XPS valence band observable light-responsive system for photocatalytic acid Red114 dye decomposition using a ZnO-Cu2O heterojunction.

ZnO-Cu2O composites were made as photocatalysts in a range of different amounts using an easy, cheap, and environment-friendly coprecipitation method due to their superior visible light activity to remove pollutants from the surrounding atmosphere. X-ray diffraction and Fourier transform infrared spectroscopy (FT-IR) have demonstrated that ZnO-Cu2O catalysts are made of highly pure hexagonal ZnO and cubic Cu2O. X-ray photoelectron spectroscopy has confirmed that there is a substantial interaction between the two phases of the resultant catalyst. The optical characterizations of the synthesized ZnO-Cu2O composite were done via UV-vis reflectance spectroscopy. Due to the doping on ZnO, the absorption range of the ZnO-Cu2O catalyst is shifted from the ultraviolet to the visible region due to diffuse reflection. The degradation efficiency is affected by the Ratio of ZnO: Cu2O and ZnO-Cu2O composite with a proportion of 90:10 exhibited the most prominent photocatalytic activity on Acid Red 114, with a pseudo-first-order rate constant of 0.05032 min-1 that was 6 and 11 times greater than those of ZnO and Cu2O, respectively. The maximum degradation efficiency is 97 %. The enhanced photocatalytic activity of the composite is caused by the synergistic interaction of ZnO and Cu2O, which improves visible light absorption by lowering band gap energy and decreasing the rate at which the electron-hole pairs recombine. The scavenging experiment confirmed that hydroxyl radical was the dominant species for the photodegradation of Acid Red 114. Notably, the recycling test demonstrated the ZnO-Cu2O photocatalyst was highly stable and recyclable. These results suggest that the ZnO-Cu2O mix might be able to clean up environmental pollutants when it meets visible light.

Spatial distribution and hydrogeochemical evaluations of groundwater and its suitability for drinking and irrigation purposes in kaligonj upazila of satkhira district of Bangladesh.

Groundwater is a significant water resource for drinking and irrigation in Satkhira district, Bangladesh. The depletion of groundwater resources and deterioration in its quality are the results of the confluence of factors such as industrialization, intensive irrigation, and rapid population growth. For this reason, this study focused on the evaluation of tubewell water of six unions of Kaligonj upazila in Satkhira district, which is situated in the coastal southwest part of Bangladesh. Major and trace elemental concentrations were assimilated into positive matrix factorization (PMF) to identify potential sources and their respective contributions. Principal component analysis (PCA) revealed that groundwater salinization and manmade activities were the primary causes of heavy metals in the coastal groundwater. Its average pH value was found to be 7.5, while Dissolved oxygen, Total dissolved solids, salinity, and conductivity, with values ranging from 1.18 to 7.38 mg/L, 0.5-4.88 g/L, 0.4-5%, and 0.95 to 8.56 mS/cm, respectively. The total hardness average value was 561.7 mg/L, classified into the very hard water categories, which is why 90% of the tubewell water samples were unfit for household purposes. All samples had an excessive level of arsenic present. The iron concentration of fifteen (15) samples crossed the standard limit according to WHO 2011 value. Around 63% of the samples were of the Na+-K+-Cl--SO42- type, and about 72% were sodium-potassium and alkali types. 98% of samples were covered in chloride and bicarbonate. The findings showed that 45.83% of the groundwater samples had negative Chloroalkaline index (CAIs), while 54.16% had positive. The permeability index (PI) was an average of 73%, and residual sodium carbonate (RSC) averaged 260.2 mg/L, and the findings clearly showed that 80% of the samples weren't appropriate for irrigation. According to the sodium adsorption ratio (SAR) value, 65% of the samples fell into the unsuitable category. These calculations indicated a high overall salinity hazard in the study area, which may be caused by the intrusion of sea water given that the study area is close to the coastal region. Findings compared to standards revealed that the majority of the samples were deemed unfit for drinking and irrigation purposes. Hence, additional attention must be paid to this area to ensure the availability of drinkable water and to preserve sustainable farming practices.

