Synthesis and application of manganese-doped zinc oxide as a potential adsorbent for removal of Congo red dye from wastewater.

Synthetic dyes are considered toxic compounds and as such are not easily removed by conventional water treatment processes. This study demonstrated the synthesis of pure and manganese- (Mn), silver- (Ag), and iron- (Fe) doped zinc oxide (ZnO) nanoparticles via the wet chemical route. In particular, it investigated the batch adsorption studies and physiochemical properties of synthesized pure and doped ZnO materials for removing toxic congo red (CR) dye. X-ray diffraction (XRD), Raman spectroscopy, and energy-dispersive X-ray spectroscopy (EDS) confirmed the synthesis of the pure and doped ZnO materials. The batch adsorption investigation revealed adsorption efficiencies of 99.4% for CR dye at an optimal dose of 0.03 g/30 ml for Mn-doped ZnO at a solution pH of 2. The adsorption capacity of each of the synthesized materials was found to be in order Mn-doped ZnO (232.5 mg/g) > Ag-doped ZnO (222.2 mg/g) > pure ZnO (212.7 mg/g) > Fe-doped ZnO (208.3 mg/g). Both pseudo-second-order kinetics model and the Langmuir isotherm model accurately explained the adsorption behaviors of CR dye. As such, Van der Waal interactions, H-bonding, and electrostatic interaction were found to be the adsorption mechanisms responsible for dye removal. In addition, the desorption-regeneration investigation indicated the successful reuse of the exhausted Mn-doped ZnO material for five cycles of CR dye adsorption with an efficiency of 83.1%. Overall, this study has demonstrated that Mn-doped ZnO could be considered a viable adsorbent for the cleanup of dye-contaminated water.

Role of water shear force for microplastics fragmentation into nanoplastics.

Wastewater treatment plants (WWTPs) are major recipients of microplastics (MPs) that break down into nanoplastics (NPs) during wastewater treatment through physical, chemical, and biological processes. In particular, mechanical stress induced by the mixing process commonly used in WWTPs is thought to play a crucial role in the production of secondary MPs/NPs, which are then discharged into the open water environment through the WWTP effluent. This study investigated the fragmentation of 250 and 106 µm-sized pristine and weathered polystyrene (PS) particles using a four-blade mechanical impeller. At an energy density level of 100 kJ/L, the 250 and 106 µm-sized pristine PS particles were broken down into mean sizes of 120.6 ± 19.1 and 95.6 ± 16.8 nm, respectively. The smallest sizes were found to be 90.9 ± 17.8 and 72.4 ± 19.6 nm due to the breakdown of 250 and 106 µm-sized weathered PS particles, respectively. The morphology of the PS particles after fragmentation also demonstrated the initiation of surface damage, such as cracks, pores and rough structures. This surface crack propagation, caused by mechanically induced water shear force, was identified as the primary mechanism of MP fragmentation into NPs. It was also found that NP levels significantly increased after 40 min of mixing, with at least a 28-fold increase in water solution at an energy density of 32 kJ/L. These results clearly show that the breakdown of MPs into NPs is a continuous process during wastewater treatment, posing a significant threat to the water environment through NP release by WWTP effluents.

Performance of biochar mixed cement paste for removal of Cu, Pb and Zn from stormwater.

Using biochar as a partial replacement of Portland cement in cementitious materials is a promising solution to mitigate negative environmental impacts. However, current studies in available literature primarily focus on the mechanical properties of composites made with cementitious materials and biochar. Therefore, this paper reports the effects of the type of biochar, the percentage of biochar addition, and the particle size of the biochar on the removal efficiency of Cu, Pb, and Zn, as well as the effect of contact time on the removal efficiency of Cu, Pb, and Zn, along with the compressive strength. The peak intensities of OH-, CO32- and Calcium Silicate Hydrate (Ca-Si-H) peaks increase with increasing biochar addition levels, reflecting increased hydration product formation. The reduction of particle size of biochar causes the polymerization of the Ca-Si-H gel. However, no significant changes were observed in heavy metal removal, irrespective of the percentage of biochar addition, the particle size of biochar, or the type of biochar added to the cement paste. Adsorption capacities above 19 mg/g, 11 mg/g and 19 mg/g for Cu, Pb and Zn were recorded in all composites at an initial pH of 6.0. The Pseudo second order model best described the kinetics of the Cu, Pb, and Zn removal. The rate of adsorptive removal increases with the decrease in the density of the adsorbents. Over 40% of Cu and Zn were removed as carbonates and hydroxides through precipitation, whereas over 80% of Pb removal was via adsorption. Heavy metals bonded with OH-, CO32- and Ca-Si-H functional groups. The results demonstrate that biochar can be used as a cement replacement without negatively impacting heavy metal removal. However, neutralization of the high pH is needed before safe discharge.

