Ionic liquids removal by sequential photocatalytic and biological oxidation

Abstract

BACKGROUND The industrial application of ionic liquids (ILs) can induce the generation of wastewater and their release into the aquatic media. ILs can be efficiently removed by advanced oxidation processes (AOPs), which are expensive to implement. An alternative, using solar photocatalysis and biological degradation in combination, was used here to remove 1‐hexyl‐3‐methylimidazolium chloride (HmimCl) and 1‐butyl‐4‐methylpyridinium chloride (BmpyrCl). The chemical pretreatment allowed the ILs to be converted into by‐products for easier biodegradation in a sequential batch reactor (SBR). RESULTS Photocatalytic degradation, using 0.25 g TiO2 L−1 and 600 W m−2 solar radiation for 24 h, allowed a complete ILs removal and a partial mineralization of the organic matter, 28% for Bmpyr+ and 35% for Hmim+. A degradation pathway based on the by‐products identified was proposed for each IL. The reaction effluents were submitted to a biological treatment in an SBR, using organic loading rates of 0.18–0.2 kg COD kg−1 VSS d−1 and a biomass concentration of 3.5 g VSS L−1 in 8 h cycles. The combined treatment allowed highly efficient removal of organic matter [total organic carbon (TOC) conversion exceeded 75% for HmimCl and 78% for BmpyrCl]. CONCLUSION Solar photocatalytic oxidation efficiently removed ILs and produced more biodegradable and less ecotoxic effluents. Biological oxidation increased TOC and chemical oxygen demand (COD) removal to more than 75% for the overall treatment. Combining solar photocatalysis and biological degradation therefore provided an effective system for IL removal. © 2019 Society of Chemical Industry

Comprehensive Kinetics of the Photocatalytic Degradation of Emerging Pollutants in a LED-Assisted Photoreactor. S-Metolachlor as Case Study

“…Degradation of MTLC by conventional treatments such as physical adsorption [7], coagulation, chlorination or biological [8] and bio-electrochemical [9] treatments has been studied, but these technologies report a low yield. Therefore, high-performance and low-cost processes such as Advanced Oxidation Processes (AOPs) are sought for the efficient degradation of this pesticide [3,[10][11][12][13][14][15][16].…”

“…Among AOPs, heterogeneous photocatalysis is effective for the removal of many recalcitrant organic contaminants from polluted waters [3,[10][11][12][13][14][15][16]. One of its main advantages is that solar light can activate the catalyst.…”

“…However, some challenges remain unsolved to improve the overall photocatalytic process efficiency. Recently, the use of ultraviolet Light-Emitting Diodes (LEDs) as a light source in photocatalytic processes has received increasing attention due to their high efficiency and stability [13,14,17,18]. Thus, modeling the radiation field and the spatial distribution of the radiation absorption inside LEDassisted photocatalytic reactors is a scientific challenge that can contribute to the further development of the technology [19][20][21][22][23].…”

“…Regarding the degradation kinetics, most previous photocatalytic studies proposed pseudo-first-order kinetic equations to describe the degradation rate of the target species, thus the influence of radiation absorption by the catalyst was lumped in the kinetic constant. Therefore, developing a kinetics expression that disaggregates the reaction kinetics parameters from the radiation parameters becomes necessary to advance the reactor design [12][13][14]16,[32][33][34][35].…”

In Focus: ANQUE‐ICCE‐CIBIQ 2019

“…In addition, the reclamation of transition metals, namely, nickel and copper, is sought from industrial spent sulfuric acid solutions using chelating resins . Regarding water supply and the treatment of aqueous effluents, the surface modification of microfiltration membranes is proposed to enhance their anti‐fouling properties for seawater desalination, and a combined photo‐catalytic process with a biological treatment is applied to the degradation of ionic liquids in aqueous media …”