Enhancing electrokinetics and desalination efficiency through catalysts and electrode modifications in microbial desalination cells.

Microbial desalination cells (MDCs) are considered as a sustainable technology for water desalination, wastewater treatment, and power generation. However, this neoteric technology suffers from different challenges, including sluggish oxygen reduction reaction and poor electron transfer from microbes to electrodes, ultimately leading to less power generation and desalination efficiency. This review delves into the intricate roles of both abiotic and biocatalysts in enhancing performance of MDCs through ion removal and charge transfer mechanisms. Detailed discussions highlight the comparative advantages and limitations of different catalyst types and insights into electrode modifications to optimise catalytic activity and biofilm formation. Further, recent advancements in electrode engineering, including surface coatings and integration of nanomaterial, geared towards enhancing efficiency of MDC and performance stability are discussed. Finally, future recommendations are provided, focusing on innovative catalyst designs, material integration, and considerations for scale-up and commercialisation, thereby offering a comprehensive roadmap for the continued advancement of MDC.

Effective method for upcycling construction and demolition waste into concrete: A life cycle approach.

Different property enhancement techniques have already been established to support upcycling of construction and demolition waste as aggregate in concrete. However, the most suitable and sustainable method is still unknown. Quality improvement of recycled coarse aggregate (RCA) after any treatment method and its environmental impact is estimated using life cycle analysis (LCA). This article compares the environmental impacts of such treatment methods on RCA and aims to find out the most suitable method with minimum impacts. The functional unit of this study is considered the preparation of 1 tonne of treated aggregate (recycled), considering reduction in water absorption after the treatment. An LCA is carried out using the SimaPro software (https://simapro.com/) followed by ISO 14040/44 guidelines. Based on the LCA environmental profiles, thermal treatment is the highest emission contributing removal method followed by mechanical grinding. In strengthening of attached mortar methods, accelerated carbonation process is the major emission contributing method followed by a specific microbial treatment. Moreover, a sensitivity analysis was performed by varying the energy mix with a focus on renewable-based energy mix. The sensitivity analysis shows a shift on selection for the suitable treatment method and other possibilities considering renewable-based energy mix. A preliminary assessment and probable impact prediction could be conceptualized before the adoption of any treatment method on RCA for a particular location.

Carbon material produced by hydrothermal carbonisation of food waste as an electrode material for supercapacitor application: A circular economy approach.

This study aims to use landfill leachate (LL) as an aqueous medium during hydrothermal carbonisation (HTC) of food waste to produce hydrochar (FWH-LL-C), which could be used as an electrode material in energy storage devices. The structural properties and electrochemical performance of the hydrochar were compared to that obtained using distilled water as a reaction medium (FWH-DW-C). The results showed that there is a difference in Brunauer-Emmett-Teller (BET) surface area of FWH-LL-C (220 m2 gm-1) and FWH-DW-C (319 m2 gm-1). The electrochemical properties were comparable, with FWH-LL-C having 227 F g-1 specific capacitance at 1 A g-1 current density and FWH-DW-C having 235 F g-1 specific capacitance at 1 A g-1 current density. Furthermore, at a power density of 634 W kg-1, FWH-DW-C achieved the highest energy density of 14.4 Wh kg-1. The energy retention capacity of the electrode was 98% which indicate that the material has an excellent energy storage capacity. The findings suggested that LL could be used as an alternative source of aqueous media during the HTC of food waste to produce hydrochar which could be used as an effective electrode material in supercapacitors.

Challenges, opportunities, and innovations for effective solid waste management during and post COVID-19 pandemic.

The crisis brought upon by the COVID-19 pandemic has altered global waste generation dynamics and therefore has necessitated special attention. The unexpected fluctuations in waste composition and quantity also require a dynamic response from policymakers. This study highlights the challenges faced by the solid waste management sector during the pandemic and the underlying opportunities to fill existing loopholes in the system. The study presents specific cases for biomedical waste, plastic waste, and food waste management - all of which have been a major cause of concern during this crisis. Further, without active citizen participation and cooperation, commingled virus-laden biomedical waste with the regular solid waste stream pose significant negative health and safety issues to sanitation workers. Single-use plastic usage is set to bounce back due to growing concerns of hygiene, particularly from products used for personal protection and healthcare purposes. It is expected that household food waste generation may reduce due to increased conscious buying of more non-perishable items during lockdown and due to concerns of food shortage. However, there is a chance of increase in food waste from the broken supply chains such as food items getting stuck on road due to restriction in vehicle movements, lack of workers in the warehouse for handling the food products, etc. The study also stresses the need for building localized resilient supply chains to counter such situations during future pandemics. While offering innovative solutions to existing waste management challenges, the study also suggests some key recommendations to the policymakers to help handle probable future pandemics if any holistically.

