Exploring the twin potential of nanostructured TiO2:SeO2 as a promising visible light photocatalyst and selective fluorosensing platform.

The present work describes the development of TiO2/SeO2 nanostructure as a potential candidate for visible light photocatalysis as well as selective fluorophore for the sensing of picric acid. The obtained nanostructure consists of uniform globular nanoparticles having approximate size of 170 nm and possess an optical band gap of 2.33 eV with absorption maxima at 473 nm. The photocatalyst was able to achieve 90.34% degradation efficiency for 2, 4-dichlorophenol (2,4-DCP) with rate constant of 0.0046 min-1 in the visible region. Further the nanostructure was able to serve as a selective fluorophore for sensing of Picric acid portraying more than 95% of fluorescence quenching when the concentration of PA is 10-4 M. Theoretical calculations indicate the interaction of organic pollutants with the nanostructure and reveal that both picric acid (- 66.21 kcal/mol) and 2,4-DCP (- 12.31 kcal/mol) possess more negative binding energy values demonstrating a strong interaction of both with the nanostructure, making it suitable for the degradation as well as sensing of organic pollutants. Thus this study explains the potential of prepared catalyst for waste water treatment.

A Zn/Cd/Ni Metal-Organic Framework-Based Solid and Flexible Fluoroprobes for Highly Selective Detection of 4-Nitroaniline in Real Water Samples.

The combination of diazabicyclic compound i.e. 1,4-diazabicyclo[2.2.2]octane (DABCO) and dicarboxylate linker 1,4-dicarboxylic acid are employed to self-assemble with three divalent metal ions such as Zn2+, Cd2+, Ni2+ led to the formation of highly stable pillar layered luminescent metal-organic frameworks. The emissive response of as-synthesized MOFs was studied in organic solvents with different functionalities resulting in the development of fluoroprobes having excellent recognition ability for 4-nitroaniline with detection limit upto micromolar. All the MOFs display a good linear relation between the fluorescence intensity and concentration of 4-NA in the range of 10-90 µmol L-1. The values of Ksv for Zn-MOF, Cd-MOF, and Ni-MOF are found to be 1.75 × 104 mol-1L, 1.25 × 104 mol-1L, and 28.0 × 104 mol-1L, respectively. The calculated detection limit values are 19.7 µmol L-1, 27.6 µmol L-1, and 1.19 µmol L-1 respectively. Moreover, the study was further extended to fabricate the solid membrane-based fluoroprobe using a linear chitosan polysaccharide and act as an efficient solid fluoroprobe for the detection of 4-NA. This proposed synthesis of polymeric membrane facilitates the MOF@chitosan fluorophore to transfer its fluorescence-emissive nature to a solid state.

Biopolymer templated strategized greener protocols for fabrication of ZnO nanostructures and their application in photocatalytic technology for phasing out priority pollutants.

Zinc oxide (ZnO) nanostructures have been successfully synthesized via template-assisted and template-free route using three different synthetic methods, i.e., sonochemical, mechanochemical, and hydrothermal. Biopolymer xanthan gum (XG) served as sacrificial template for ZnO synthesis as provided the surface for the growth of nanostructures in a controlled manner. The employment of multifarious synthetic techniques resulted in fabrication of ZnO nanoparticles with diverse morphologies such as needle shaped, hexagonal, and spherical particles. Further, the template-assisted protocols generated thermally stable highly crystalline nanostructures along with high surface area, larger pore size, and low band gap energies in contrast to template-free protocol. The structural and other physicochemical studies were manifested by XRD, N2 adsorption desorption, FESEM, TGA, and UV-Vis spectral analysis. The template-assisted ZnO nanostructures were explored as a potential photocatalyst for the catalytic degradation of emerging pollutants, i.e., triclosan (TCS) and imidacloprid (IMD) under the exposure of UV light. The products formed during the photocatalytic reaction were monitored by UV-Vis spectroscopy and HPLC. The results obtained revealed the high catalytic efficiency of ZnO synthesized via template-assisted sonochemical method for TCS (99.60%) and IMD (96.09%) which is attributed to the high surface area and lower band gap energy of the catalyst. The high catalytic potential of the sonochemically synthesized ZnO also substantiated from the kinetic data as high-rate constant was obtained. Thus, the template-assisted protocols developed led to preparation of nanostructures having tailored properties for efficient photocatalysis and can rapidly degrade selected emerging contaminants such as personal care products and organophosphate pesticides. Hence, environment-friendly synthesized photocatalyst can be appropriately employed to wastewater treatment contaminated with emerging pollutants.

