A new activated adsorbent was produced from the debris of Posidonia oceanica rhizomes (POR). POR were activated in acetic acid and utilized as an eco-adsorbent for the removal of cationic dye methylene blue (MB) from saline solutions. The purified Posidonia oceanica rhizomes (PPOR) and its activated form (APOR) were characterized by elemental analysis, pH-metric titration, Fourier transformer infrared (FTIR), and surface area measurements, which inferred a remarkable activation of APOR. An enhancement in the free acidic sites was confirmed. The adsorption data obtained were analyzed using Langmuir, Freundlich, Temkin, Dubinin-Kaganer-Raduskavich (DKR), and Redlich and Peterson (RP) isotherm models. The obtained data from these isotherm models were tested using some error functions (residual root mean squares error (RMSE), sum square error (SSE), and chi-square test (X²) function). Temkin isotherm model was the best isotherm fits the experimental data of APOR. Kinetic data were evaluated by pseudo-first-order (PFO), pseudo-second-order (PSO), and intraparticle diffusion models. The adsorption rate was found to follow PSO model with a good correlation (R² = 0.999–1). A suggested, endothermic, multilayer, combined electrostatic and physical adsorption mechanism may be responsible for the removal of MB from water utilizing APOR. Adsorption is anticipated to start with chemisorption on active functional groups of adsorbent’s surface followed by physisorption of the subsequent layers through adsorbate–adsorbate interaction. The removal process was successfully applied for MB-spiked saline and brackish water with removal efficiencies of 51.7–97.2%. The results revealed that activated Posidonia oceanica rhizomes is a promising adsorbent for the removal of the methylene blue dye from real saline and brackish water with high removal efficiencies. Graphical Abstract

Microbial degradation is an important process for removing many organic chemicals from natural waters. The estimation of biodegradability of chemicals which reach the aquatic environment is necessary in assessing the hazard associated with their use. Phenol has many industrial applications and it finds its way into wastewater streams. It is toxic to several biochemical reactions. However, biological transformation of phenol to non-toxic entities is possible. In this article, the data of biodegradation of phenol at different concentrations were studied. For phenol concentrations equal to or less than 147 mg/L, the plateau (the stage associated with the termination of carbon) BOD (biochemical oxygen demand) was calculated to be 169.47% of the corresponding initial phenol concentration, the BOD of the biomass produced up to the plateau was calculated to be 70% of the corresponding initial phenol concentration. This study shows that the biomass produced up to the plateau, the plateau BOD, and the ultimate BOD can all be estimated for phenol concentrations less than 147 mg/L just if the initial phenol concentration is known and without having to repeat the time-consuming BOD experiments.

The current situation in many developing countries is that, vegetable oils are replacing animal fats because of health concerns and cost. The objective of the study was to compare the iodine value, acid value, ester value, peroxide value, saponification number and cholesterol content of some locally produced vegetable oils like refined marula cooking oil, marula traditional cooking oil, marula cosmetic oil, melon oil, ximenia oil viz. olive oil and commercial sunflower oil. The physicochemical analysis helps to justify the usage of these different traditional oils. The analysis showed that marula cooking oil is close to olive oil in the unsaturation level and better than olive oil in ester value, peroxide value and has lower cholesterol content. Key words: Marula cooking oil, marula traditional oil, marula cosmetic oil, melon oil, olive oil, ximenia oil and sunflower oil.