A novel risk assessment method for landfill slope failure: Case study application for Bhalswa Dumpsite, India.

Rapid population growth of major urban centres in many developing countries has created massive landfills with extraordinary heights and steep side-slopes, which are frequently surrounded by illegal low-income residential settlements developed too close to landfills. These extraordinary landfills are facing high risks of catastrophic failure with potentially large numbers of fatalities. This study presents a novel method for risk assessment of landfill slope failure, using probabilistic analysis of potential failure scenarios and associated fatalities. The conceptual framework of the method includes selecting appropriate statistical distributions for the municipal solid waste (MSW) material shear strength and rheological properties for potential failure scenario analysis. The MSW material properties for a given scenario is then used to analyse the probability of slope failure and the resulting run-out length to calculate the potential risk of fatalities. In comparison with existing methods, which are solely based on the probability of slope failure, this method provides a more accurate estimate of the risk of fatalities associated with a given landfill slope failure. The application of the new risk assessment method is demonstrated with a case study for a landfill located within a heavily populated area of New Delhi, India.

Validation of QuEChERS method for the determination of 36 pesticide residues in fruits and vegetables from Ghana, using gas chromatography with electron capture and pulsed flame photometric detectors.

In this study, "Quick, Easy, Cheap, Effective, Rugged and Safe" 'QuEChERS' method was modified for the determination of 36 pesticides fortified at (0.01-1.0) mg kg(-1) in three vegetables and a fruit (lettuce, carrot, tomatoes and pineapples respectively) from Ghana. The method involved extraction with acetonitrile, phase separation with primary secondary amine and magnesium sulfate; the final injection solution was reconstituted in ethyl acetate. Organochlorine and synthetic pyrethroids residues were detected with electron capture detector whereas organophosphorus, pulsed flame photometric detector was used. The recoveries at different concentration levels (0.01, 0.1 and 1.0 mg kg(-1)) were in the range of 83% and 93% with relative standard deviation ranging from 2% to 10% (n = 5) and the coefficient of determination (R(2)) was greater than 0.99 for all the 36 pesticides. The method was successfully tested on 120 real samples from Accra markets and this proved to be useful for monitoring purposes particularly in laboratories that have no gas chromatography-mass spectrometry and liquid chromatography-mass spectrometry.

Effect of moisture control and air venting on H2S production and leachate quality in mature C&D debris landfills.

The effect of air venting and moisture variation on H2S production and the leaching of metals/metalloids (arsenic, copper, chromium, and boron) from treated wood in aged mature construction and demolition (C&D) debris landfills were examined. Three simulated C&D debris landfill lysimeters were constructed and monitored, each containing as a major debris component either wooden pallets, chromated copper arsenate (CCA) treated wood, or alkaline copper quaternary (ACQ) treated wood. The lysimeters were operated with alternating periods of water addition (a total of 160 L in four equal amounts) and air venting (68.4 m(3)per day for 121 days in two phases). Moisture addition did not increase H2S levels in the long term, and a significant drop in H2S concentration was observed (up to 99%) when aerobic conditions were promoted through air venting. H2S concentrations increased after venting stopped up to values approximately two orders of magnitude lower than observed prior to venting. Venting had the immediate consequence of suppressing biological H2S production, and the longer-term effect of decreasing organic matter that could otherwise be utilized in this process. Under aerobic conditions, the levels of arsenic, chromium, and boron in leachate decreased up to 96%, 49%, and 68%, respectively, while copper was found to increase up to 200% in CCA and 445% in ACQ column leachates.

