Fabrication of zinc oxide nanorods for photocatalytic degradation of docosane, a petroleum pollutant, under solar light simulator

The use of advanced oxidation processes (AOP) in photocatalysis is critical for treating hazardous chemical compounds in oil-produced water (OPW). ZnO NRs are one of the most important modern and safe photocatalysts and have been easily prepared by a microwave-assisted hydrothermal method and grown on glass substrates. Hexagonal-shaped ZnO NRs and a bandgap energy (Eg) of up to 3.2 eV were characterized using SEM, XRD, UV-Vis, and PL devices, respectively. The effectiveness of photocatalytic degradation on the organic docosane solution was evaluated using a solar light simulator. On the surface area of the ZnO NRs, high photon absorption causes e-/h+ pairs to be excited between the VB and CB, producing free radicals that immediately react with organic contaminants and transform them into harmless chemicals. The photocatalytic degradation efficiency of the compound docosane analysed using GC-MS/MS reached 68.5% at 5 hours of irradiation. A mechanism for the photocatalytic degradation of docosane was proposed at pH ∼ 6.5, and a reduction of 60.5% of the total organic carbon (TOC) was achieved. Thus, the photocatalytic treatment of organic compounds contained in OPW has great potential and serves an important environmental purpose.

Theoretical investigations on electronic structure and optoelectronic properties of vinyl fused monomeric and oligomeric benzimidazole derivatives using DFT and TDDFT techniques

CONTEXT

The present work encompasses the theoretical investigation of 14 benzimidazole-based (seven vinyl fused monomeric benzimidazole (VFMBI) and seven vinyl fused oligomeric benzimidazole (VFOBI)) derivatives using density functional theory (DFT) and time-dependent density functional theory (TD-DFT) techniques. The effects of electron donor and acceptor groups on the electronic structure such as HOMO (highest occupied molecular orbital) and LUMO (lowest unoccupied molecular orbital) energies, HOMO-LUMO energy gap, ionization potentials (IPs), electron affinities (EAs), internal reorganization energies of holes and electrons (λh/e), and excited state properties have been explored in the present work. In addition, natural bond orbital (NBO) analysis of these compounds has been investigated to reveal the typical stabilization interactions in these molecules. Hence, the aim of the present work is to explore the electronic structures and optoelectronic properties of the title molecules on the basis of the DFT quantum chemical calculations and to make an idea on the parameters influencing the optoelectronic efficiency toward a better understanding of the structure-property relationships. Moreover, the calculated results reveal the suitable optoelectronic properties of benzimidazole oligomer derivatives using theoretical techniques. Of the investigated molecules, 4_MABIMCY and 4_MABIOCY show potential optoelectronic properties and can be used as a potential charge transport material due to their narrow band gap, high hyperpolarizability, low ionization potential, and high electron affinity. The larger λab and λem values favor the system to be used as a potential optoelectronic material with better optical properties.

METHODS

All quantum chemical calculations were carried out using Gaussian09 theoretical chemistry code. Ground state calculations were made using the B3LYP/6-31+G(d,p) method. All excited state calculations had been computed using TDB3P86/6-311++(d,p). The initial structure for excited state calculations was optimized using the AM1 semi-empirical method.

Performance of Natural Coagulants on Greywater Treatment

Background:

Reusing waste water by appropriate treatment is an effective method for substantiating the ever increasing water demand for construction, irrigation, domestic and industrial purposes. The greywater is the domestic waste water that does not contain the toilet effluent and it is converted and used for non-potable purpose through coagulation and flocculation by using natural coagulant.

Objective:

The main objective of this work is to evaluate the coagulating efficiencies of various natural coagulants on synthetic greywater by varying pH, mixing speed, mixing time and coagulant dosage.

Methods:

Powdered coagulants obtained from tamarind seeds, moringa oleifera, banana peels and fly ash were compared with conventional commercial coagulants like alum for synthetic and real greywater.

Results:

The natural coagulants have shown significant performance compared to chemicals like alum.

Conclusion:

The turbidity removal efficiency for tamarind seeds, moringa oleifera, banana peels and fly ash were found to be 61.33%, 85.75%, 90.42%, 94.27% against 96.49% obtained from alum on treating with synthetic grey water under identical conditions.

Biodegradation of perchlorate from real and synthetic effluent by Proteobacterium ARJR SMBS in a stirred tank bioreactor system

The present work is a laboratory-scale study of perchlorate degradation using Proteobacterium ARJR SMBS in a stirred tank bioreactor (STBR). Anaerobically grown cultures of ARJR SMBS exposed to a variety of ClO4(-) levels within the range 30 to 150 mg L(-1) under anoxic conditions have been studied. The chloride released was measured and the average value found to be 43.55 mg L(-1). The average daily value of perchlorate degradation rate in this system was 17.24 mg L(-1) at optimum pH 7.5 and 0.25% NaCl salinity. The mixed liquor suspension solids of the system gradually increased from 0.025-0.156 g L(-1) during the operating period of 55 days. Mass balance indicated that the chloride produced was 0.45 mole per mole of perchlorate. The salinity of the system varied from 2.50-18.46 g L(-1), dependent primarily upon the inlet perchlorate concentration. The degradation mechanism, which obeyed a first-order substrate-utilizing kinetic model, allowed the growth rates and the half-saturation constants to be determined. The maximum observed anoxic growth rates (0.83-1.2 h(-1)) for ARJR SMBS in a synthetic effluent (SE) were considerably higher than in real effluent (RE) (0.45-0.59 h(-1)). The biomass yield of ARJR SMBS in STBR was higher in SE (1 +/- 0.4 mg L(-1)) than in RE (1 +/- 0.1 mg L(-1)). From the experimental findings, the uptake of perchlorate by the bacterium is suggested to be a non-interfacially-based mechanism. Under steady state operating condition the performance of the reactor was comparatively lower for RE than for SE but still offers significant control over the degradation of perchlorate under full-scale conditions.

N-[Morpholino(phen-yl)meth-yl]benzamide

The title compound, C₁₈H₂₀N₂O₂, crystallizes with two mol­ecules in the asymmetric unit. The morpholine rings of both mol­ecules adopt chair conformations. The crystal structure is stabilized by inter­molecular N—H⋯O hydrogen bonds. One phenyl ring is disordered over two orientations in a 0.665 (5):0.335 (5) ratio.