Resource recovery from RO concentrate using nanofiltration: Impact of active layer thickness on performance.

Modelling the removal of monovalent and divalent ions from seawater via nanofiltration is crucial for pre-treatment in seawater reverse osmosis systems. Effective separation of divalent ions through nanofiltration and allowing the permeate containing only monovalent ions to pass through the reverse osmosis system produces pure NaCl salt from the concentrate. However, the Donnan steric pore model and dielectric exclusion assume a uniformly distributed cylinder pore morphology, which is not representative of the actual membrane structure. This study analyzed the impact of membrane thickness on neutral solute removal and investigated the effect of two different methods for calculating the Peclet number on rejection rates of monovalent and divalent salts. Results show that membrane thickness has a significant effect on rejection rates, particularly for uncharged solutes in the range of 0.5-0.7 solute radius to membrane pore size ratio. Operating pressures above 10 bar favour the use of effective active layer thickness over the membrane pore size to calculate the Peclet number. At low pressures, using the effective active layer can lead to overestimation of monovalent salt rejection and underestimation of divalent salt rejection. This study highlights the importance of appropriate Peclet number calculation methods based on applied pressure when modelling membrane separation performance.

Conversion of pyrolytic non-condensable gases from polypropylene co-polymer into bamboo-type carbon nanotubes and high-quality oil using biochar as catalyst.

The conversion of low-value plastic waste into high-value products such as carbon nanomaterial is of recent interest. In the current study, the non-condensable pyrolysis gases, produced from Polypropylene Copolymer (PPC) feedstock, was converted into bamboo-type carbon nanotubes (BCNTs) through catalytic chemical vapour deposition using biochar. Experiments were conducted in a three-zone furnace fixed bed reactor, where PPC was pyrolysed in the second zone and carbon nanotubes (CNTs) growth was eventuated in the third zone. The effects of different growth temperatures (500, 700, 900 °C) and biochar particle sizes (nanoparticle as well as 0-100 and 100-300 µm) were investigated to optimise the production of hydrogen and the yield of carbon nanotubes on the biochar surface. Biochar samples used in the synthesis of CNTs were obtained from the pyrolysis of saw dust at 700 °C in a muffle furnace. Analyses performed by using Scanning electron microscopy, Transmission electron microscopy, X-ray diffraction, and Raman spectroscopy techniques suggested that the best crystalline structure of CNTs were obtained at 900 °C with nano-sized biochar as a catalyst. The strong gas-solid contact and void fraction of nano-sized particles enhances the diffusion-precipitation mechanism, leading to the growth of CNTs. The nano-sized biochar increased hydrogen production at 900 °C and reduced the polycyclic aromatic hydrocarbons content in oil to only 1%, which is advantageous for further utilisation. Therefore, the production of high-value CNTs from waste plastic using low-cost biochar catalyst can be a sustainable approach in the management of waste plastic while participating in the circular economy.

Reduction of excess sludge production by membrane bioreactor coupled with anoxic side-stream reactors.