Effect of successive recycling and reuse of acid liquor for the synthesis of graphene oxides with higher oxygen-to-carbon ratios.

Graphene has recently drawn exponential attention due to its surprising physicochemical properties and diversified field of applications. Although graphene oxides (GOs), itself is an exclusive material, it is also an intermediate product for the production of reduced graphene oxides (rGOs), graphene and their derivatives, which are other more superficial materials. In this study, GOs with higher oxygen to carbon ratios were synthesized following the Tour method, where the excess feed acid liquor (FAL) of mixed concentrated sulfuric and orthophosphoric acids at a ratio of 90:10 was recovered from the reaction slurries by applying the centrifugation technique. About 80-90 % of the FAL was recycled and reused as feed for the subsequent batches. The changes in the properties of FAL for the five consecutive recycling and reuse were studied. The properties of recycled FALs were investigated by measuring density, moisture content, pH, and ion concentration. The consecutive recycling of FALs tends to increase the moisture content about 0.5% in each recycles. Ion-chromatography (IC) was used to measure the variation in SO42- and PO43- ions in the FALs. The H2SO4 reacts with KMnO4 and crystalized out from the recovered FAL faster than the phosphoric acid. So, sulfuric acid content in the makeover FALs must be greater than primary FAL. The product GOs were characterized using FT-IR, FT-Raman, UVVis, STA, SEM, XPS, Zeta-potential, and particle size analyzers. The variation of the properties of GOs with the changes in the reaction parameters such as temperature and time were investigated and correlated with the product yield. It was observed that the effect of temperature on the reaction rate was found to be negatively and positive with the reaction time. The oxygen-to-carbon atomic ratio from XPS analysis was found 66.7%, which supported the increase in product yields 66.9% in the experimental results. The effect of acid concentration, reaction temperature, and time on the GOs properties were satisfactory, correlated, and easily controllable with the reaction conditions. A higher extent of oxidation and enhanced product yields 65-70% were observed at 60-70 °C and 14-18 h. A mixture of nano- and macro-molecular GOs was obtained, and their compositions were easily controllable and separable by controlling the reaction conditions. A correlation was made among the properties of synthesized GOs, FAL, and recycled FAL and reaction conditions.

Ultrafast and simultaneous removal of four tetracyclines from aqueous solutions using waste material-derived graphene oxide-supported cobalt-iron magnetic nanocomposites.

In this work, a graphene oxide-supported cobalt-iron oxide (GO/Co-Fe) magnetic nanocomposite was successfully synthesized using waste dry cells for the efficient and simultaneous removal of tetracycline (TC), chlortetracycline (CTC), oxytetracycline (OTC), and doxycycline (DTC) from aqueous solutions. The GO/Co-Fe nanocomposite was thoroughly characterized using Fourier transform infrared spectroscopy, vibrating sample magnetometry, X-ray diffraction, field emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and zeta potential analysis. This multi-faceted characterization provided clean insights into the composition and properties of the synthesized nanocomposite. The adsorption of tetracyclines (TCs) was systematically investigated by assessing the influence of critical factors, such as adsorbent dosage, contact duration, initial pH of the solution, initial concentration, and temperature. The GO/Co-Fe adsorbent showed high removal efficiencies of 94.1% TC, 94.32% CTC, 94.22% OTC, and 96.94% DTC within 30 s contact period. The maximum removal efficiency of TCs was found at a low adsorbent dose of 0.15 g L-1. Notably, this superior removal efficiency was achieved at neutral pH and room temperature, demonstrating the adsorbent's efficacy under environmentally viable conditions. The kinetic studies demonstrated that the adsorption process was fitted satisfactorily with the pseudo-second-order model. Additionally, the adsorption behaviour of TCs on the GO/Co-Fe adsorbent was assessed by isotherm models, Langmuir and Freundlich. The experimental data followed the Langmuir isotherm, signifying a monolayer adsorption mechanism on the surface of the adsorbent. The adsorption capacities (qm) of GO/Co-Fe for TC, CTC, OTC and DTC were determined to be 64.10, 71.43, 72.46 and 99.01 mg g-1, respectively. Importantly, the GO/Co-Fe adsorbent showed reusability capabilities. The super magnetic properties of GO/Co-Fe made it easy to use for several cycles. These results clearly establish GO/Co-Fe as an exceptionally effective adsorbent for the removal of TCs from aqueous systems, highlighting its great potentiality in water treatment applications.

