New low-cost biofilters for SARS-CoV-2 using Hymenachne grumosa as a precursor

The ongoing global spread of COVID-19 (SARS-CoV-2 2019 disease) is causing an unprecedented repercussion on human health and the economy. Despite the primary mode of transmission being through air droplets and contact, the transmission via wastewater is a critical concern. There is a lack of techniques able to provide complete disinfection, along with the uncertainty related to the behavior of SARS-CoV-2 in the natural environment and risks of contamination. This fact makes urgent the research towards new alternatives for virus removal from water and wastewater. Thus, this research aimed to characterize new lost-cost adsorbents for SARS-CoV-2 using Hymenachne grumosa as a precursor and verify its potential for removing SARS-CoV-2 from the solution. The aquatic macrophyte H. grumosa had in natura and activated carbon produced with H. grumosa and zinc chloride (ZnCl_2,1:1) impregnation and carbonization (700 °C, 1 h) were incubated for 24 h with inactivated SARS-CoV-2 viral suspension, and then the ribonucleic acid (RNA) was extracted and viral load quantified through reverse transcription-quantitative polymerase chain reaction (RT-qPCR) technique. The results demonstrated the great adsorption potential, achieving removal of 98.44% by H. grumosa "in natura", and 99.61% by H. grumosa with carbon activation, being similar to commercial activated carbon (99.67%). Thus, this study highlights the possibility of low-cost biofilters to be used for SARS-CoV-2 removal, as an excellent alternative for wastewater treatment or watercourses decontamination.

Chitosan-coated sand and its application in a fixed-bed column to remove dyes in simple, binary, and real systems

Adsorption of tartrazine yellow food dye, in a fixed-bed column, was carried out using a single system, a binary system (in the presence of sunset yellow food dye), and in a real effluent provides from an ice cream industry. Chitosan was used to coat sand particles by the dip-coating technique, and these particles were applied in fixed-bed adsorption. The assays were performed in flow rates of 3 mL min^-1 and 5 mL min^-1. The best performance was reached at 3 mL min^-1. In this flow rate, for single and binary systems, the breakthrough time was 95 min and 65 min, and the maximum capacity of the column was around 595 mg g^-1 and 497 mg g^-1, respectively. In the assay conducted with the real effluent, the breakthrough time was 10 min, and the maximum adsorption capacity of the column was reduced to 191 mg g^-1 for tartrazine dye. The dynamic models of Thomas and Yoon-Nelson were used, and both were suitable to represent the breakthrough curves.

Biosorption of glycerol impurities from biodiesel production onto electrospun chitosan-based nanofibers: equilibrium and thermodynamic evaluations

The increase in biodiesel production has been leading to an excess amount of crude glycerol and, consequently, serious environmental issues. For this reason, electrospun chitosan-based nanofibers (CB-EN), composed by chitosan and poly(ethylene oxide) (PEO), were synthesized to apply in the biosorption of impurities from industrial glycerol. To evaluate the biosorption efficiency, the chitosan-based nanofiber was compared to other chitosan-based biosorbents (chitosan biopolymeric film and chitosan powder). The equilibrium and thermodynamic studies were successfully performed to comprehend the interaction mechanisms through the biosorption of glycerol pigments onto electrospun chitosan-based nanofibers. The temperature effect was evaluated by experimental equilibrium curves. Freundlich and BET models were used to estimate isotherm parameters. Gibbs free energy change, enthalpy change, entropy change, and isosteric heat of biosorption were quantified. The equilibrium curves showed that the highest equilibrium relative adsorption (340.7 g^-1) was reached at 60 °C. The BET model was the most suitable to represent the equilibrium behavior. The thermodynamic parameters indicated that the biosorption was spontaneous, exothermic, random, and energetic heterogeneous. Therefore, this work developed a green and efficient alternative to refine industrial glycerol. Graphical abstract Note: This data is mandatory. Please provide.