boron and hydroxide-ion

Polyethylene (PE) is one the most used plastics worldwide for a wide range of applications due to its good mechanical and chemical resistance, low density, cost efficiency, ease of processability, non-reactivity, low toxicity, good electric insulation, and good functionality. However, its high flammability and rapid flame spread pose dangers for certain applications. Therefore, different flame-retardant (FR) additives are incorporated into PE to increase its flame retardancy. In this review article, research papers from the past 10 years on the flame retardancy of PE systems are comprehensively reviewed and classified based on the additive sources. The FR additives are classified in well-known FR families, including phosphorous, melamine, nitrogen, inorganic hydroxides, boron, and silicon. The mechanism of fire retardance in each family is pinpointed. In addition to the efficiency of each FR in increasing the flame retardancy, its impact on the mechanical properties of the PE system is also discussed. Most of the FRs can decrease the heat release rate (HRR) of the PE products and simultaneously maintains the mechanical properties in appropriate ratios. Based on the literature, inorganic hydroxide seems to be used more in PE systems compared to other families. Finally, the role of nanotechnology for more efficient FR-PE systems is discussed and recommendations are given on implementing strategies that could help incorporate flame retardancy in the circular economy model.

Topics: Boron; Flame Retardants; Hot Temperature; Hydroxides; Inorganic Chemicals; Microscopy, Electron, Scanning; Nanocomposites; Nanotechnology; Nitrogen; Oxygen; Phosphorus; Polyethylene; Polymers; Silicon; Triazines

Topics: Boron; Calcium; Europium; Hydroxides; Luminescence; Oxygen; Phosphorus

The aim of the study was to demonstrate the application potential of boron-doped diamond electrodes (BDD) in electrochemical disinfection of biologically treated sewage for direct recycling of domestic wastewater. Discontinuous bulk disinfection experiments with secondary effluents and model solutions were performed to investigate the influence of operating conditions and wastewater parameters on disinfection efficiency and formation of disinfection by-products (adsorbable organically bound halogens, AOX). The inactivation rate accelerates with increasing current density caused by a faster generation of electrochemical oxidants (ECO). It could be shown that the effect of OH radicals in case of the direct electrochemical disinfection of chloride-containing secondary effluents with BDD is negligible because of their fast reaction with typical radical scavengers. The dominating role of electrochemically generated free chlorine in the disinfection process could be explicitly verified. It could be also shown that the disinfection efficiency is strongly affected by the specific wastewater parameters temperature and pH. These effects can be explained by the behaviour of the reactive species. The migration-controlled generation of ECO can be accelerated under turbulent hydrodynamic conditions. The formation of disinfection by-products (AOX) correlates with the introduced electric charge Q applied per volume and is independent of the applied current density.

Topics: Biodegradation, Environmental; Boron; Chlorine; Conservation of Natural Resources; Diamond; Disinfection; Electrochemical Techniques; Electrodes; Hydrogen-Ion Concentration; Hydroxides; Kinetics; Sewage; Temperature; Waste Disposal, Fluid; Water Pollutants