Antioxidant activity study and GC-MS profiling of Camellia sinensis Linn.

The antioxidant activity of tea leaves extract is a widely researched topic. Tea leaves, particularly those from the Camellia sinensis Linn plant, have garnered attention due to their potential health benefits attributed to their antioxidant properties. Antioxidants are compounds that can neutralize harmful free radicals in the body, which can damage cells and contribute to various health issues, including cancer, cardiovascular diseases, and aging. In this research, the matured tea leaves which has been considered as agricultural waste in Moulovibazar area of Bangladesh have been investigated as a potential source of antioxidant. Methanol was used as solvent for the extraction of antioxidant. DPPH (1,1-diphenyl-2-picryl hydrazyl) scavenging free radical assay method was used to assess the antioxidant activity of the extracts and ascorbic acid was used as positive control. Gas chromatography with mass spectrometric (GC-MS) analysis method was conducted on this extract to investigate the principal components. The half inhibitory concentration (IC50) values of methanol extract and ascorbic acid were found to be 69.51 µg/mL and 10.70 µg/mL, respectively. Caffeine is the main compound (74.47%) among the eight bioactive compounds was identify and quantified by GC-MS.

Assessment of heavy metals migrated from food contact plastic packaging: Bangladesh perspective.

Plastic-based food-contact materials are potentially threatening the environment and public health by releasing toxic heavy metals. This study aimed to identify the types of plastic commonly used in Bangladesh as food-contact materials (FCMs) and assess the migration of heavy metals from these FCMs. Plastic types were identified using attenuated total reflectance fourier transform infrared spectroscopy (ATR-FTIR), and 25 samples were selected based on the category, including Polyethylene Terephthalate (PET), Polyethylene (PE), Polypropylene (PP), Polystyrene (PS), and Polycarbonate (PC). Distilled water, 3% acetic acid, and 15% ethanol were used as food simulants to assess the overall migration of chemicals at 70 °C for 2 h. The concentrations of heavy metals (Pb, Cd, Hg, Cr, and Sb) were analyzed using an Atomic Absorption Spectrophotometer (AAS). Results revealed that the highest overall migration occurred in coffee cups measuring 3.50 ± 0.17 mg/kg (using water simulant) and in yogurt containers with a measurement of 9.17 ± 0.1 mg/kg (using 3% acetic acid). The highest concentrations of Pb, Cd, Hg, Cr, and Sb were found in PP-2 (0.45 ± 0.01 mg/kg), PP-2 (0.36 ± 0.01 mg/kg), PC-5 (0.27 ± 0.01 mg/kg), PET-2 (0.12 ± 0.01 mg/kg), and PET-1 (0.09 ± 0.01 mg/kg), respectively. The concentration of heavy metals migrated from the containers is likely to induce a health risk due to bioaccumulation from long-term ingestion of food packaged in them. The findings of this study added knowledge about harmful heavy metals leached from the FCMs in Bangladesh.

Sediment-bound hazardous trace metals(oid) in south-eastern drainage system of Bangladesh: First assessment on human health.

