Effect of multi-interface electron transfer on water splitting and an innovative electrolytic cell for synergistic hydrogen production and degradation

The cleaning and utilization of industry wastewater are still a big challenge. In this work, we mainly investigate the effect of electron transfer among multi-interfaces on water electrolysis reaction. Typically, the CoS2, Co3S4/CoS2 (designated as CS4-2) and Co3S4/Co9S8/CoS2 (designated as CS4-8-2) samples are prepared on a large scale by one-step molten salt method. It is found that because of the different work functions (designated as WF; WF(Co3S4) = 4.48eV, WF(CoS2) = 4.41eV, WF(Co9S8) = 4.18 eV), the effective heterojunctions at the multi-interfaces of CS4-8-2 sample, which obviously improve interface charge transfer. Thus, the CS4-8-2 sample shows an excellent oxygen evolution reaction (OER) activity (134 mV/10 mA cm-2, 40 mV dec-1). The larger double-layer capacitance (Cdl = 17.1 mF cm-2) of the CS4-8-2 sample indicates more electrochemical active sites, compared to the CoS2 and CS4-2 samples. Density functional theory (DFT) calculation proves that due to interface polarization under electric field, the multi-interfaces effectively promote electron transfer and regulate electron structure, thus promoting the adsorption of OH- and dissociation of H2O. Moreover, an innovative norfloxacin (NFX) electrolytic cell (EC) is developed through introducing NFX into the electrolyte, in which efficient NFX degradation and hydrogen production are synergistically achieved. To reach 50 mA cm-2, the required cell voltage of NFX-EC has decreased by 35.2%, compared to conventional KOH-EC. After 2h running at 1 V, 25.5% NFX was degraded in the NFX EC. This innovative NFX-EC is highly energy-efficient, which is promising for the synergistic cleaning and utilization of industry wastewater.

Toward a greener future: A survey on sustainable blockchain applications and impact

Blockchain Technology has garnered significant attention due to its immense potential to transform the way transactions are conducted and information is managed. Blockchain is a decentralized digital ledger that is spread across a network of computers, ensuring the secure, transparent, and unchangeable recording of transactions. However, the energy consumption of certain blockchain networks like Bitcoin, Litecoin, Monero, Zcash, and others has generated apprehensions regarding the sustainability of this technology. Bitcoin alone consumes approximately 100 terawatt-hours annually, contributing significantly to global carbon emissions. The substantial energy requirements not only contribute to carbon emissions but also pose a risk to the long-term viability of the blockchain industry. This study reviews articles from eight reputable databases between 2017 to August 2023, employing the systematic review and preferred reporting items for systematic reviews and meta-analyses approach for screening. Therefore, explore the applications of sustainable blockchain networks aimed at reducing environmental impact while ensuring efficiency and security. This survey also assesses the challenges and limitations posed by diverse blockchain applications regarding sustainability and provides valuable foresight into potential future advancements. Through this survey, the aim is to track and verify sustainable practices, facilitating the transition to a low-carbon economy, and promoting environmental stewardship, with a specific focus on highlighting the potential of sustainable blockchain networks in enabling secure and transparent tracking of these practices. Finally, the paper sheds light on pertinent research challenges and provides a roadmap of future directions, stimulating further research in this promising field.

Sulphate reduction, mixed sulphide- and thiosulphate-driven Autotrophic denitrification, NItrification, and Anammox (SANIA) integrated process for sustainable wastewater treatment

This study proposes the Sulphate reduction, mixed sulphide- and thiosulphate-driven Autotrophic denitrification, Nitrification, and Anammox integrated (SANIA) process for sustainable treatment of mainstream wastewater after organics capture. Three moving-bed biofilm reactors (MBBRs) were applied for developing sulphate reduction (SR), mixed sulphide- and thiosulphate-driven partial denitrification and Anammox (MSPDA), and NItrification (N), respectively. Typical mainstream wastewater after organics capture (e.g., chemically enhanced primary treatment, CEPT) was synthesized with chemical oxygen demand (COD) of 110 mg/L, sulphate of 50 mg S/L, ammonium of 30 mgN/L. The feasibility of SANIA was investigated with mimic nitrifying effluent supplied in MSPDA-MBBR (Period I), followed by the examination of the applicability of SANIA process with N-MBBR integrated (Period II), under moderate temperatures (25-27 ℃). In Period I, SANIA process was established with both SR- and MSPDA-MBBR continuously operated for over 300 days (no Anammox biomass inoculation). Specifically, in MSPDA-MBBR, high rates of denitratation (2.7 gN/(m2·d)) and Anammox (2.8 gN/(m2·d)) were achieved with Anammox contributing to 81 % of the total inorganic nitrogen removal. In Period II, the integrated SANIA system was continuously operated for over 130 days, achieving up to 90 % of COD, 93 % of ammonium, and 61 % of total inorganic nitrogen (TIN) removal, with effluent concentrations lower than 10 mg COD/L, 3 mg NH4+-N/L, and 13 mg TIN-N/L. The implementation of SANIA can ultimately reduce 75 % and 40 % of organics and aeration energy for biological nitrogen removal. Considering the combination of SANIA with CEPT for carbon capture and sludge digestion/incineration for energy recovery, the new integrated wastewater technology can be a promising strategy for sustainable wastewater treatment.

