Doped graphitic carbon nitride (g-C3N4) catalysts for efficient photodegradation of tetracycline antibiotics in aquatic environments

Tetracyclines (TCs) antibiotics are very common and often used in both human and veterinary medicines. More than 75% of TCs are excreted in an active condition and released into the environment, posing a risk to the ecosystem and human health. Residual antibiotics are in global water bodies, causing antibiotic resistance and genotoxicity in humans and aquatic organisms. The ever-increasing number of multi-resistant bacteria caused by the widespread use of antibiotics in the environment has sparked a renewed interest in developing more sustainable antibiotic degradation processes. In this regard, photodegradation technique provides a promising solution to resolve this growing issue, paving the way for complete antibiotic degradation with the generation of non-toxic by-products. As a fascinating activity towards visible light range shown by semiconductor, graphitic carbon nitride (g-C₃N₄) has a medium bandgap, non-toxicity, chemically stable complex, and thermally great strength. Recent studies have concentrated on the performance of g-C₃N₄ as a photocatalyst for treating wastewater. Pure g-C₃N₄ exhibits limited photocatalytic activity due to insufficient sunlight usage, small surface area, and a high rate of recombination of electron and hole ([Formula: see text] & [Formula: see text]) pairs created in photocatalytic activity. Doping of g-C₃N₄ is a very effective method for improving the activity as element doped g-C₃N₄ shows excellent bandgap and electronic structure. Doping significantly broadens the light-responsive range and reduces recombination of e^- & h⁺ pairs. Under above context, this review provides a systematic and comprehensive outlook of designing doped g-C₃N₄ as well as efficiency for TCs degradation in aquatic environment.

Noble metal-free doped graphitic carbon nitride (g-C3N4) for efficient photodegradation of antibiotics: progress, limitations, and future directions

Graphitic carbon nitride (g-C₃N₄) is well recognised as one of the most promising materials for photocatalytic activities such as environmental remediation via organic pollution elimination. New methods of nanoscale structure design introduce tunable electrical characteristics and broaden their use as visible light-induced photocatalysts. This paper summarises the most recent developments in the design of g-C₃N₄ with element doping. Various methods of introducing metal and nonmetal elements into g-C₃N₄ have been investigated in order to simultaneously tune the material's textural and electronic properties to improve its response to the entire visible light range, facilitate charge separation, and extend charge carrier lifetime. The degradation of antibiotics is one of the application domains of such doped g-C₃N₄. We expect that this research will provide fresh insights into clear design methods for efficient photocatalysts that will solve environmental challenges in a sustainable manner. Finally, the problems and potential associated with g-C₃N₄-based nanomaterials are discussed. This review is expected to encourage the ongoing development of g-C₃N₄-based materials for greater efficiency in photocatalytic antibiotic degradation.

An enhanced method for the removal of methyl violet dye using magnetite nanoparticles as an adsorbent: Isotherm, kinetic and thermodynamic study

A green method has been developed using Gilloy (Tinospora Cordifolia) shoot extract to synthesize magnetic nanoparticles (MNPs). A further modification of MNPs was performed using anionic surfactant sodium dodecyl sulphate (SDS), to remove cationic dye methyl violet (MV) efficiently from the solution. As an adsorbent, SDS modified MNPs (SDS-MNPs) were tested for their ability to remove MV dye. Synthesized MNPs were characterized by ultra violet-visible spectroscopy (UV-VIS), X-ray diffraction spectroscopy (XRD), Fourier transform infrared spectroscopy (FT-IR), and scanning electron microscopy (SEM). In batch adsorption experiments, the effect of adsorbent dosage, initial dye concentration, time, and pH was evaluated. The maximum adsorption capacity of the adsorbent for MV dye was found to be 174.2 mg g^-1. The adsorption of dye onto the adsorbent followed Langmuir's isotherm. It was shown that the adsorption kinetics of dyes obeyed pseudo-second-order kinetics. Using thermodynamic parameters, spontaneous and exothermic adsorption was determined. As synthesized nanoparticles are magnetic in nature, regeneration and reusability of MNPs were investigated.