Development of an azo functionalized oligomeric chitosan sensor for rapid visual, spectrophotometric and spectrofluorometric detection of KMnO4 up to micromolar concentrations.

A water-soluble azo functionalized oligomeric chitosan reagent (ß-NAC) has been developed for the visual detection and quantification of KMnO4 at micromolar concentrations. The ß-NAC sensor was also explored as a detection probe for the spectrophotometric and spectrofluorometric detection of several metal ions and anions. The synthesized reagent was characterized by TGA-DTA-DTG analysis, DLS studies, BET analysis, and spectral analysis. The ß-NAC reagent produces conspicuous colours with different concentrations and different pH values of KMnO4 solution. This provides evidence for high selectivity in the visual detection of KMnO4 up to the micromolar level because of its interactions in the case of KMnO4 only. The colour of the ß-NAC reagent after interacting with KMnO4 (10-3 M) changes from brown to blood red. Furthermore, the ß-NAC sensor was employed for the spectrophotometric detection of KMnO4. The absorption spectrum of ß-NAC shows a peak at 327 nm and on interacting with KMnO4, it shows a bathochromic shift to 331 nm. The intensity of the peak at 331 nm increases as the concentration of KMnO4 was increased from 1 µM to 0.01 M. The detection and quantification limits in the spectrophotometric detection of KMnO4 were found to be 4.55 µM and 15.17 µM, respectively. The results of pH studies show that there is a pH effect of the KMnO4 solution on KMnO4 detection. The stability of the complex was determined by investigating the effect of time on the absorption intensity. In the spectrofluorometric detection, the fluorescence intensity of ß-NAC at the 427 nm emission maxima was decreased on adding KMnO4 solution. The fluorescence quenching increased on increasing the KMnO4 concentration from 1 µM to 0.008 M. The optimum pH for fluorescence quenching was found to be 8. The detection and quantification limits in the spectrofluorometric detection of KMnO4 were found to be 0.967 µM and 3.223 µM, respectively. The Stern-Volmer constant value was found to be 41 366.2 L mol-1, confirming the significant complexation between KMnO4 and the ß-NAC reagent. Interference studies were conducted to analyse the effect of various metal ions and anions on KMnO4 detection. Electrochemical studies were also performed to analyse the mechanism of complex formation.

Bioactive phytosteroids from Araucaria columnaris (G. Forst.) Hook.: RP-HPLC-DAD analysis, in-vitro antioxidant potential, in-silico computational study and molecular docking against 3MNG and 1N3U.

Genus Araucaria is globally known for its medicinal, economic, and ornamental values. Most of its species have not been extensively studied yet for their chemical composition and biological activities. Therefore, the phytochemical investigation and antioxidant potential of Araucaria columnaris (G. Forst.) Hook. has been analyzed. This work aims to investigate the isolation, characterization, and antioxidant potential of bioactive compounds from the bark extract of the exemplar plant. Their structures were elucidated by virtue of physicochemical properties and spectroscopic methods. The antioxidant potential was further discussed through various assays including DFT and molecular docking. The isolation of pure compounds from bioactive extract has been carried out chromatographically. Their structures were elucidated by 1D, 2D NMR, FT-IR, UV, MS, and RP-HPLC-DAD data analysis. In vitro, the antioxidant potential was evaluated by the DRSC, FRAP, and TAC assays and in-silico studies by DFT and molecular docking. For the first time, pure compounds such as stigmasterol (IC1) and diosgenin (IC2) were isolated from the bark extract of Araucaria columnaris. In vitro antioxidant activity has been demonstrated that IC2 has higher values of DRSC, FRAP, and TAC than IC1, due to higher reactivity of IC2 than IC1 as represented by quantum reactivity parameters like lower energy gap, higher dipole moment, and higher electron-donor power. Further, antioxidant potential was also confirmed by molecular docking against two stress proteins such as 3MNG (IC2: -7.70 Kcal/mol > IC1: -7.32 Kcal/mol > ascorbic acid: -5.56 Kcal/mol) and 1N3U (heme: -12.42 Kcal/mol > IC2: -11.15 Kcal/mol > IC1: -9.45 Kcal/mol). In conclusion, the phytosteroids exhibited excellent antioxidant potential, which could enlighten their ethnomedical use. The exemplar plant offered powerful and available antioxidant besides significantly active phytoconstituents.

Persistence and biodegradation of quinalphos using soil microbes.