Room temperature synthesis of monolithic MIL-100(Fe) in aqueous solution for energy-efficient removal and recovery of aromatic volatile organic compounds

The removal and recovery of volatile organic compounds (VOCs) are widely used in many industrials. Unfortunately, most conventional porous materials not only have low VOCs uptake, but also need to be regenerated at relatively high temperature. Metal-organic frameworks (MOFs) have great potential for the removal and recovery of VOCs as their record-breaking gas adsorption capacity, easy regeneration, tunable pore structure and functional groups. Whereas, powdered MOFs are hardly implemented in industrial fields owing to their low bulk density and high pressure drop. Exploring a green method to prepare granular MOFs for the removal and recovery of VOCs is still a challenge. Herein, we report the room temperature green synthesis of a stable Fe-based MOF monolith by using water as the solvent without applying high pressure and chemical binders. The static and dynamic experiments show that the optimized centimeter-scale monolith has high porosity and mechanical strength, and exhibits much better adsorption performance for representative aromatic VOCs (benzene, toluene and p-xylene), than commercial activated carbon and activated carbon fiber under the same conditions. Remarkably, as-synthesized monolith can be rapidly regenerated at lower temperature. These results clearly demonstrate the advantages of MOF monoliths in removing and recovering VOCs, and also provide new insight into the effects of drying temperature, washing and centrifugation procedures on MOF shaping.

Energy-efficient recovery of fermented butyric acid using octyl acetate extraction

Background

A butyric acid recovery process using octyl acetate is proposed, and the design details of the extraction and subsequent distillation processes were investigated. Ternary equilibrium data for the extractor design were derived from molecular simulations and experimental measurements.

Results

A new procedure for estimating the thermodynamic parameters was introduced to determine the effect of the parameters on extractor design by comparison with previously reported parameters. Using the proposed recovery process with the newly estimated thermodynamic model, 99.8% butyric acid was recovered from the fermentation broth at a recovery rate of 99%. The energy demand for the proposed process was found to be lower than the average demand for several reported butyric acid recovery processes.

Conclusions

The investment cost is projected to be lower than that of other butyric acid processes due to the high efficiency of extraction solvent. The recovery cost of butyric acid was comparable to its selling price.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13068-022-02146-6.

Rethinking electricity consumption and economic growth nexus in Turkey: environmental pros and cons

The critical role of electricity consumption in influencing and reshaping the economic and environmental landscape of the global economy cannot be underestimated. Electricity is the most beneficial and commonly transformed energy source; however, the strength, weakness, opportunities and threat of its consumption require scientific scrutiny. This study investigates electricity-led growth hypothesis vis-à-vis its impact on economic growth and environmental quality of Turkey. The annual time series data set from 1970 to 2014 were employed in the analysis with a battery of unit root and stationary tests. The equilibrium relationship in the study is explored using Maki and Bayer-Hanck combined cointegration tests under multiple structural breaks along with the Pesaran's ARDL bounds test procedure for robust check. The study confirms the existence of cointegration relationship between electricity consumption, economic growth, capital, labour and ecological footprint. To detect the direction of causal relations, the VECM Granger causality test is employed. The causality analysis provides empirical evidence that supports the electricity-induced growth hypothesis in Turkey. This implies that embarking on conservative energy-efficient policies will slow down Turkey's economic growth. Thus, precautionary measures that ensure adequate policy on energy mix to guarantee availability and accessibility to modern electricity will sustain economic growth and improve environmental sustainability.

The path from geology to indoor radon

It is generally accepted that radon emission is strongly influenced by the geological characteristics of the bedrock. However, transport in-soil and entry paths indoors are defined by other factors such as permeability, building and architectural features, ventilation, occupation patterns, etc. The purpose of this paper is to analyze the contribution of each parameter, from natural to man-made, on the radon accumulation indoors and to assess potential patterns, based on 100 case studies in Romania. The study pointed out that the geological foundation can provide a reasonable explanation for the majority of the values recorded in both soil and indoor air. Results also showed that older houses, built with earth-based materials, are highly permeable to soil radon. Energy-efficient houses, on the other hand, have a tendency to disregard the radon potential of the geological foundation, causing a higher predisposition to radon accumulation indoors and decreasing the general indoor air quality.