Aerobic sequential batch reactor for domestic sewage treatment: parametric optimization and kinetics studies

Domestic sewage (DS) was first treated in aerobic sequential batch reactor (SBR). In order to increase the treated water quality, DS from SBR was further treated using electrocoagulation (EC) and Ion exchange (IE) process. In the SBR study, process parameters such as hydraulic retention time (HRT) and reactor fill time (t f ) was optimized at various volume exchange ratio (VER) of 0.534, 0.4, 0.266, and 0.133. The best HRT and t f were observed to be 0.78 day (d) and 2 h, respectively, providing 72.37% chemical oxygen demand (COD) reduction (initial value of COD = 270 mg/dm3). Kinetics of biodegradation in SBR was also studied. The second stage treatment was performed in EC reactor at 1 ampere (A) current for 30 min electrolysis time (t R). EC reactor, further reduced COD and biological oxygen demand (BOD) up to 72 and 21 mg/dm3 from its average initial COD and BOD of 94 and 23 mg/dm3, respectively. Second stage treatment in IE process reduced hardness, sulphate, and phosphate up to 15, 0.05, and 0.13 mg/dm3 from its initial value 350, 5.48 and 1.16 mg/dm3, respectively. The treated water can be used as potable water after disinfection as its water quality is near to river water.

Biodegradation of acid red 3BN dye in sequential batch reactor: parameters and kinetics studies

Textile and dye industries generate wastewater which is considered as highly polluted and carcinogenic. Due to this, treatment of wastewater is required earlier to discharge or recycle. In the present studies, treatment of dye bearing water (DBW) has been explored. The treatment was performed using activated sludge (mixed culture) for aerobic process in sequential batch reactor (SBR). The fill volume (V F) and fill time (t F) variation in the treatment of DBW was taken place. The initial value of dye concentration, chemical oxygen demand (COD), sludge, and hydraulic retention time (HRT) were found to play important role in the treatment. At optimum condition (HRT = 2.5 d), the 86.84% COD reduction of 190 mg/L COD, and 92.33% dye reduction of 339 mg/L dye were achieved. These values are equal to overall 94.85% dye reduction of 500 mg/L, and 93.15% COD reduction of 380 mg/L. As a result, 500 mg/L dye was reduced to 26 mg/L, and 380 mg/L COD was reduced to 25 mg/L. The biodegradation fitted to Monod kinetics, for which kinetics parameter values of specific growth rate constant of biomass µ = 0.0047 h−1, yield coefficient (Y) = 1.059, and substrate utilization rate (q) = 0.0044 h−1 were evaluated at HRT = 2.5 d. The results show, this process can be applied to treat Acid Red 3BN Dye Water (AR3BNDW).

Acclimatization studies for degradation of Acid Red 3BN dye and its treatment in moving bed biofilm reactor

In this study, acclimatization of microorganisms for the degradation of Acid Red 3BN dye bearing water (AR3BNDW) using activated sludge was performed in a cylindrical aerobic reactor. The initial value of chemical oxygen demand (COD), dye, and mixed liquor suspended solids (MLSS) of activated sludge were evaluated as 870.5, 80.6 and 1200 mg/L The experiments were performed at ambient temperature (25–35 °C) and the stabilization was achieved at 15 d. Maximum reduction of chemical oxygen demand (COD) and color were observed to be 94.2%, and 91% after 15 d of acclimatization. After completion of acclimatization process, degradation of dye was studied in moving bed biofilm reactor (MBBR). In the process, 38, 50, 68 and 76% color reduction were achieved with polymer carrier fill ratio (FR) of 40, 50, 60 and 70%, respectively in 24 h. For effluent flow rate of 180, 240, 300 and 360 mL/h, respectively, the dye reductions of 76, 60, 48 and 36% and COD reductions of 72, 58, 46 and 34% were achieved in 24 h

Unification electrocoagulation-adsorption treatment for removal of COD and surfactant from automobile wastewater

The automobile sectors are an essential field of the service provider circle. The principal eminent impact identified with the vehicle service workshops, is the discharge of used surfactant, engine oil, and washed water into the surface and water bodies. In this context, this study’s objective is to treat the automobile wastewater by unified/combined electrocoagulation-adsorption (ECA) to achieve the permissible removal limits of COD and surfactant. ECA treatment experiments were conducted by varying adsorbent dose, mixing time, and electrolysis time using Box Behnken design model. By performing experiments, the optimum conditions were statistically obtained at ECA time of 25 min, mixing speed of 465 rpm, and adsorbent dosage of 1.81 mg/L for 71.58% COD removal and 77.91% surfactant removal. The outcomes show that the experimental results of this investigation were in good agreement with the model predictions.

