Absorption is an eminent technology for volatile organic compounds (VOCs) elimination with the merits of high efficiency and low cost. Absorbent plays a critical role in the absorption process, and the thermal stability, saturation capacity, and regeneration performance should be concerned. As a kind of green and eco-friendly solvent, ionic liquid (IL) is expected to be a substitute for the conventional VOCs absorbent. In this study, 1-butyl-3-methylimidazolium hexafluorophosphate ([Bmim][PF₆]) is employed to absorb the modeling VOCs (toluene and acetone). Moreover, the used [Bmim][PF₆] is recovered by thermal distillation and the reusability is then conducted by consecutive batch experiments. Based on that, the thermal stability of [Bmim][PF₆] is comprehensively examined, in which the kinetic and thermodynamic parameters are also calculated. Results reveal that [Bmim][PF₆] owned promising toluene absorption performance with inlet concentration of 3000 mg/m³ and flow rate of 300 mL/min at 20 °C, it possesses the saturated adsorption capacity of 5.16 mg/g. [Bmim][PF₆] also shows satisfying thermal stability up to 610 K. In addition, thermal distillation is proved to be a reliable regeneration route on account of the recovered [Bmim][PF₆] remained satisfying capacity even after five cycles.

Crude oil is a complex mixture of petroleum hydrocarbons (PHC) with distinct chemical, physical and toxicological properties relevant for contaminated site risk assessment. Ecotoxicological effects of crude oil distillation fractions on luminescent bacteria (Vibrio fischeri), earthworms (Dendrobaena hortensis) and invertebrates (Heterocypris incongruens) were tested using two spiked soils and their elutriates. Fraction 2 (F2) had an equivalent carbon number (ECN) range of >10 to 16, and F3 from >16 to 39. F2 showed a substantially higher ecotoxicological effect than F3 for Vibrio and Dendrobaena. In contrast, severe inhibition of Heterocypris by the poorly soluble F3 is attributed to mechanical organ blockage. Immediate sequestration of PHC to the organic matter-rich soil effected reduced toxicity for all organisms. This study indicates that a more differentiated consideration (i) of PHC mixtures based on ECN range and (ii) of model soil properties employed for ecotoxicity testing should be included into PHC-contaminated site risk assessment.

Experimental investigations were carried out on removal of arsenic from contaminated groundwater by employing a new flat-sheet cross flow membrane module fitted with a hydrophobic polyvinylidenefluoride (PVDF) microfiltration membrane. The new design of the solar-driven membrane module in direct contact membrane distillation (DCMD) configuration successfully produced almost 100 per cent arsenic-free water from contaminated groundwater in a largely fouling-free operation while permitting high fluxes under reduced temperature polarization. For a feed flow rate of 0.120 m3/h, the 0.13 μm PVDF membrane yielded a high flux of 74 kg/(m2 h) at a feed water temperature of 40 °C and, 95 kg/m2 h at a feed water temperature of 60 °C. The encouraging results show that the design could be effectively exploited in the vast arsenic-affected rural areas of South-East Asian countries blessed with abundant sunlight particularly during the critical dry season. Solar-driven membrane distillation has the potential of removing arsenic from contaminated groundwater.

PURPOSE OF REVIEW: Many of the highly populated and industrialized countries are paying more attention to green fuels. The conventional methods for biodiesel purification processes result in a large quantity of polluted water, leading to serious environmental concerns. To overcome the challenges in the existing process, addressing the membrane technology is a viable solution to direct further research toward sustainable membrane-based green production. RECENT FINDINGS: The developing membrane technology is an alternative method for eliminating wastewater during biodiesel production from conventional processes. This paper provides a comprehensive review of recent development applications of the catalytic membrane and membrane materials for high-quality biodiesel production. Both polymeric and ceramic membranes result in optimum performance of more than 90% effective conversion and purification. The catalytic membrane reactor integrates chemical reaction and product separation concurrently in a single device system to produce high-quality biodiesel. Glycerol purification of 99% was achieved in the potential membrane distillation process. This review critically summarizes biodiesel production and purification using membrane techniques and membrane reactors. Membrane material and separation efficiency were discussed in a short view. Besides, the significance of catalytic membrane reactor is outlined. Glycerol separation and purification by removal of water and other residual impurities were potentially achieved using membrane technology. Apart from applications of the membrane, the novel attempt of a combined description of influencing factors and limitations of the membrane during biodiesel production was revealed. Therefore, membrane applications in high-grade biodiesel and value-added byproduct production are the predominant green technological approach for next-generation biofuels.

Osmotic membrane bioreactor (OMBR), which integrates forward osmosis (FO) with biological treatment process, has been recently developed to advance wastewater treatment and reuse. During OMBR operation, driven by osmotic pressure gradient, biologically treated water transports from the mixed liquor, through a semi-permeable FO membrane, into a highly concentrated draw solution. Compared to conventional MBR, OMBR has several advantages, including better product water quality, lower fouling propensity, and higher fouling reversibility. OMBR can be operated in the osmotic dilution mode when the draw solution, such as liquid fertilizers or seawater, can be reused or discharged directly. In most cases, OMBR is integrated with an additional process, commonly including reverse osmosis, membrane distillation, and electrodialysis, to form hybrid systems for sustainably reconcentrating draw solutions and producing clean water for reuse. In addition, several membrane processes, such as microfiltration, ultrafiltration, and electrodialysis, are combined with OMBR to address its inherent issue, salinity build-up in the bioreactor, and achieve resource (e.g., nutrients and energy) recovery. This review aims to provide a comprehensive understanding on the performance of OMBR and its hybrid systems in wastewater reuse and resource recovery. OMBR analogs and their performance are also systematically introduced. Key technical challenges and their potential solutions to the further development of OMBR and its hybrid systems are highlighted. This review sheds light on future research for the further development of OMBR and its hybrid systems.