Effect of solution chemistry on the sedimentation, dissolution, and aggregation of the bimetallic Fe/Cu nanoparticles pre- and post-grafted with carboxymethyl cellulose.

The suitability of iron-based nanomaterials or composites for in-situ remediation hinges on their physicochemical stability. Introducing surface modifications like metal doping or polymer grafting can regulate interparticle forces, influencing particle stability. Thus, probing how grafting methods (i.e., pre- or post-grafting) tune material properties controlling interparticle forces, comprehend the synergistic effect of metal doping and polymer grafting, and evaluate stability under varying geochemical conditions are the way forward in designing sustainable remediation strategies. To this end, time-dependent sedimentation, dissolution, and aggregation of four synthesized iron-based nanoparticles (bare iron (Fe), copper doped bimetallic iron/copper (Fe/Cu), pre- and post-grafted Fe/Cu with carboxymethyl cellulose (CMC) - CMCpre-Fe/Cu and CMCpost-Fe/Cu, respectively) were carried out as a function of solution chemistry (i.e., pH - 5 to 10, ionic strength, IS - 0 to 100 mM NaCl, initial particle concentration, C0-20 to 200 mg.L-1) mimicking geoenvironmental conditions. CMCpre-Fe/Cu exhibited markedly higher particle availability (> 91 %) against sedimentation than others (bare Fe/Cu (11.28 %) > bare Fe (7.33 %) > CMCpost-Fe/Cu (6.09 %)) - suggesting the pivotal role of grafting method on particle stability. XDLVO energy profiles revealed pre-grafting altered magnetic properties favoring surface charge-driven electrostatic repulsion over magnetic attraction, thereby limiting aggregation-induced particle settling. In contrast, superior magnetic force overrides the electrostatic behavior for bare and post-grafted particles. Unlike bare and post-grafted nanoparticles, CMCpre-Fe/Cu aggregate size correlated positively with [H+] and IS, consistent with their settling behavior. Rise in C0 showed a visible negative effect on particle aggregation and, thereby, sedimentation except for CMCpre-Fe/Cu by facilitating particle collision through Brownian movement. Both acidic pH and copper doping promoted nanoparticle dissolution, whereas pre-grafting can provide a plausible solution against nanoparticle toxicity and loss of reactivity due to ionic release. To recapitulate, these findings are imperative in building a sustainable framework for environmental remediation application.

Simultaneous ammonia and organics degradation from municipal landfill leachate by electrochemical oxidation.

The two primary issues for wide implementation of the electrochemical oxidation of wastewater are the significant cost of electrode and high energy consumption. On the other side, conventional biological processes and membrane technology have several drawbacks for recalcitrant landfill leachate (LL) treatment. To address these issues, graphite/PbO2 anode was used to treat medium to mature age (biodegradability index, 5-day biochemical oxygen demand/chemical oxygen demand: 0.25) LL. To reduce the cost of the oxidation process and maximize the efficiency, operating conditions were optimized. The optimum parameter values were obtained as 24.7 mA cm-2, 180 ± 3 rpm, and 1.9 cm of current density, stirring rate, and electrode gap, respectively. Dissolved organic carbon (DOC), chemical oxygen demand (COD), and ammonia-N removal efficiencies of 55 ± 1.4%, 81 ± 1.9%, and 56 ± 3% were obtained after 8 h of degradation at optimum conditions. The decrease in aromatic substances and ultraviolet (UV) quenching materials were evaluated by UV-Visible spectroscopy and Specific UV absorbance. The conversion of aromatic compounds into simpler molecule compounds was also verified by Fourier-transform infrared spectroscopy analysis. The lab-scale anode synthesis cost was evaluated as 0.42 USD.

Progress and perspectives on carbon-based materials for adsorptive removal and photocatalytic degradation of perfluoroalkyl and polyfluoroalkyl substances (PFAS).