Degradation of trypan blue dye using neutralized red mud in circulating fluidized bed reactor and its kinetics study

Dye is a common pollutant present in many chemical industrial waste water. Advanced oxidation processes are widely used for dye degradation. In this study, the degradation of trypan blue dye was examined by Fenton process. Neutralized red mud catalyst was used as a source of ferrous ion for Fenton’s process. The dye degradation performance has been analyzed by using circulating fluidized-bed reactor. The influence of some key parameters such as pH, initial dye concentration, catalyst dosage and hydrogen peroxide concentration on the degradation of dye has been investigated. All the experiments were performed for 90 min. The initial dye concentration was taken as 1.56 × 10−5 and 2.60 × 10−5 mol L−1 and the amount of catalyst was varied from 0.5 to 0.7 gm/L. The hydrogen peroxide was taken in the ratio of 1:20 with the catalyst. The effect of pH was studied in the varying range from 3–5. It was found that the more the acidic pH, more will be the rate of degradation. The increase in pH results in the lower degradation rate. As the amount of catalyst was increased, the degradation rate got increased. The optimized results were obtained at pH 3, catalyst dosage of 0.7 gm/L and dye concentration of 1.56 × 10−5 mol L−1. Subsequently, the reaction kinetics of Fluidized-bed reactor was also studied.

Dataset on statistical reduction of COD by electrocoagulation process using RSM

Viable and low treatment cost is a challenge for municipal wastewater, therefore, an efficient and cost effective electrocoagulation (EC) process was studied to treat domestic sewage (DS) in laboratory batch process using SS-304 as electrode material. Effects of various parameters like pH, current density (CD), electrode configuration in numbers and treatment time (t_R) were tested to find optimum operating condition for COD and other pollutants removal. The experiments were also planned to optimize the operating parameters through response surface methodology (RSM) based central composite design (CCD) which gave 77.78% COD reduction at CD = 27.78 A/m² and t_R = 20 min respectively.

Modeling and optimization data analysis on photocatalytic decolourization of amido black 10B using ZnO catalyst

This article contains the experimental and statistical data related to decolourization of Amido Black 10B using photocatalytic process. Box-Behnken experimental design (BBD) has been used to study the influence of operational parameters on photocatalytic oxidation of Amido Black 10B by using zinc oxide (ZnO) as a catalyst. This data set presents a concise description of experimental conditions for variable factors such as initial dye concentration of 100 ppm, oxidant dosage 20 mMol/L and catalyst dose 1g/L at natural pH for 4 hr of reaction time in presence of 12W intensity ultra-violet radiation were optimized for over a response parameter, decolorization efficiency of Amido Black 10B. The effects of decolorization on process variables were investigated by developing a mathematical model, results indicated that ZnO can be used as an efficient catalyst for the decolorization of Amido Black 10B. Analysis of variance (ANOVA) showed a high coefficient of statistical measure value (R² = 0.9915) and prediction of the driven regression model was found to be satisfactory.

Outbreak of enteric fever due to Salmonella Paratyphi A variety durazzo (2,12:a:-) in a hilly region of North India: A report of 43 cases

Enteric fever due to Salmonella Paratyphi A (SPA) is a global problem occurring as outbreaks at times. An unusual SPA (2,12:a:-) variety durazzo has been reported rarely. We report an outbreak of enteric fever due to this variety affecting 43 individuals. The blood samples grew unusual mucoid, lactose non-fermenting colonies with atypical biochemical reactions in sugar fermentation and amino acid decarboxylation. Isolates had sensitivity to ceftriaxone, chloramphenical, cotrimoxazole, intermediate susceptibility to ciprofloxacin and resistance to ampicillin and nalidixic acid. Identification was confirmed as SPA (2,12:a:-) at the National Salmonella Centre.

Detecting mutation pattern of drug-resistant Mycobacterium tuberculosis isolates in Himachal Pradesh using GenoType(®) MTBDRplus assay

CONTEXT

Tuberculosis (TB) is a major public health problem in India and a principal cause of death in adults, especially among the economically productive age group. India accounts for one-fifth of the global burden of TB. It is estimated that about 40% of Indian population is infected with TB bacillus. The GenoType® MTBDRplus molecular method allows rapid diagnosis of the clinical samples and detection of the most common mutations in the genes associated with rifampicin (R) and isoniazid (H) resistance.

AIMS

To study the drug resistance and mutational patterns in multidrug-resistant (MDR) suspects clinical strains using GenoType® MTBDRplus assay.

SUBJECTS AND METHODS

A total of 770 sputum samples of the MDR-TB suspects were included in this study, which were received at Intermediate Reference Laboratory, Government TB Sanatorium, Dharampur, Solan, Himachal Pradesh from the Designated Microscopy Centres of Himachal Pradesh for the culture and susceptibility testing. All the 521 Mycobacterium tuberculosis complex (MTBC) strains were subjected to GenoType® MTBDRplus (HAIN Lifescience) assay to detect molecular resistance pattern to first line anti-tubercular drugs (isoniazid and rifampicin).

