Phosphate adsorption improvement using a novel adsorbent by CaFe/LDH supported onto CO2 activated biochar.

It is imperative to remove phosphate from the aquatic system. This nutrient in excess can cause environmental problems such as eutrophication. Therefore, aiming to enhance phosphate removal, this work presents a novel adsorbent developed from the construction of Ca2+/Fe3+ layer double hydroxides (CaFe/LDH) supported onto biochar physically activated with CO2 [CaFe/biochar (CO2)]. Pristine biochar was produced from the pyrolysis of Eucalyptus saligna sawdust, activated with CO2, and then impregnated with CaFe/LDH. The CaFe/biochar (CO2) was characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and Brunauer-Emmett-Teller (BET). The characterization confirmed a proper synthesis of the new adsorbent. Experiments were conducted in the form of batch adsorption. Results indicated that the optimum pH and adsorbent dosage were 2.15 and 0.92 g L-1, respectively. Adsorption kinetics, isotherms, and thermodynamics were also evaluated. Adsorption kinetics and isotherms were better fitted by the pseudo n order and Freundlich models, respectively. Results also indicated a better adsorption capacity (99.55 mg·g-1) at 55 °C. The thermodynamic indicators depicted that the adsorption process was favorable, spontaneous, and endothermic. Overall, CaFe/biochar (CO2) could be potentially applied for the adsorptive removal of phosphate from an aqueous solution.

Membrane Distillation: Pre-Treatment Effects on Fouling Dynamics.

In the research reported in this paper, membrane distillation was employed to recover water from a concentrated saline petrochemical effluent. According to the results, the use of membrane distillation is technically feasible when pre-treatments are employed to mitigate fouling. A mathematical model was used to evaluate the fouling mechanism, showing that the deposition of particulate and precipitated material occurred in all tests; however, the fouling dynamic depends on the pre-treatment employed (filtration, or filtration associated with a pH adjustment). The deposit layer formed by particles is not cohesive, allowing its entrainment to the bulk flow. The precipitate fouling showed a minimal tendency to entrainment. Also, precipitate fouling served as a coupling agent among adjacent particles, increasing the fouling layer cohesion.

Genotoxic potential and physicochemical parameters of Sinos River, southern Brazil.

The present study aimed to evaluate the physicochemical parameters and the genotoxic potential of water samples collected in the upper, middle, and lower courses of the Sinos River, southern Brazil. The comet assay was performed in the peripheral blood of fish Hyphessobrycon luetkenii exposed under laboratory conditions to water samples collected in summer and winter in three sampling sites of Sinos River. Water quality analysis demonstrated values above those described in Brazilian legislation in Parobé and Sapucaia do Sul sites, located in the middle and in the lower courses of the Sinos River, respectively. The Caraá site, located in the upper river reach, presented all the physicochemical parameters in accordance with the allowed limits in both sampling periods. Comet assay in fish revealed genotoxicity in water samples collected in the middle course site in summer and in the three sites in winter when compared to control group. Thus, the physicochemical parameters indicated that the water quality of the upper course complies with the limits set by the national guidelines, and the ecotoxicological assessment, however, indicated the presence of genotoxic agents. The present study highlights the importance of combining water physicochemical analysis and bioassays to river monitoring.