The present study reports the degradation of the persistent and toxic organophosphate, quinalphos, by employing microorganisms that were already members of the natural soil community for degradation. Bacillus and Pseudomonas spp., both of which are capable of degrading quinalphos from aqueous streams, were isolated from different contaminated soils. Batch experiments were performed to determine the natural and induced biodegradation of quinalphos in the aqueous medium. The rate of degradation was analyzed through determination of residual concentration using UV-Vis spectrophotometer and high-performance liquid chromatography. A single peak of a metabolite was observed on the 160th day, and identified as dihydroxy quinalphos oxon by mass spectrometry. The presence of quinalphos and its metabolite in water over an extended period prompted the authors to investigate its induced biodegradation using indigenous microbes extracted from soil. For biodegradation studies, the isolated microbes were inoculated into minimal media with quinalphos for 17 days. The results revealed that > 80% of quinalphos was degraded in 17 days in the presence of isolated microbes, and no metabolite was observed during the biodegradation process.

Coupling of solar-assisted advanced oxidative and biological treatment for degradation of agro-residue-based soda bleaching effluent.

This study evaluates the effect of integrated solar-assisted advanced oxidation process (AOP) and biological treatment on the extent of degradation of effluents from chlorination (C) and first alkaline extraction (E(1)) stages of soda pulp bleaching in agro-residue-based pulp and paper mill. Biodegradation of the effluents was attempted in suspended mode using activated sludge from the functional pulp and paper industry effluent treatment plant acclimatized to effluents in question. The photocatalytic treatment was employed using zinc oxide (ZnO) in slurry mode for decontamination of effluents in a batch manner and the degradation was evaluated in terms of reduction in chemical oxygen demand. The biological treatment (24 h) of C and E(1) effluent resulted in 30 and 57 % of degradation, respectively. Solar-induced AOP of C and E(1) effluents resulted in 53 and 43 % degradation under optimized conditions (2.5 g L(-1) ZnO at pH 8.0) after 6 h of exposure. For C effluent, a short duration of solar/ZnO (1 h) prior to biological treatment reduced the time required at biological step from 24 to 12 h for almost same extent (92 %) of degradation. However, sequential biological treatment (24 h) followed by solar/ZnO (2 h) resulted in 85.5 % degradation. In contrast, in the case of E(1) effluent, sequential biological (24 h)-solar/ZnO (2 h) system effectively degrades effluent to 95.4 % as compared to 84.8 % degradation achieved in solar/ZnO (2 h)-biological treatment (24 h) system. In the present study, the sequencing of photocatalysis with the biological treatment is observably efficient and technically viable process for the complete mineralization of the effluents.

Agricultural waste material as potential adsorbent for sequestering heavy metal ions from aqueous solutions - a review.

Heavy metal remediation of aqueous streams is of special concern due to recalcitrant and persistency of heavy metals in environment. Conventional treatment technologies for the removal of these toxic heavy metals are not economical and further generate huge quantity of toxic chemical sludge. Biosorption is emerging as a potential alternative to the existing conventional technologies for the removal and/or recovery of metal ions from aqueous solutions. The major advantages of biosorption over conventional treatment methods include: low cost, high efficiency, minimization of chemical or biological sludge, regeneration of biosorbents and possibility of metal recovery. Cellulosic agricultural waste materials are an abundant source for significant metal biosorption. The functional groups present in agricultural waste biomass viz. acetamido, alcoholic, carbonyl, phenolic, amido, amino, sulphydryl groups etc. have affinity for heavy metal ions to form metal complexes or chelates. The mechanism of biosorption process includes chemisorption, complexation, adsorption on surface, diffusion through pores and ion exchange etc. The purpose of this review article is to provide the scattered available information on various aspects of utilization of the agricultural waste materials for heavy metal removal. Agricultural waste material being highly efficient, low cost and renewable source of biomass can be exploited for heavy metal remediation. Further these biosorbents can be modified for better efficiency and multiple reuses to enhance their applicability at industrial scale.

Removal of cadmium (II) from aqueous solutions by adsorption on agricultural waste biomass.