RESULTS

Of 770 samples, 556 (72.20%) were from male and 214 (27.80%) were from female. Among the 521 MTBC strains, 19.76% were found to be MDR and mono-resistance to isoniazid and rifampicin was detected in 8.63% and 6.14% strains respectively. About 74.81%, 76.35% and 5.40% strains harboured known mutation in rpoB, katG and inhA genes respectively.

CONCLUSIONS

In rpoB gene, the most common mutation is associated with S531 L region. The GenoType® MTBDRplus assay is a rapid test for the detection of the most common mutations in MDR-TB strains. In our study, unknown rpoB gene mutations were found in 25.18% strains that may further be detected by gene sequencing.

Aerobic degradation of petroleum refinery wastewater in sequential batch reactor

The aim of the present work was to study the effect of various parameters affecting the treatment of raw petroleum refinery wastewater (PRW) having chemical oxygen demand (COD) of 350 mg L(-1) and total organic carbon (TOC) of 70 mg L(-1) in sequential batch reactor (SBR). Effect of hydraulic retention time (HRT) was studied in instantaneous fill condition. Maximum COD and TOC removal efficiencies were found to be 80% and 84%, respectively, for fill phase of 2 h and react phase of 2 h with fraction of SBR being filled with raw PRW in each cycle being 0.4. Effect of parameters was studied in terms of settling characteristic of treated slurry. Kinetics of treatment process has been studied. FTIR and UV-visible analysis of PRW before and after treatment have been performed so as to understand the degradation mechanism.

Comparative Studies on Nitrophenol Removal byAdsorption and Simultaneous Adsorption-Biodegradation Processes

In this paper, it was aimed to study the removal of 4-nitrophenol (NP) from aqueous solution by adsorption using granular activated carbon (GAC); and in sequencing batch reactor (SBR) without any adsorbent (blank-SBR) and with an SBR loaded with GAC (GAC–SBR). During adsorption study with GAC, effect of pH, adsorbent dose (m) and contact time (t) were studied. Adsorption isotherm, kinetic and thermodynamic parameters were determined. During NP removal in SBR, effect of hydraulic retention time (HRT), initial concentration (C 0) and m were studied. The percent removal in case of GAC–SBR was found to be greater in comparison to blank-SBR. The removal of NP from blank-SBR and GAC–SBR for C 0 of 35, 65 and 100 mg/l was found to be 90.46% and 91.23% (m=2 g/l); 52.33% and 96.05% (m=2.5 g/l); 20.01% and 92.72% (m=2.5 g/l), respectively.

Total serum levels of triiodothyronine (T3) thyroxine (T4) and thyrotropine (TSH) in school going children of Dibrugarh district: an endemic goitre region of Assam

The Thyroid Status was studied by estimating the total serum levels of T3 and T4 by radioimmunoassay (RIA) and TSH by radioimmunometric Assay (IRMA) from 635 school children (8-20 years; male 129, female 506) of the Dibrugarh district: a chronic endemic goitrous region of India. The results were compared with the control group of 147 (male 48, female 99) of healthy medical students of the same geographical area. The average values of T3 and TSH of school children were found higher and T4 lower than the control; the difference were only significant for T3 and TSH. T3/T4 ratio is more in school children than the control. The findings of low T4 and high TSH indicate that the school children (Pubertal stage) from chronic iodine deficients areas suffer from poor thyroid status; the male seemed to have been affected more than the female. As age advances the thyroid status improves in female.

Diagnosis of symptomatic visceral leishmaniasis by use of the polymerase chain reaction on patient blood

To diagnose symptomatic visceral leishmaniasis (kala-azar) using peripheral blood rather than tissue aspirates, a polymerase chain reaction (PCR) technique was developed for which the detection limit is 1 Leishmania-infected macrophage in 8 mL of blood. For Indian, Kenyan, or Brazilian patients with parasitologically confirmed kala-azar, 57 of 63 cases before treatment had blood that was PCR-positive (90% sensitivity). None of 40 clinically healthy persons had PCR-positive blood (100% specificity). Twelve (92%) of 13 clinically cured Indian patients had negative PCR reactions 1-6 months after treatment. This PCR procedure can provide a parasitologic diagnosis for the vast majority of kala-azar cases before therapy, may identify patients who have been successfully treated by chemotherapy, and should substantially reduce the need for invasive tests.