While cleaning wastewater, biological wastewater treatment processes such as membrane bioreactors (MBR) produce a significant amount of sludge that requires costly management. In the oxic-settling-anoxic (OSA) process, sludge is retained for a temporary period in side-stream reactors with low oxygen and substrate, and then it is recirculated to the main reactor. In this way, excess sludge production is reduced. We studied the influence of the rate of sludge exchange between MBR and side-stream anoxic reactors on sludge yield reduction within MBR. Two MBRs, namely, MBROSA and MBRcontrol, each coupled with separate external anoxic side-stream reactors, were run in parallel for 350 days. Unlike MBRcontrol, MBROSA had sludge exchange with the external reactors connected to it. During the investigation over a sludge interchange rate (SIR) range of 0-22%, an SIR of 11% achieved the highest sludge reduction (58%). Greater volatile solids destruction i.e., bacterial cell lysis and extracellular polymeric substance (EPS) destruction occurred at the SIR of 11%, which helped to achieve the highest sludge reduction. The enhanced volatile solids destruction was evident by the release of nutrients in the external anoxic reactors. It was confirmed that the sludge yield reduction was achieved without compromising the wastewater treatment quality, sludge settleability and hydraulic performance of the membrane in MBR.

Effect of the coagulation/persulfate pre-treatment to mitigate organic fouling in the forward osmosis of municipal wastewater treatment.

The forward osmosis (FO) membrane process has recently established in many applications such as desalination, wastewater reuse, water purification, food processing, resource recovery and sustainable power generation. However, many researchers raise the demand for systematic investigation on FO membrane fouling, which leads to reduced flux yield. In this study, the effect of coagulation/persulfate as a feed pre-treatment was used to mitigate FO organic fouling during municipal wastewater treatment, and compared with a control coagulation and potassium persulfate pre-treatments. Mass balance results using size exclusion chromatography exhibited that the decrease in the flux with consecutive filtration cycles was likely due to humic-like molecules in the feedwater. Coagulation/persulfate contributed to a more significant flux improvement than stand-alone coagulation or persulfate pre-treatment, resulting in a smaller amount of organics attachment to the membrane. A better flux enhancement by coagulation/persulfate was again evidenced by a higher decrease in the attachment of reversible and irreversible organic foulants on the membrane surface. This study identified the major organic components responsible for FO fouling and established the potential of coagulation/persulfate pre-treatment for reducing organic fouling of FO membrane during municipal wastewater treatment.

Removal of arsenic and iron removal from drinking water using coagulation and biological treatment.

Effects of biological activated carbon (BAC), biological aerated filter (BAF), alum coagulation and Moringa oleifera coagulation were investigated to remove iron and arsenic contaminants from drinking water. At an initial dose of 5 mg/L, the removal efficiency for arsenic and iron was 63% and 58% respectively using alum, and 47% and 41% respectively using Moringa oleifera. The removal of both contaminants increased with the increase in coagulant dose and decrease in pH. Biological processes were more effective in removing these contaminants than coagulation. Compared to BAF, BAC gave greater removal of both arsenic and iron, removing 85% and 74%, respectively. Longer contact time for both processes could reduce the greater concentration of arsenic and iron contaminants. The addition of coagulation (at 5 mg/L dosage) and a biological process (with 15 or 60 min contact time) could significantly increase removal efficiency, and the maximum removal was observed for the combination of alum and BAC treatment (60 min contact time), with 100% and 98.56% for arsenic and iron respectively. The reduction efficiency of arsenic and iron reduced with the increase in the concentration of dissolved organics in the feedwater due to the adsorption competition between organic molecules and heavy metals.

Reactive layered hydroxide membrane for advanced water treatment: Micropollutant degradation and antifouling potential.

