Search Results (3)

Membrane contactors have proved to be effective for recovering ammonia from wastewater by absorbing it into a trapping solution. This study compares the performance of sulfuric acid and citric acid as trapping solutions in a pilot-scale plant for recovering ammonia from sludge digestion liquors using membrane contactors in a liquid–liquid configuration operating at pH 10 and a temperature of 37 °C and using ultrafiltration (UF) technology as pretreatment. The performance of the process using sulfuric acid at a lower pH (9.5) and temperature (30 °C) was also studied, as well as the advantage of including a CO₂-stripping module in the process. The ammonia elimination efficiency was 88% and 86% when using sulfuric acid and citric acid, respectively. The nitrogen concentration of the produced ammonium sulfate and ammonium citrate reached 23.2 and 14.7 g NH₃-N·L⁻¹, respectively. The ammonia elimination efficiency when using sulfuric acid decreased to 49% when decreasing the pH to 9.5 and to 85% when decreasing the temperature to 31 °C. UF technology was able to reduce the concentration of suspended solids by 90% and the chemical oxygen demand by 37%. However, the UF membranes for the pretreatment and the membrane contactors for ammonia recovery had to be constantly cleaned with acid due to scaling, which significantly increased maintenance efforts. The CO₂-stripping module reduced the consumption of the caustic soda solution by 23% for increasing the pH level of the treated water. Finally, the specific energy consumption of the plant was 8 kWh·m⁻³. Full article

Membrane contactors are among the available technologies that allow a reduction in the amount of ammoniacal nitrogen released into the environment through a process called transmembrane chemical absorption (TMCA). This process can be operated with different substances acting as trapping solutions; however, strong inorganic acids have been studied the most. The purpose of this study was to demonstrate, at laboratory scale, the performance of citric acid as a capturing solution in TMCA processes for recovering ammonia as an organic fertilizer from anaerobic digestor reject water using membrane contactors in a liquid–liquid configuration and to compare it with the most studied solution, sulfuric acid. The experiments were carried out at 22 °C and 40 °C and with a feed water pH of 10 and 10.5. When the system was operated at pH 10, the rates of recovered ammonia from the feed solution obtained with citric acid were 10.7–16.5 percentage points (pp) lower compared to sulfuric acid, and at pH 10.5, the difference decreased to 5–10 pp. Under all tested conditions, the water vapor transport in the system was lower when using citric acid as the trapping solution, and at pH 10 and 40 °C, it was 5.7 times lower. When estimating the operational costs for scaling up the system, citric acid appears to be a better option than sulfuric acid as a trapping solution, but in both cases, the process was not profitable under the studied conditions. Full article

Chitin and its derivatives are attracting great interest in cosmetic and cosmeceutical fields, thanks to their antioxidant and antimicrobial properties, as well as their biocompatibility and biodegradability. The classical source of chitin, crustacean waste, is no longer sustainable and fungi, a possible alternative, have not been exploited at an industrial scale yet. On the contrary, the breeding of bioconverting insects, especially of the Diptera Hermetia illucens, is becoming increasingly popular worldwide. Therefore, their exoskeletons, consisting of chitin as a major component, represent a waste stream of facilities that could be exploited for many applications. Insect chitin, indeed, suggests its application in the same fields as the crustacean biopolymer, because of its comparable commercial characteristics. This review reports several cosmetic and cosmeceutical applications based on chitin and its derivatives. In this context, chitin nanofibers and nanofibrils, produced from crustacean waste, have proved to be excellent cosmeceutical active compounds and carriers of active ingredients in personal care. Consequently, the insect-based chitin, its derivatives and their complexes with hyaluronic acid and lignin, as well as with other chitin-derived compounds, may be considered a new appropriate potential polymer to be used in cosmetic and cosmeceutical fields. Full article