Despite the beneficial aspect of a natural drainage system, increasing human-induced activities, which include urbanization and growth in industrialization, degrade the ecosystem in terms of trace metal contamination. In response, given the great importance of the south-eastern drainage system in Bangladesh, a detailed evaluation of the human health risk as well as the potential ecological risk of trace metals (Be, Cd, Co, Cr, Cu, Hg, Ni, Pb, Se, V, Zn, and As) in Karnaphuli riverbed sediment was conducted. Mean levels of the elements in mg/kg were As (5.62 ± 1.47); Se (0.84 ± 0.61); Hg (0.37 ± 0.23); Be (1.17 ± 0.49); Pb (15.62 ± 8.42); Cd (0.24 ± 0.33); Co (11.59 ± 4.49); Cr (112.75 ± 40.09); Cu (192.67 ± 49.71); V (27.49 ± 10.95); Zn (366.83 ± 62.82); Ni (75.83 ± 25.87). Pollution indicators, specifically contamination factor (CF), pollution load index (PLI), degree of contamination (Cd), enrichment factor (EF), geo-accumulation index (Igeo), and potential ecological risk index (RI), were computed to assess sediment quality. For the first observation of health risk, chronic daily intake (CDI), hazard quotient (HQ), hazard index (HI), carcinogenic risk (CR) and total carcinogenic risk (TCR) indices were calculated. According to the results, CDI values through the ingestion route of both the adult and child groups were organized in the following descending mode respectively: Zn > Cu > Cr > Ni > V > Pb > Co > As > Se > Be > Cd > Hg. The non-carcinogenic risks were generally low for all routes of exposure, except HQingestion was slightly higher for both adults and children. The calculated hazard index (HI) was, nevertheless, within the permitted range (HI < 1). Similarly, none of the metals exhibited any carcinogenic risks, as all CR values were within the 10-4-10-6 range. The need for authoritative efforts and water policy for the sake of the surrounding ecosystem and human health in the vicinity of the examined watershed is strongly felt as an outcome of this study. The purpose of this study is to protect public health by identifying trace metal sources and reducing industrial and domestic discharge into this natural drainage system.

Psidium guajava leaf extract mediated green synthesis of silver nanoparticles and its application in antibacterial coatings.

In this study, Psidium guajava (P. guajava) leaf extract-assisted silver nanoparticles (AgNPs) were synthesized and their antibacterial activities were investigated. The synthesized green AgNPs were characterized by various analytical techniques including UV-Vis spectroscopy, Fourier transform infrared spectroscopy (FTIR), X-ray diffractometry (XRD), field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray (EDX) spectroscopy, etc. From the UV-Vis spectroscopic analysis, the formation of nanoparticles has been confirmed by the color change from light yellow to reddish brown of the solution due to the excitation of the surface plasmon resonance peak at 430 nm. In addition, the FTIR study showed the reduction of Ag ions owing to the presence of biomolecules in the leaf extract, which acted as reducing as well as capping agents. Furthermore, XRD analysis reveals the identified 2θ peaks of AgNPs at ∼39° with cubic structure. The FE-SEM micrograph illustrated the material was formed in nano-dimensions, with an average particle size of ∼12 nm and almost spherical in shape. Moreover, P. guajava-mediated AgNPs demonstrated good antibacterial activity against both Gram-positive (S. aureus) and Gram-negative (E. coli) bacterial strains. The synthesis was performed by a bio-reduction process where a bioactive agent is responsible for reducing metallic ions to metallic nanoparticles as an eco-friendly, cost-effective, non-toxic, one-step, and sustainable method. Therefore, this study may create an imperative synthetic route for the fabrication of green-AgNPs and their application in antibacterial coatings in cotton textiles.

Development and validation of a modified QuEChERS method coupled with LC-MS/MS for simultaneous determination of difenoconazole, dimethoate, pymetrozine, and chlorantraniliprole in brinjal collected from fields and markets places to assess human health risk.

