Activated spent tea (AST) was prepared and characterized by using different techniques such as BET, FTIR and SEM. It is used for methylene blue (MB) dye removal from aqueous solution in a batch system. Experimental results showed that natural basic pH, increased initial dye concentration, and high temperature favored the adsorption. Analysis based on the artificial neural network (ANN) indicated that the adsorbent dose and time with the relative importance of 30.03 and 35.44%, respectively, appeared to be the most influential parameters in the MB adsorption. The adsorption of MB was relatively fast and the Avrami fractional order and pseudo-second-order kinetic models showed satisfactory fit with the experimental data. The equilibrium data were well fitted by the Langmuir and Liu isotherm models, with a maximum sorption capacity of 104.2 mg/g. Also, the obtained values of thermodynamic parameters showed that the adsorption of MB onto AST is endothermic and spontaneous. The results of this study indicated that AST was a reliable adsorbent for removing cationic dyes from wastewater.

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Background Few studies have examined nano-sized plastic particulates (NPs) exposure in relation to oxidative stress and biochemical responses in rodents, commonly used for toxicity evaluations on which to base risk assessment for humans.Methods Here we explored possible oxidative stress and biochemical responses of five weeks oral exposure to polystyrene (PS) nanoparticles (1, 3, 6 and 10 mg/kg body weight per day) in male rats. We used variance analysis and variance explained statistic eta-squared (𝜂2) to estimate the strength of relationships worked out. The whole body scanning further provided insight into the bio-distribution of nanoplastics upon oral exposure.Results Results demonstrated the accumulation of PS-NPs through whole body and also a dose-dependent increase in the production of reactive oxygen species (ROS). Significant alterations in antioxidant responses including serum levels of catalase, superoxide dismutase (SOD), and total glutathione content were noticed, pointing towards a perturbation of redox state induced by the exposure conditions. Acetylcholinesterase level in highest dose group was about 40 percent lower than those in control group. Biochemical parameters viz. glucose, cortisol, lipase, lactate, lactate dehydrogenase (LDH), alkaline phosphatase, gamma-glutamyl transpeptidase (GGT), triglycerides, and urea showed a significant increase, while total protein, albumin and globulin levels showed an appreciable decline.Conclusion The pattern of associations noticed with AChE activity and biochemical responses in our study suggests the possibility that a neurobehavioral effect or dysfunctions in energy metabolism, or both, may be the potential mode of action, possibly through stress response as well as liver function. Perturbations of creatinine and uric acid levels are indeed plausible biological explanations for the association with kidney dysfunction. Although we provided a new scientific clue for exploring the biological effects of plastics nanoparticles, the results warrant additional research with a larger sample size. The suggested potential mechanisms also remains to be investigated.