Novel energy-efficient electrodialysis system for continuous brackish water desalination: Innovative stack configurations and optimal inflow modes

Electrodialysis (ED) is a well-established brackish water (BW) desalination technology that has been commercially applied for decades. However, the energy efficiency of BWED cannot approach optimization because of the low salt concentration of BW. In this study, a novel two hydraulic-stage ED desalination system was presented to enhance mass transfer and reduce energy consumption. In terms of energy-efficient strategies, it involved not only innovative membrane stack configurations (resin-filled electrode cells and asymmetric cell pairs design) but also optimizing inflow modes (electrolytes parallel flow and dilute/concentrate counter flow). Results showed that thin resin-filled (1 mm) electrode cells, asymmetric cell pair design (cell pairs ratio of 1st and 2nd-hydraulic stages, 1.2), and optimizations of general inflow mode were beneficial for savings 10-30% of energy consumption at the same salt removal ratio (SR). The synergistic effects of these strategies indicated that this novel ED system could save ∼40% of the energy consumption at the same SR, compared with conventional two hydraulic-stage ED system (CED). Three stage continuous BWED performance tests, compared with a CED, showed that a 36.9% total energy saving could be achieved using the novel ED system when the BW concentration decreased from 3500 mg/L to the quality requirement of drinking water (∼450 mg/L). It was therefore possible to open the way for saving energy in BWED systems.

A modular functionalized anode for efficient electrochemical oxidation of wastewater: Inseparable synergy between OER anode and its magnetic auxiliary electrodes

Oxygen evolution reaction (OER) anodes, (e.g., IrO₂) are well-known inefficient catalysts for electrochemical oxidation (EO) of refractory organics in wastewater due to the high energy consumption via OER. However, in this study this kind of anode participated in a very effective EO process via a specific modular anode architecture. Traces of magnetic Fe₃O₄/Sb-SnO₂ particles as auxiliary electrodes (AEs) were attracted on the surface of the two-dimensional (2D) Ti/IrO₂-Ta₂O₅ by a NdFeB magnet, and thereby constituted a new magnetically assembled electrode (MAE). MAE could be renewed by recycling its AEs. The electrochemical properties as well as the EO performances of the MAE could be regulated by adjusting the loading amount of AEs. Results showed that even a small amount of AEs could increase surface roughness and offer massive effective active sites. When removing color of azo dye Acid Red G, the optimal MAE exhibited ∼1100 % and ∼500 % higher efficiencies than 2D Ti/IrO₂-Ta₂O₅ and 2D Ti/Sb-SnO₂, respectively. The superiority of the MAE was also applicable in degrading phenol. The synergy between Ti/IrO₂-Ta₂O₅ and magnetic Sb-SnO₂ particles was therefore discussed.

Selective conversion of polystyrene into renewable chemical feedstock under mild conditions

The aim of this work is to prepare catalysts for energy efficient conversion of polystyrene (PS) and its waste into valuable products with high conversion at 250 °C. The FeCo/Alumina bimetallic catalyst was synthesized by aqueous impregnation and structurally determined using scanning-transmission electron microscopy, temperature programmed desorption, X-ray diffraction, and X-ray photoelectron spectroscopy. Successfully, we have achieved up to 91% liquid yield with selectivities for styrene monomer (SM) up to 45 wt% and ethylbenzene (EB) up to 55 wt%, depending on the exposure time at 250 °C by FeCo/Alumina which is comparable to those of reactions at high temperatures (≥350 °C). Further increase of catalyst loadings from 200 to 400 mg also led to the decrease in styrene yield and increase in ethylbenzene yield. The analysis of the resulting clear liquid by gas chromatography/mass spectrometry (GC/MS) indicates the generation of products in the gasoline range.

Mainstream anammox in a novel A-2B process for energy-efficient municipal wastewater treatment with minimized sludge production

The conventional biological processes for municipal wastewater are facing the challenges of high energy consumption and production of excessive sludge. To address these two emerging issues, this study demonstrated the feasibility to integrate mainstream anammox into an A-2B process for municipal wastewater treatment towards energy-efficient operation with reduced sludge production. In the proposed A-2B process, an anaerobic fixed bed reactor (AFBR) served as A-stage for COD capture, an anammox moving bed biofilm reactor (MBBR) was employed as B2-stage, which received effluent containing nitrite from a sequencing batch reactor (SBR) at B1-stage. The results showed that under the operation conditions studied, 58% of influent COD was converted methane gas at A-stage, and 87% total inorganic nitrogen (TIN) removal was achieved with the effluent TIN concentration of 6.5 mg/L. Moreover, it was shown that at least 75% of sludge reduction was obtained due to the COD capture at A-stage. The high-throughput sequencing analysis further revealed that Candidatus Kuenenia was the dominant genus responsible for the observed anammox at B2-stage MBBR. This study clearly demonstrated a novel process configuration for sustaining mainstream anammox for municipal wastewater reclamation towards energy-efficient operation with minimized sludge production.