Exploration of Zero-Valent Iron Stabilized Calcium–Silicate–Alginate Beads’ Catalytic Activity and Stability for Perchlorate Degradation

Removal of low concentration of perchlorate from natural water by quaternized chitosan sphere (CGQS): Efficiency and mechanism research

In this study, an innovative approach utilizing betaine as a raw material was employed to effectively modify the surface of chitosan with quaternary ammonium groups. X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectrometer (FTIR) characterization showed that the quaternary ammonium groups on betaine were successfully loaded on the chitosan surface. The effects of dosage, pH, initial perchlorate concentration, temperature and co-existing anions on the removal efficiency of perchlorate were investigated. The saturated adsorption capacity of CGQS was 35.41 mg/g under natural condition. The impact of initial perchlorate concentrations and column flow rates on the column adsorption experiments were investigated, as well as natural water tests. Sterilizing performance experiments of CGQS were carried out innovatively. Under the condition of initial concentration of 0.5 mg/L, 9 BV/h (bed volume per hour), the effluent natural water was up to standard (≤0.07 mg/L) with a treatment capacity of 210 BV/g, and the sterilizing rate of CGQS was up to 97.02%. The proposed adsorption mechanisms involved surface pore adsorption, electrostatic adsorption of quaternary ammonium groups, and ion exchange between chloride and perchlorate ions. The CGQS prepared in this work had great potential for treating trace perchlorate contamination in natural water.

Silica-Calcium-Alginate Hydrogels for the Co-Immobilization of Glucose Oxidase and Catalase to Reduce the Glucose in Grape Must

Higher temperatures due to climate change are causing greater sugar production in grapes and more alcoholic wines. The use of glucose oxidase (GOX) and catalase (CAT) in grape must is a biotechnological green strategy to produce reduced-alcohol wines. GOX and CAT were effectively co-immobilized by sol-gel entrapment in silica-calcium-alginate hydrogel capsules. The optimal co-immobilization conditions were achieved at a concentration of the colloidal silica, sodium silicate and sodium alginate of 7.38%, 0.49% and 1.51%, respectively, at pH 6.57. The formation of a porous silica-calcium-alginate structure was confirmed by environmental scanning electron microscopy and the elemental analysis of the hydrogel by X-ray spectroscopy. The immobilized GOX showed a Michaelis-Menten kinetic, while the immobilized CAT fits better to an allosteric model. Immobilization also conferred superior GOX activity at low pH and temperature. The capsules showed a good operational stability, as they could be reused for at least 8 cycles. A substantial reduction of 26.3 g/L of glucose was achieved with encapsulated enzymes, which corresponds to a decrease in potential alcoholic strength of must of about 1.5% vol. These results show that co-immobilized GOX and CAT in silica-calcium-alginate hydrogels is a promising strategy to produce reduced-alcohol wines.

Environmental occurrence, toxicity and remediation of perchlorate - A review

Perchlorate (ClO4-) comes under the class of contaminants called the emerging contaminants that will impact environment in the near future. A strong oxidizer by nature, perchlorate has received significant observation due to its occurrence, reactive nature, and persistence in varied environments such as surface water, groundwater, soil, and food. Perchlorate finds its use in number of industrial products ranging from missile fuel, fertilizers, and fireworks. Perchlorate exposure occurs when naturally occurring or manmade perchlorate in water or food is ingested. Perchlorate ingestion affects iodide absorption into the thyroid, thereby causing a decrease in the synthesis of thyroid hormone, a very crucial component needed for metabolism, neural development, and a number of other physiological functions in the body. Perchlorate remediation from ground water and drinking water is carried out through a series of physical-chemical techniques like ion (particle) transfer and reverse osmosis. However, the generation of waste through these processes are difficult to manage, so the need for alternative treatment methods occur. This review talks about the hybrid technologies that are currently researched and gaining momentum in the treatment of emerging contaminants, namely perchlorate.