Per- and polyfluoroalkyl substances (PFAS) (also known as 'forever chemicals') have emerged as trace pollutants of global concern, attributing to their persistent and bio-accumulative nature, pervasive distribution, and adverse public health and environmental impacts. The unregulated discharge of PFAS into aquatic environments represents a prominent threat to the wellbeing of humans and marine biota, thereby exhorting unprecedented action to tackle PFAS contamination. Indeed, several noteworthy technologies intending to remove PFAS from environmental compartments have been intensively evaluated in recent years. Amongst them, adsorption and photocatalysis demonstrate remarkable ability to eliminate PFAS from different water matrices. In particular, carbon-based materials, because of their diverse structures and many exciting properties, offer bountiful opportunities as both adsorbent and photocatalyst, for the efficient abatement of PFAS. This review, therefore, presents a comprehensive summary of the diverse array of carbonaceous materials, including biochar, activated carbon, carbon nanotubes, and graphene, that can serve as ideal candidates in adsorptive and photocatalytic treatment of PFAS contaminated water. Specifically, the efficacy of carbon-mediated PFAS removal via adsorption and photocatalysis is summarised, together with a cognizance of the factors influencing the treatment efficiency. The review further highlights the neoteric development on the novel innovative approach 'concentrate and degrade' that integrates selective adsorption of trace concentrations of PFAS onto photoactive surface sites, with enhanced catalytic activity. This technique is way more energy efficient than conventional energy-intensive photocatalysis. Finally, the review speculates the cardinal challenges associated with the practical utility of carbon-based materials, including their scalability and economic feasibility, for eliminating exceptionally stable PFAS from water matrices.

Co-pyrolysis of plastic waste and eucalyptus waste wood for fuel pellets production: A study of fuel, mechanical, and combustion characteristics under varying binder proportion.

The study explores the effect of varying molasses proportions as a binder on the characteristics of densified char obtained through the slow co-pyrolysis of plastic waste and Eucalyptus wood waste (Waste low-density polyethylene - Eucalyptus wood (WLDPE-EW) and Waste Polystyrene - Eucalyptus wood (WPS-EW)). Pyrolysis was conducted at 500 °C with a residence time of 120 min, employing plastic to wood waste ratios of 1:2 and 1:3 (w/w). The focus was on how varying the proportion of molasses (10-30 %), influences the physical and combustion properties of the resulting biofuel pellets. Our findings reveal that the calorific value of the pellets decreased from 28.94 to 27.44 MJ/Kg as the molasses content increased. However, this decrease in calorific value was compensated by an increase in pellet mass density, which led to a higher energy density overall. This phenomenon was attributed to the formation of solid bridges between particles, facilitated by molasses, effectively decreasing particle spacing. The structural integrity of the pellets, as measured by the impact resistance index, improved significantly (43-47 %) with the addition of molasses. However, a significant change in the combustion characteristics depicted by lower ignition and burnout temperatures were observed due to decrease in fixed carbon value and increase in volatile matter content, as the proportion of molasses increased. Despite these changes, the pellets demonstrated a stable combustion profile, suggesting that molasses are an effective binder for producing biofuel pellets through the densification of char derived from the co-pyrolysis of plastic and Eucalyptus wood waste. The optimized molasses concentration analyzed through multifactor regression analysis was 16.96 % with 28 % WLDPE proportion to produce WLDPE-EW char pellets. This study highlights the potential of using molasses as a sustainable binder to enhance the mechanical and combustion properties of biofuel pellets, offering a viable pathway for the valorization of waste materials.

PDA-Fe3O4 decorated carbon felt anode enhancing electrochemical performance of microbial fuel cells: Effect of electrode materials on electroactive biofilm.

Anode modification is an effective strategy for enhancing the electrochemical performance of microbial fuel cell (MFC). However, the impacts of the modified materials on anode biofilm development during MFC operation have been less studied. We prepared a novel PDA-Fe3O4-CF composite anode by coating original carbon felt anode (CF) with polydopamine (PDA) and Fe3O4 nanoparticles. The composite anode material was characterized by excellent hydrophilicity and electrical conductivity, and the anodic biofilm exhibited fast start-up, higher biomass, and more uniform biofilm layer after MFC operation. The MFC reactor assembled with the composite anode achieved a maximum power density of 608 mW m-2 and an output voltage of 586 mV, which were 316.4% and 72.4% higher than the MFC with the original CF anode, respectively. Microbial community analysis indicated that the modified anode biofilm had a higher relative abundance of exoelectrogen species in comparison to the unmodified anode. The PICRUSt data revealed that the anodic materials may affect the bioelectrochemical performance of the biofilm by influencing the expression levels of key enzyme genes involved in biofilm extracellular polymer (EPS) secretion and extracellular electron transfer (EET). The growth of the anodic biofilm would exert positive or negative influences on the efficiency of electricity production and electron transfer of the MFCs at different operating stages. This work expands the knowledge of the role that anodic materials play in the development and electrochemical performance of anodic biofilm in MFCs.

