Selenium (Se) recovery for technological applications from environmental matrices based on biotic and abiotic mechanisms.

Selenium (Se) is an essential element with application in manufacturing from food to medical industries. Water contamination by Se is of concern due to anthropogenic activities. Recently, Se remediation has received increasing attention. Hence, different types of remediation techniques are listed in this work, and their potential for Se recovery is evaluated. Sorption, co-precipitation, coagulation and precipitation are effective for low-cost Se removal. In photocatalytic, zero-valent iron and electrochemical systems, the above mechanisms occur with reduction as an immobilization and detoxification process. In combination with magnetic separation, the above techniques are promising for Se recovery. Biological Se oxyanions reduction has been widely recognized as a cost-effective method for Se remediation, simultaneously generating biosynthetic Se nanoparticles (BioSeNPs). Increasing the extracellular production of BioSeNPs and controlling their morphology will benefit its recovery. However, the mechanism of the microbial production of BioSeNPs is not well understood. Se containing products from both microbial reduction and abiotic methods need to be refined to obtain pure Se. Eco-friendly and cost-effective Se refinery methods need to be developed. Overall, this review offers insight into the necessity of shifting attention from Se remediation to Se recovery.

Role of H2O2 in the fluctuating patterns of COD (chemical oxygen demand) during the treatment of palm oil mill effluent (POME) using pilot scale triple frequency ultrasound cavitation reactor.

Palm oil mill effluent (POME) is a highly contaminating wastewater due to its high chemical oxygen demand (COD) and biochemical oxygen demand (BOD). Conventional treatment methods require longer residence time (10-15 days) and higher operating cost. Owing to this, finding a suitable and efficient method for the treatment of POME is crucial. In this investigation, ultrasound cavitation technology has been used as an alternative technique to treat POME. Cavitation is the phenomenon of formation, growth and collapse of bubbles in a liquid. The end process of collapse leads to intense conditions of temperature and pressure and shock waves which assist various physical and chemical transformations. Two different ultrasound systems i.e. ultrasonic bath (37 kHz) and a hexagonal triple frequency ultrasonic reactor (28, 40 and 70 kHz) of 15 L have been used. The results showed a fluctuating COD pattern (in between 45,000 and 60,000 mg/L) while using ultrasound bath alone, whereas a non-fluctuating COD pattern with a final COD of 27,000 mg/L was achieved when hydrogen peroxide was introduced. Similarly for the triple frequency ultrasound reactor, coupling all the three frequencies resulted into a final COD of 41,300 mg/L compared to any other individual or combination of two frequencies. With the possibility of larger and continuous ultrasonic cavitational reactors, it is believed that this could be a promising and a fruitful green process engineering technique for the treatment of POME.

The impact of impurities in various crude A. annua extracts on the analysis of artemisinin by liquid chromatographic methods.

Analysis of Artemisia annua extracts by liquid chromatographic methods has traditionally been complicated by the presence of significant quantities of impurities. It has been observed that these impurities often remain as a solid residue after sample reconstitution, but the possibility of artemisinin remaining entrained within this waxy layer has not been detailed in the literature. This investigation found that A. annua extract impurities have a critical impact on the quantification of artemisinin by liquid chromatographic methods. Extended sample reconstitution times of up to 24h are required in order for the mobile phase (acetonitrile) to penetrate the residue and solubilise the artemisinin contained within. Extracts produced using ethyl acetate, hexane-ethyl acetate (95:5, v/v), hexane and ethanol were examined in the study. Extended residue reconstitution times resulted in a significant increase in the number and concentration of impurities in the mobile phase, requiring the development of a new HPLC-UV analytical method to exact adequate separation of artemisinin for quantification. The solvent selectivity and capacity for each of the solvent extraction approaches was then determined using the new reconstitution and HPLC-UV methods.