An effective and sensitive analytical method was developed to quantify the most common pesticide residues (difenoconazole, dimethoate, pymetrozine, and chlorantraniliprole) used for brinjal cultivation in Bangladesh. The quantification of the analytes was done using liquid chromatography-tandem mass spectrometry (LC-MS/MS). The samples were extracted using a modified QuEChERS method and followed by purification with dispersive solid phase extraction (d-SPE) sorbents (PSA, GCB, and C18). Matrix-matched calibration with a regression coefficient R2 ≥ 0.9964 were used to minimize the brinjal matrix effect. The method was validated in quintuple (n = 5) at five different spiked levels (8-400 µg/kg) having recoveries in the range of 70.3-113.2% with relative standard deviations RSDs ≤6.8%, limits of detection (LOD) and limits of quantification (LOQ) was in the range of 0.15-0.66 µg/kg and 0.4-2.0 µg/kg, respectively, for the four analytes. A total 100 samples (50 samples directly from fields of Jessore district, Bangladesh and 50 samples from local market of Dhaka, Bangladesh) were collected to analyse the pesticides residue. The result showed that pesticides residue was found in both the field and market collected samples, 54% and 38%, respectively. The overall mean residue levels of four pesticides in field samples were significantly higher than those of market samples. Moreover, 20% of the field samples and 10% of the market samples had dimethoate residues, which were the most abundant among the four analytes and it ranged from 0.017 to 0.252 mg/kg. In terms of health risk assessments, dimethoate showed the highest estimated daily intake (EDI) and hazard quotient (HQ) values that are 3.02 × 10-5 mg/kg/day and 1.51%, respectively, in field samples. Till now, there have been no regulations or guidelines for the maximum admissible pesticide residue in Bangladesh. Therefore, the above findings will be an initial step for the regulatory authorities of Bangladesh to implement regulations and guidelines for pesticide usage.

A Fast Adsorption of Azithromycin on Waste-Product-Derived Graphene Oxide Induced by H-Bonding and Electrostatic Interactions.

Graphene oxide (GO) was prepared from the graphite electrode of waste dry cells, and the application of the prepared GO as a potential adsorbent for rapid and effective removal of an antibiotic, azithromycin (AZM), has been investigated. The synthesis process of GO is very simple, cost-effective, and eco-friendly. As-prepared GO is characterized by field-emission scanning electron microscopy, energy-dispersive X-ray, transmission electron microscopy, X-ray diffractometry, Fourier transform infrared spectroscopy, elemental analysis, Brunauer-Emmett-Teller sorptometry, and zeta potential analysis. The obtained GO has been employed for removal of the widely used AZM antibiotic from an aqueous solution. The quantitative analysis of AZM before and after adsorption has been carried out by liquid chromatography tandem mass spectrometry. The adsorption of AZM by GO was performed in a batch of experiments where the effects of adsorbent (GO) dose, solution pH, temperature, and contact time were investigated. Under optimum conditions (pH = 7.0, contact time = 15 min, and adsorbent dose = 0.25 g/L), 98.8% AZM was removed from the aqueous solution. The rapid and effective removal of AZM was significantly controlled by the electrostatic attractions and hydrogen bonding on the surface of GO. Adsorption isotherms of AZM onto GO were fitted well with the Freundlich isotherm model, while the kinetic data were fitted perfectly with the pseudo-second order. Therefore, the simple, cost-effective, and eco-friendly synthesis of GO from waste material could be applicable to fabricate an effective and promising low-cost adsorbent for removal of AZM from aqueous media.

Effects of yttrium doping on structural, electrical and optical properties of barium titanate ceramics.

In this report, we study the Yttrium-doped Barium Titanate (Y-BT) Ba1 - xYxTiO3 (with x = 0.00, 0.01, 0.03, 0.05, 0.07 mmol) perovskite ceramics synthesized by sol-gel method. The as-made powder samples were pressed into a pellet shape and subsequently sintered at 1300 °C for 5 h in air. The structural, morphological, electrical, and optical properties of the synthesized samples were investigated by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), impedance analyzer, and UV-Vis-NIR Spectroscopy respectively. The XRD study revealed the formations of single phase tetragonal structure of Barium Titanate (BT) with ∼23-33 nm mean crystallite size. The crystallite size increases initially with Y-doping, found at about 33 nm for x = 0.01, and reduces for increase in Y3+ concentration further. The microstructural study from FESEM depicts the uniform distribution of compact and well-faceted grain growth for Y-BT in contrast with undoped barium titanate. The average grain size (∼0.29-0.78 µm) of the Y-BT decreases with increasing doping concentration. Frequency-dependent impedance analyses show enhanced dielectric properties like dielectric constant, quality factor, and conductivity with low dielectric loss in the presence of Yttrium. The optical bandgap energy (∼2.63-3.72 eV) estimated from UV-Vis-NIR diffuse reflection data shows an increasing trend with a higher concentration of yttrium doping.