From slag to green: Aided-phytoremediation as a sustainable tool to rehabilitate land contaminated by steel slag and assessment of CO2 sequestration.

Steel slag (SS) has many applications, but its immediate reuse is not possible due to its inherent swelling potential and presence of toxic metals. Therefore, it can only be used after the aging process, which can be either natural or artificial. While few large-scale steel plants afford artificial aging, many small-scale ones opt for natural aging through stockpiling of SS. This results in an increase in soil pH to over 12, thus damaging the ecosystem and making it unviable for plant growth. This research focuses on the reclamation of land affected by SS through the formation of a Phyto-barrier using 22 native plant species aided by the application of a 2 % (v/v) solution of the organic amendment. Furthermore, the superior performance of plants belonging to the Fabaceae family was ascertained, while establishing Sesbania grandiflora as an able species for aided-phytoremediation due to its remarkable growth (≈ 10 ft tall and 33 cm in circumference) during the study period. The CO2 sequestered by the plantation showed that maximum sequestration has been done by Sesbania grandiflora (49.96 kg CO2 / tree/ year), and least by Azadirachta indica (0.35 kg CO2/tree/year). The overall CO2 sequestered by the plantation stood at 3.85 tons/year. A cost-benefit analysis of using aided-phytoremediation indicates an expense of 90 $ per year as the recurring expense, while carbon credits if monetized, would yield 154 $ to 308 $ as returns. The investigations of this study established a new approach to vegetation over SS-affected land, through native species and the application of organic amendment.

Impacts of select organic ligands on the colloidal stability, dissolution dynamics, and toxicity of silver nanoparticles.

Key understanding of potential transformations that may occur on silver nanoparticle (AgNP) surface upon interaction with naturally ubiquitous organic ligands (e.g., -SH (thoil), humic acid, or -COO (carboxylate)) is limited. Herein we investigated how dissolved organic carbon (DOC), -SH (in cysteine, a well-known Ag(+) chelating agent), and -COO (in trolox, a well-known antioxidant) could alter the colloidal stability, dissolution rate, and toxicity of citrate-functionalized AgNPs (citrate-AgNPs) against a keystone crustacean Daphnia magna. Cysteine, DOC, or trolox amendment of citrate-AgNPs differentially modified particle size, surface properties (charge, plasmonic spectra), and ion release dynamics, thereby attenuating (with cysteine or trolox) or promoting (with DOC) AgNP toxicity. Except with DOC amendment, the combined toxicity of AgNPs and released Ag under cysteine or trolox amendment was lower than of AgNO3 alone. The results of this study show that citrate-AgNP toxicity can be associated with oxidative stress, ion release, and the organism biology. Our evidence suggests that specific organic ligands available in the receiving waters can differentially surface modify AgNPs and alter their environmental persistence (changing dissolution dynamics) and subsequently the toxicity; hence, we caveat to generalize that surface modified nanoparticles upon environmental release may not be toxic to receptor organisms.

Biochar-mediated removal of pharmaceutical compounds from aqueous matrices via adsorption.

Pharmaceutical is one of the noteworthy classes of emerging contaminants. These biologically active compounds pose a range of deleterious impacts on human health and the environment. This is attributed to their refractory behavior, poor biodegradability, and pseudopersistent nature. Their large-scale production by pharmaceutical industries and subsequent widespread utilization in hospitals, community health centers, and veterinary facilities, among others, have significantly increased the occurrence of pharmaceutical residues in various environmental compartments. Several technologies are currently being evaluated to eliminate pharmaceutical compounds (PCs) from aqueous environments. Among them, adsorption appears as the most viable treatment option because of its operational simplicity and low cost. Intensive research and development efforts are, therefore, currently underway to develop inexpensive adsorbents for the effective abatement of PCs. Although numerous adsorbents have been investigated for the removal of PCs in recent years, biochar-based adsorbents have garnered tremendous scientific attention to eliminate PCs from aqueous matrices because of their decent specific surface area, tunable surface chemistry, scalable production, and environmentally benign nature. This review, therefore, attempts to provide an overview of the latest progress in the application of biochar for the removal of PCs from wastewater. Additionally, the fundamental knowledge gaps in the domain knowledge are identified and novel strategic research guidelines are laid out to make further advances in this promising approach towards sustainable development.