This paper reports the feasibility of using various agricultural residues viz. sugarcane bagasse (SCB), maize corncob (MCC) and Jatropha oil cake (JOC) for the removal of Cd(II) from aqueous solution under different experimental conditions. Effect of various process parameters, viz., initial metal ion concentration, pH, and adsorbent dose has been studied for the removal of cadmium. Batch experiments were carried out at various pH (2-7), adsorbent dose (250-2000 mg), Cd(II) concentration (5-500 mg l(-1)) for a contact time of 60 min. The maximum cadmium removal capacity was shown by JOC (99.5%). The applicability of Langmuir and Freundlich isotherm suggests the formation of monolayer of Cd(II) ions onto the outer surface of the adsorbents. Maximum metal removal was observed at pH 6.0 with a contact time of 60 min at stirring speed of 250 rpm with an adsorbent dose of 20 g l(-1) of the test solution. The maximum adsorption of cadmium (II) metal ions was observed at pH 6 for all the adsorbents viz; 99.5%, 99% and 85% for JOC, MCC, and SCB, respectively. Order of Cd(II) removal by various biosorbents was JOC>MCC>SCB. JOC may be an alternative biosorbent for the removal of Cd(II) ions from the aqueous solution. FT-IR spectra of the adsorbents (before use and after exhaustion) were recorded to explore number and position of the functional groups available for the binding of Cd(II) ions on to studied adsorbents. These results can be helpful in designing a batch mode system for the removal of cadmium from dilute wastewaters.

Removal of nickel(II) from aqueous solution by adsorption on agricultural waste biomass using a response surface methodological approach.

In the present study, effect of adsorbent dose, pH and agitation speed on nickel removal from aqueous medium using an agricultural waste biomass, Sugarcane bagasse has been investigated. Batch mode experiments were carried out to assess the adsorption equilibrium. The influence of three parameters on the removal of nickel was also examined using a response surface methodological approach. The central composite face-centered experimental design in response surface methodology (RSM) by Design Expert Version 6.0.10 (Stat Ease, USA) was used for designing the experiments as well as for full response surface estimation. The optimum conditions for maximum removal of nickel from an aqueous solution of 50 mg/L were as follows: adsorbent dose (1500 mg/L), pH (7.52) and stirring speed (150 rpm). This was evidenced by the higher value of coefficient of determination (r(2)=0.9873).

Removal of hexavalent chromium from aqueous solution by agricultural waste biomass.

In the present study adsorption of Cr(VI) from aqueous solutions onto different agricultural wastes, viz., sugarcane bagasse, maize corn cob and Jatropha oil cake under various experimental conditions has been studied. Effects of adsorbent dosage, Cr(VI) concentration, pH and contact time on the adsorption of hexavalent chromium were investigated. The concentration of chromium in the test solution was determined spectrophotometrically. FT-IR spectra of the adsorbents (before use and after exhaustion) were recorded to explore number and position of the functional groups available for the binding of chromium ions on to studied adsorbents. SEMs of the adsorbents were recorded to explore the morphology of the studied adsorbents. Maximum adsorption was observed in the acidic medium at pH 2 with a contact time of 60min at 250rpm stirring speed. Jatropha oil cake had better adsorption capacity than sugarcane bagasse and maize corn cob under identical experimental conditions. The applicability of the Langmuir and Freundlich adsorption isotherms was tested. The results showed that studied adsorbents can be an attractive low cost alternative for the treatment of wastewaters in batched or stirred mode reactors containing lower concentrations of chromium.

Inhibition of nitrification in soil by metal diethyldithiocarbamates.

Nitrification acts as a key process in determining fertilizer use efficiency by crops as well as nitrogen losses from soils. Metal dithiocarbamates in addition to their pesticidal properties can also inhibit biological oxidation of ammonium(nitrification) in soil. Metal [M = V(III), Cr(III), Mn(II), Fe(III), Ni(II), Cu(II), Zn(II) and Co(II)] diethyldithiocarbamates (DEDTC) were synthesized by the reaction of sodium diethyldithiocarbamate with metal chloride in dichloromethane/water mixture. These metal diethyldithiocarbamates were screened for their ability to inhibit nitrification at different concentrations( 10 microg/g soil, 50 microg/g soil and 100 microg/g soil). With increasing concentration of the complex, capacity to retard nitrification increased but the extent of increase varied for different metals. At 100 microg/g soil, different complexes showed nitrification inhibition from 22.36% to 46.45% . Among the diethyldithiocarbamates tested, Zn(DEDTC)2 proved to be the most effective nitrification inhibitor at 100 microg/g soil. Manganese, iron and chromium diethyldithiocarbamates also proved to be effective nitrification inhibitors than the others at 100 microg/g soil. The order of percent nitrification inhibition in soil by metal diethyldithiocarbamates was: Zn(II) > Mn(II) > Fe(III) > Cr(III) > V(III) > Co(II) > Ni(II) > Cu(II).