PURPOSE OF REVIEW: Membrane distillation (MD) has been known as a promising water treatment process for many years. However, despite its advantages, MD has never been able to compete with other processes for industrial water treatment and supply. Instead, it has been orientated towards several unique strategic water treatment applications. This review aims to uncover the opportunities and technical challenges pertinent to the MD process and the current status of its strategic water treatment applications most notably including decentralised small-scale desalination for fresh water provision in remote areas, hybridisation with forward osmosis (FO) for treatment of challenging polluted waters, regeneration of liquid desiccant solutions for air conditioning, and treatment of acid effluents for beneficial reuse. RECENT FINDINGS: Pilot and small-scale MD systems have been demonstrated for decentralised desalination using various renewable energy sources to supply fresh water in remote, rural areas and on ships where other desalination processes are inefficient or unfeasible. For this strategic desalination application, MD is technically viable, but more works on configuration modification and process optimisation are required to reduce the process energy consumption and water production costs. For the three other strategic applications, the technical viability of the MD process has been proved by extensive lab-scale researches, but its economic feasibility is still questionable due to the lack of large-scale evaluation and the uncertain costs of MD systems. The orientation of MD towards strategic water treatment applications is clear. However, huge efforts are required to facilitate these applications at commercial and full scale.

PURPOSE OF REVIEW: Membrane techniques have been employed to concentrate livestock manure effluent from anaerobic digestion to produce highly concentrated liquid organic fertilizer. This review aims to provide a comprehensive understanding on the opportunities and challenges of membrane processes in the concentration of digested effluent for their further implementation. RECENT FINDINGS: Anaerobic digestion has been deployed to convert livestock manure into biogas (energy) and digestate with high potential as biofertilizer. Digestate can be separated into a solid and liquid fraction to reduce required capacity for onsite storage. The liquid fraction, known as digested effluent, remains a vexing challenge to digestate management due to the contradiction between its continuous production and seasonal application to farmlands, particularly in developing countries. Recent investigation has demonstrated the promise of membrane techniques for the concentration of digested effluent to recover recycling water and produce nutrient-rich liquid fertilizer. These techniques mainly include hydraulically driven membrane processes (from microfiltration to reverse osmosis), forward osmosis, membrane distillation, and electrodialysis. In most cases, these membrane techniques are hybridized to enhance the concentration efficiency. Nevertheless, the practical application of these membrane processes is hindered by several technical challenges, which mainly include membrane fouling, contaminant enrichment, ammonia volatilization, and high economic input. In this paper, we critically reviewed the performance of different membrane processes in the concentration of digested livestock manure effluent. Key technical challenges and their potential countermeasures were elucidated. Furthermore, future perspectives were provided to shed light on further development of membrane concentration techniques in the field.

Seawater and brackish water desalination has been a practical approach to mitigating the global fresh water scarcity. Current large-scale desalination installations worldwide can complementarily augment the global fresh water supplies, and their capacities are steadily increasing year-on-year. Despite substantial technological advance, desalination processes are deemed energy-intensive and considerable sources of CO₂ emission, leading to the urgent need for innovative low carbon desalination platforms. This paper provides a comprehensive review on innovations in membrane processes and membrane materials for low carbon desalination. In this paper, working principles, intrinsic attributes, technical challenges, and recent advances in membrane materials of the membrane-based desalination processes, exclusively including commercialised reverse osmosis (RO) and emerging forward osmosis (FO), membrane distillation (MD), electrodialysis (ED), and capacitive deionisation (CDI), are thoroughly analysed to shed light on the prospect of low carbon desalination.

The primary aim of this research was to identify the physicochemical properties of the oil and water-in-oil (W/O) emulsions used during a NOFO Oil-on-Water field trials that reduced the performance of the skimmers recovery efficacy during the trials. Extensive studies were performed at SINTEF laboratories with the residues of oil topped (i.e. evaporative loss of crude oil components by distillation process at large scale) for the field trial and compared it with different residues of oil topped by bench scale laboratory procedures. In order to obtain a sufficient stable W/O emulsion for the field trial, bunker fuel oil (IFO380) and various concentrations of an emulsifier (Paramul®) were also added to the residues of oil topped on large scale and investigated through interfacial tension, contact angle, droplet adhesion and “dip and withdraw” tests. The investigations revealed that the addition of an emulsifier lowered the interfacial tension of oil residues, which consequently reduced the adherence properties of the oil and emulsions to the surface of the skimmer material. Too high concentration of an emulsifier (>0,5%) also had a negative effect on the stability of W/O emulsion.