Environmental impact evaluation of landfill mining of legacy waste with on-site sorting using life cycle assessment.

The present research is aimed at assessing the environmental impacts of landfill mining of soil-like material with on-site sorting for land application using life cycle assessment. The scenario is compared with no-landfill mining (base scenario) and future scenario (including material recycling and incineration). Soil-like material is processed using windrow composting. The impact assessment was performed using the EASETECH™ software tool. ReCipE 2016 midpoint world impact method with eight impact categories was used for assessing the environmental profiles. The functional unit of the assessment was 1 t of recovered waste in India. Overall, the results showed that excavation of landfilled waste with on-site recovery of soil and land application of soil resulted in higher environmental benefits compared to no mining condition in global warming potential (GWP), freshwater eutrophication (FEW), human toxicity (HT), and fossil depletion (FD), while higher impacts were observed in terrestrial acidification (TA), terrestrial ecotoxicity (TE), marine eutrophication (ME), and photochemical oxidation (PCO). After composting, land application of recovered soil contributed to environmental offsets in GWP, HT, and FEW while contributing to TE emissions. Emissions associated with excavation and on-site sorting contributed 55.1% to freshwater toxicity, 25.5% to human toxicity, 16.2% to climate change, and 10.8% to terrestrial acidification. The choice of energy, transportation, and fuel for waste activities affected the performance of alternative scenarios in GWP. Application of recovered metals in the manufacturing process, incineration of plastic, and textile components improved the environmental performance. The outcomes of this research will equip regulatory bodies in the development of guidelines and frameworks on material and energy recovery from the waste components mined from legacy waste.

A review on the scope of remediating chlorinated paraffin contaminated water bodies and soils/sediments.

Chlorinated paraffins (CPs) involve a wide range of complex mixtures of chlorinated alkanes. The versatility of their physicochemical properties and their wide range of use has turned them into ubiquitous materials. This review covers the scope of remediating CP-contaminated water bodies and soil/sediments via thermal, photolytic, photocatalytic, nanoscale zero-valent iron (NZVI), microbial and plant-based remediation techniques. Thermal treatments above 800 °C can lead to almost 100 % degradation of CPs by forming chlorinated polyaromatic hydrocarbons and thus should be supported with appropriate pollution control measures leading to high operational and maintenance costs. The hydrophobic nature of CPs lowers their water solubility and reduces their subsequent photolytic degradation. However, photocatalysis can have considerably higher degradation efficiency and generates mineralized end products. The NZVI also showed promising CP removal efficiency, especially at lower pH, which is challenging to achieve during field application. CPs can also be bioremediated by introducing both naturally occurring bacteria and also by engineered bacterial strains which are capable of producing specific enzymes (like LinA2 and LinB) to catalyze CP degradation. Depending on the type of CP, bioremediation can even achieve a dechlorination efficiency of >90 %. Moreover, enhanced degradation rates can be achieved through biostimulation. Phytoremediation has also exhibited CP bioaccumulation and transformation tendencies, both at lab-scale and in field-scale studies. The future research scope can include developing more definitive analytical techniques, toxicity and risk assessment studies of CPs and their degradation products, and technoeconomic and environmental assessment of different remediation approaches.

Life cycle assessment of fermentative production of lactic acid from bread waste based on process modelling using pinch technology.