The effective removal of micropollutants by water treatment technologies remains a significant challenge. Herein, we develop a CoFe layered double hydroxide (CoFeLDH) catalytic membrane for peroxymonosulfate (PMS) activation to achieve efficient micropollutant removal with improved mass transfer rate and reaction kinetics. This study found that the CoFeLDH membrane/PMS system achieved an impressive above 98% degradation of the probe chemical ranitidine at 0.1 mM of PMS including five more micropollutants (Sulfamethoxazole, Ciprofloxacin, Carbamazepine, Acetaminophen and Bisphenol A) at satisfactory level (above 80%). Moreover, significant improvements in water flux and antifouling properties were observed, marking the membrane as a specific advancement in the removal of membrane fouling in water purification technology. The membrane demonstrated consistent degradation efficiency for several micropollutants and across a range of pH (4-9) as well as different anionic environments, thereby showing it suitability for scale-up application. The key role of reactive species such as SO4•-, and O2• - radicals in the degradation process was elucidated. This is followed by the confirmation of the occurrence of redox cycling between Co and Fe, and the presence of CoOH+ that promotes PMS activation. Over the ten cycles, the membrane could be operated with a flux recovery of up to 99.8% and maintained efficient performance over 24 h continuous operation. Finally, the efficiency in degrading micropollutants, coupled with reduced metal leaching, makes the CoFeLDH membrane as a promising technology for application in water treatment.

Bio-corrosion in concrete sewer systems: Mechanisms and mitigation strategies.

The deterioration of concrete sewer structures due to bio-corrosion presents critical and escalating challenges from structural, economic and environmental perspectives. Despite decades of research, this issue remains inadequately addressed, resulting in billions of dollars in maintenance costs and a shortened service life for sewer infrastructure worldwide. This challenge is exacerbated by the absence of standardized test methods and universally accepted mitigation strategies, leaving industries and stakeholders confronting an increasingly pressing problem. This paper aims to bridge this knowledge gap by providing a comprehensive review of the complex mechanisms of bio-corrosion, focusing on the formation and accumulation of hydrogen sulfide, its conversion into sulfuric acid and the subsequent deterioration of concrete materials. The paper also explores various factors affecting bio-corrosion rates, including environmental conditions, concrete properties and wastewater characteristics. The paper further highlights existing corrosion test strategies, such as chemical tests, in-situ tests and microbial simulations tests along with their general analytical parameters. The conversion of hydrogen sulfide into sulfuric acid is a primary cause of concrete decay and its progression is influenced by environmental conditions, inherent concrete characteristics, and the composition of wastewater. Through illustrative case studies, the paper assesses the practical implications and efficacy of prevailing mitigation techniques. Coating materials provide a protective barrier against corrosive agents among the discussed techniques, while optimised concrete mix designs enhance the inherent resistance and durability of the concrete matrix. Finally, this review also outlines the future prospects and challenges in bio-corrosion research with an aim to promote the creation of more resilient and cost-efficient materials for sewer systems.

Effectiveness of grease interceptors in food service establishments for controlling fat, oil and grease deposition in the sewer system.

The water industry worldwide experiences numerous sewer blockages each year, partially attributed to the accumulation of fat, oil and grease (FOG). Managing this issue involves various strategies, including the requirement for installation of grease interceptors (GIs) installation. However, the claimed efficacy of commercial GIs of eliminating 99 % of FOG has been questioned for many years because FOG deposit formation occurs despite food service establishments (FSEs) using GIs, therefore detailed understanding of FOG wastewater compositions and its removal by GIs is required. This study provides an insight into the key FOG components such as FOG particle size, metals and fatty acid (FA) profile in GI influent and effluent, and within the GI, at three different FSEs. Analysis of FAs identified substantial proportions of extra-long-chain FAs in the effluents, including arachidic (C20:0), behenic (C22:0), mead (C20:3), lignoceric (C24:0), and nervonic (C24:1) acids. In contrast, the household kitchen released palmitic (C16:0), oleic (C18:1) and linoleic (C18:2) acids. It was further observed that scums effectively remove the larger FOG particles, leaving only 10 % below 75.4 µm. Notably, FSEs which employed automatic dishwashers produced up to 80.4 % of particles ≤45 µm, whereas FSEs and household kitchen which used handwash sinks generated only 36.9 % and 26.3 % of particles ≤45 µm, respectively. This study demonstrated that the commercial GIs do not remove FOG entirely but clearly demonstrated that they discharge high concentrations of FOG with extra-long FFAs which were attributed to the occurrence of microbial activity and hydrolysis of triglycerides within the GI, potentially contributing to FOG deposition.

Understanding the risk of using herbicides for tree root removal into wastewater treatment plant performance.

