Adsorption of reactive black 5 (RB5) from aqueous solution onto chitosan was investigated in a batch system. The effects of solution pH, initial dye concentration, and temperature were studied. Adsorption data obtained from different batch experiments were modeled using both pseudo first-and second-order kinetic equations. The equilibrium adsorption data were fitted to the Freundlich, Tempkin, and Langmuir isotherms over a dye concentration range of 45-100 mmol/L. The best results were achieved with the pseudo second-order kinetic and Langmuir isotherm equilibrium models, respectively. The equilibrium adsorption capacity (q e ) was increased with increasing the initial dye concentration and solution temperature, and decreasing solution pH. The chitosan flakes for the adsorption of the dye was regenerated efficiently through the alkaline solution and was then reused for dye removal. The activation energy (E a ) of sorption kinetics was estimated to be 13.88 kJ/mol. Thermodynamic parameters such as changes in free energy (DG), enthalpy (DH), and entropy (DS) were evaluated by applying the van't Hoff equation. The thermodynamics of reactive dye adsorption by chitosan indicates its spontaneous and endothermic nature.

The aim of the present study was to evaluate the protective effect of Syzygium cymosum leaf methanol extract (SCL) against carbofuran (CF)induced hepatotoxicity in Sprague−Dawley rats, along with the identification and quantification of polyphenolic composition by high-performance liquid chromatography (HPLC). Results revealed the presence of alkaloids, tannins, and flavonoids in SCL. Similarly, HPLC analysis suggests that SCL contains some known important antioxidants, such as rutin, benzoic acid, and salicylic acid that could be responsible for the hepatoprotective activity of the extract. In CFexposed rats, significant hematological alterations along with histological changes were marked by the presence of necrosis, congestion, and inflammation. CFintoxication also showed an increase in lipid peroxidation and decrease in cellular antioxidant enzymes (e.g., superoxide dismutase, catalase, and glutathione peroxidase) levels in rats compared with the control group. Furthermore, coadministration of SCL significantly ameliorated the abnormalities and improved the cellular arrangement in experimental animals. SCL also reversed the alteration of hematological and biochemical parameters and brought them back to normal levels as compared to the control group. In conclusion, S. cymosum may be one of the best sources of natural antioxidant compounds that can be used in the treatment of oxidative stress and stress-related diseases and disorders.

Heavy metal pollution in groundwater is a substantial environmental risk for Bangladesh. The Meghna Ghat industrial area in Bangladesh becomes a promising site for installing various industries for few decades. It was necessary to assess the heavy metal level in the groundwater of this area, and current study took the initiative. We collected 20 groundwater samples and tested pH, DO, TDS, EC, turbidity, COD, and DOC as well as four heavy metals (Cr, Cd, Pb, and Ni) to calculate four water quality indices, i.e., water quality index (WQI), degree of contamination (DC), heavy metal evaluation index (HEI), and heavy metal pollution index (HPI). Ni was too low to detect by the instrument, whereas the mean concentrations of Cr, Cd, and Pb were 0.07, 0.007, and 0.18 mg/L which exceeded the drinking water standards set by Bangladesh. According to the water quality indices, only 10% samples were good according to WQI; 30% and 15% samples were subjected to low level of pollution considering DC and HEI, respectively. Although according to HPI 35% samples were unsuitable for drinking, rest of the values were very close to characterize as unsuitable. Finally, we proposed two best-fitted models that can represent relationships between the metals and water quality indices. Water quality was comparatively better near the open spaces of the study area. The area needed to be under continuous monitoring for checking further pollution distribution.

Sundarban honey is one of the most renowned and popular types of honey from Bangladesh. This study was undertaken to investigate the antioxidant and DNA damage inhibition potentials of Sundarban honey. The estimated polyphenol, flavonoid, ascorbic acid, reducing sugar and protein contents in the investigated honey were found to be 593.96 ± 13.71 mg GAEs/kg, 50.00 ± 0.00 mg CEs/kg, 117.04 ± 1.05 mg/kg, 60.58 ± 3.23 g/100 g and 6.43 ± 0.12 mg/g, respectively. Some phenolics including gallic acid, pyrogallol, vanillic acid and trans‐Cinnamic acid, as well as three flavonoids, naringin, rutin and quercetin, were identified and quantified by high performance liquid chromatography. Sundarban honey was found to possess protective activity against hydrogen peroxide and UV irradiation‐induced damage to pBR322. The DNA protection activity of honey corresponded to its antioxidant potential and exhibited dose‐dependent effects. Practical Application Sundarban honey, a wild multifloral honey produced by Apis dorsata bees is one of the most renowned types of honey from Bangladesh and confers protection against oxidative stress‐induced liver and kidney damage. This honey can a be very good source of natural antioxidant which particularly contains some phenolic compounds including gallic, vanillic and trans‐Cinnamic acids as well as three flavonoids (naringin, rutin and quercetin). Sundarban honey can protect against oxidative DNA damage and consecutive illness.

Chitosan was utilized as adsorbent to remove methyl orange (MO) from aqueous solution by adsorption. Batch experiments were conducted to study the effects of pH, initial concentration of adsorbate and temperature on dye adsorption. The kinetic data obtained from different batch experiments were analyzed using both pseudo first-order and pseudo second-order equations. The equilibrium adsorption data were analyzed by using the Freundlich and Langmuir models. The best results were achieved with the pseudo second-order kinetic model and with the Langmuir isotherm equilibrium model. The equilibrium adsorption capacity (qe) increases with increasing the initial concentration of dye and with decreasing pH. The values of qe were found to be slightly increased with increasing solution temperatures. The activation energy (Ea) of sorption kinetics was found to be 10.41 kJ/mol. Thermodynamic parameters such as change in free energy (△G), enthalpy (△H) and entropy (△S) were also discussed