Bread waste (BW), a rich source of fermentable carbohydrates, has the potential to be a sustainable feedstock for the production of lactic acid (LA). In our previous work, the LA concentration of 155.4 g/L was achieved from BW via enzymatic hydrolysis, which was followed by a techno-economic analysis of the bioprocess. This work evaluates the relative environmental performance of two scenarios - neutral and low pH fermentation processes for polymer-grade LA production from BW using a cradle-to-gate life cycle assessment (LCA). The LCA was based on an industrial-scale biorefinery process handling 100 metric tons BW per day modelled using Aspen Plus. The LCA results depicted that wastewater from anaerobic digestion (AD) (42.3-51 %) and cooling water utility (34.6-39.5 %), majorly from esterification, were the critical environmental hotspots for LA production. Low pH fermentation yielded the best results compared to neutral pH fermentation, with 11.4-11.5 % reduction in the overall environmental footprint. Moreover, process integration by pinch technology, which enhanced thermal efficiency and heat recovery within the process, led to a further reduction in the impacts by 7.2-7.34 %. Scenario and sensitivity analyses depicted that substituting ultrapure water with completely softened water and sustainable management of AD wastewater could further improve the environmental performance of the processes.

Synthesis and commercialization of bioplastics: Organic waste as a sustainable feedstock.

Substituting synthetic plastics with bioplastics, primarily due to their inherent biodegradable properties, represents a highly effective strategy to address the current global issue of plastic waste accumulation in the environment. Advances in bioplastic research have led to the development of materials with improved properties, enabling their use in a wide range of applications in major commercial sectors. Bioplastics are derived from various natural sources such as plants, animals, and microorganisms. Polyhydroxyalkanoate (PHA), a biopolymer synthesized by bacteria through microbial fermentation, exhibits physicochemical and mechanical characteristics comparable to those of synthetic plastics. In response to the growing demand for these environmentally friendly plastics, researchers are actively investigating various cleaner production methods, including modification or derivatization of existing molecules for enhanced properties and new-generation applications to expand their market share in the coming decades. By 2026, the commercial manufacturing capacity of bioplastics is projected to reach 7.6 million tonnes, with Europe currently holding a significant market share of 43.5 %. Bioplastics are predominantly utilized in the packaging industry, indicating a strong focus of their application in the sector. With the anticipated rise in bioplastic waste volume over the next few decades, it is crucial to comprehend their fate in various environments to evaluate the overall environmental impact. Ensuring their complete biodegradation involves optimizing waste management strategies and appropriate disposal within these facilities. Future research efforts should prioritize exploration of their end-of-life management and toxicity assessment of degradation products. These efforts are crucial to ensure the economic viability and environmental sustainability of bioplastics as alternatives to synthetic plastics.

Composite of graphitic carbon nitride and TiO2 as photo-electro-catalyst in microbial fuel cell.

The widespread application of surfactants and their subsequent discharge in the receiving water bodies is a very common issue in developing countries. In the present investigation, a composite of graphitic carbon nitride (GCN) and TiO2 was used as a photo-electro-catalyst in a microbial fuel cell (MFC)-based hybrid system for bio-electricity production and simultaneous pollutant removal (organic matter and sodium dodecyl sulphate, SDS). The GCN: TiO2 composite with a ratio of 70:30 (by wt. %) revealed a better electrochemical response; thus, it was used as a photo-electro-catalyst in MFC. Additionally, the photochemical characterization indicated a decrease in the band gap and charge recombination of GCN-TiO2 composite compared to standalone TiO2, which indicated a conducive effect of GCN addition. Further, on the actual use as a photo-electro-catalyst, the GCN-TiO2 catalysed MFC attained 58.2 ± 9.6% and 86.5 ± 7.1% of COD and SDS removal; while simultaneously harvesting a maximum power density of 1.07 W m-3, which was higher than standalone TiO2-catalysed MFC. The follow-up treatment in the charcoal bio-filter and photo-cathodic chamber of the hybrid system further improved the overall COD and SDS removal efficiency to 92.1 ± 2.7 and 95.6 ± 1.5%, respectively. The electro-catalytic performance of the GCN-TiO2 can be attributed to the presence of nitrogen-active species in the composite. The results of this investigation demonstrated a potential MFC-based hybrid system for the simultaneous secondary and tertiary treatment of municipal wastewater. Consequently, the outcome of this investigation indicates an innovative research direction in the field of photo-electro-catalyst, which can fit into the role of a photo-catalyst as well as an electro-catalyst.