Curcumin-loaded nanocarriers (CN) were found to significantly protect against cobalt chloride induced hypoxia and glutamate induced toxicity in vitro, with CN treatment significantly increasing R28 cell viability. Using established glaucoma-related in vivo models of ocular hypertension (OHT) and partial optic nerve transection (pONT), topical application of CN twice-daily for three weeks significantly reduced retinal ganglion cell loss compared to controls. Collectively, these results suggest that our novel topical CN formulation has potential as an effective neuroprotective therapy in glaucoma and other eye diseases with neuronal pathology

Bismuth-Doped Nano Zerovalent Iron: A Novel Catalyst for Chloramphenicol Degradation and Hydrogen Production

© In this study, we showed that doping bismuth (Bi) at the surface of Fe0 (Bi/Fe0, bimetallic iron system) - synthesized by a simple borohydride reduction method - can considerably accelerate the reductive degradation of chloramphenicol (CHP). At a reaction time of 12 min, 62, 68, 74, 95, and 82% degradation of CHP was achieved with Fe0, Bi/Fe0-1 [1% (w/w) of Bi], Bi/Fe0-3 [3% (w/w) of Bi], Bi/Fe0-5 [5% (w/w) of Bi], and Bi/Fe0-8 [8% (w/w) of Bi], respectively. Further improvements in the degradation efficiency of CHP were observed by combining the peroxymonosulfate (HSO5-) with Bi/Fe0-5 (i.e., 81% by Bi/Fe0-5 and 98% by the Bi/Fe0-5/HSO5- system at 8 min of treatment). Interestingly, both Fe0 and Bi/Fe0-5 showed effective H2 production under dark conditions that reached 544 and 712 μM by Fe0 and Bi/Fe0-5, respectively, in 70 mL of aqueous solution containing 0.07 g (i.e., at 1 g L-1 concentration) of the catalyst at ambient temperature