Performance modelling of seawater electrolysis in an undivided cell: Effects of current density and seawater salinity

The application of two-phase composite absorbent systems consisting of BAD and seawater resources in the wet treatment of ship exhaust gas

The impact of ship emissions on the environment cannot be ignored and should be controlled. The possibility of applying seawater electrolysis technology and a novel amide absorbent (BAD, C₁₂H₂₅NO) to the simultaneous desulfurization and denitrification of ship exhaust gas is entirely confirmed by using various seawater resources. Concentrated seawater (CSW) with high salinity can effectively reduce the heat generated during electrolysis and the escape of chlorine. The initial pH of the absorbent can greatly affect the NO removal capacity of the system, and the BAD could keep the pH range suitable for NO oxidation in the system for a long time. The use of fresh seawater (FSW) to dilute the electrolysis of concentrated seawater (ECSW) to make an aqueous oxidant is a more reasonable scheme; the average removal efficiencies of SO₂, NO, and NOx were 97.10%, 75.41%, and 74.28%, respectively. The synergistic effect of HCO₃ ^-/CO₃ ^2- and BAD was shown to further restrict NO₂ escape.

Nannochloropsis oceanica harvested using electrocoagulation with alternative electrodes - An innovative approach on potential biomass applications

Electrocoagulation is a promising technology to harvest microalgal biomass. However, the commonly used aluminum electrodes release undesired salts that decrease biomass value. In this study, alternative iron, zinc, and magnesium electrodes and operational parameters pH, time and current density were studied to harvest Nannochloropsis oceanica. For recovery efficiency and concentration factor the initial pH was most important using iron electrodes, while time and current density were more relevant using zinc and magnesium electrodes. Optimal parameters resulted in biomass recovery efficiencies > 95%, biomass was concentrated 2.8-7.2 times and contained 15.7-29.1% ashes. Elemental analysis revealed metal salts in harvested biomass resulting from electrode corrosion. Finally, ash contents could be reduced by 65% using EDTA as a chelating agent. The electrocoagulation harvested microalgal biomass enriched in essential metals may be a promising bioresource for agricultural growth inducers, or functional ingredients for feed.

Comprehensive treatment of marine aquaculture wastewater by a cost-effective flow-through electro-oxidation process

The effective treatment of marine aquaculture wastewater is of great significance to protect marine environment and marine organisms. This study validated the feasibility of the comprehensive removal of NH₄⁺-N, NO₂^--N, COD and P, as well as disinfection and antibiotics removal from marine aquaculture wastewater by electrochemical oxidation (EO), comparing the performance and energy consumption with that by electro-peroxone (EP) and electro-Fenton (EF) process. Due to the formation of more free chlorine, the removal of NH₄⁺-N and COD was in order of EO ≫ EP > EF. A new flow-through EO reactor was adopted, which was found enhanced the formation rate of free chlorine and degradation rate of pollutants, and thus performed better than that of flow-by reactor and batch reactor. By this flow-through EO process, the removal of NH₄⁺-N and NO₂^--N could reach >90% and their concentrations after treatment both meet the Water Drainage Standard for Sea Water Mariculture (SC/T 9103-2007). Meanwhile, the process had a good bactericidal performance with a lg(c/c₀) of -5.6. At the same time, antibiotics such as sulfadimidine (SMT) and norfloxacin (NOR) could be completely removed. The energy consumption was only 0.054 kWh/g NH₄⁺-N (0.27 kWh/m³), which was far more cost-effective than other oxidative processes. The new flow-through EO process has great practical application prospects for the comprehensive removal of multiple pollutants and sterilization from marine aquaculture wastewater.