Adding herbicides to sewer lines, a common practice for controlling root intrusion in sewer pipes, may adversely impact downstream wastewater treatment by inhibiting nitrification and denitrification performance. This study investigated the effects of herbicides, namely diquat, triclopyr, and 2-methyl-4-chlorophenoxyacetic acid (MCPA)-dicamba, on these processes. Various parameters were monitored, including oxygen uptake rate (OUR), nutrients (NH3-N, TP, NO3-N, and NO2-N), chemical oxygen demand (COD), and herbicide concentrations. It was found that nitrification was not affected by OUR in the presence of each herbicide at various concentrations (1, 10, and 100 mg L-1). Additionally, MCPA-dicamba at various concentrations demonstrated minimal inhibition in the nitrification process compared to diquat and triclopyr. COD consumption was not affected by the presence of these herbicides. However, triclopyr significantly inhibited NO3-N formation in the denitrification process at various concentrations. Similar to nitrification process, both COD consumption and herbicide reduction concentration were not affected by the presence of herbicides during the denitrification process. Adenosine triphosphate measurements showed minimal impact on nitrification and denitrification processes when herbicides were present in the solution up to a concentration of 10 mg L-1. Tree root kill efficiency experiments were performed on Acacia melanoxylon. Considering the performance on nitrification and denitrification process, diquat emerged as the best herbicide option (concentration of 10 mg L-1), with a 91.24% root kill efficiency.

Green synthesis of zinc oxide nanoparticles using lychee peel and its application in anti-bacterial properties and CR dye removal from wastewater.

In nanoscience and nanobiotechnology, using plant extracts in synthesizing metal nanoparticles (NPs) has recently come to light as an exciting opportunity with several benefits over traditional physicochemical methods. In the present work, zinc oxide (ZnO) based nanoparticles (NPs) were synthesized by green chemistry route using lychee peel extract to capture hazardous congo red dye from wastewater and illustrate their antimicrobial behavior. The X-Ray Diffraction (XRD) spectra confirm the wurtzite crystal structure, and Fourier Transform Infrared (FTIR) spectra confirm the functional group in ZnO, which is suitable for dye adsorption. It was found that the NPs were spherical and had a size of <10 nm. The synthesized ZnO NPs could effectively remove >98% of CR dye from wastewater within 120 min of contact time at a wide pH range from 2 to 10. The primary mechanism involved in removing dye was the electrostatic interaction between ZnO adsorbent and CR dye. The antimicrobial performance of synthesized ZnO NPs was found to show 34% inhibition against Bacillus subtilis (ATCC 6538), 52% against Escherichia coli (ATCC 11103), 58% against Pseudomonas aeruginosa (ATCC 25668) and 32% against Staphylococcus aureus (ATCC 25923) using well diffusion assay. ZnO demonstrates a suitable anti-bacterial property over both gram-positive and gram-negative pathogenic bacteria. Overall, the green synthesized method for developing ZnO NPs shows promising and significant anti-bacterial performance and is a highly potential adsorbent for removing CR dye from wastewater.

Tackling fat, oil, and grease (FOG) build-up in sewers: Insights into deposit formation and sustainable in-sewer management techniques.

The increasing global demand for fatty products, population growth, and the expansion of food service establishments (FSEs) present significant challenges for the wastewater industry. This is often due to the build-up of fat, oil and grease (FOG) in sewers, which reduces capacity and leads to sanitary sewer overflows. It is crucial to develop economic and sustainable in-sewer FOG management techniques to minimise maintenance costs and service disruptions caused by the removal of FOG deposits from sewers. This study aims to understand the process of FOG deposit formation in both concrete and non-concrete sewers. Compared to fresh cooking oil, disposal of used cooking oil in households and FSE sinks results in the formation of highly adhesive and viscous FOG deposits. This occurs due to hydrolysis during frying, which increases the concentration of fatty acids, particularly palmitic acid, in the used cooking oil. Furthermore, metal ions from food waste, wastewater, and dishwashing detergents contribute to the saponification and aggregation reactions which cause FOG deposition in both concrete and non-concrete sewers. However, the leaching of Ca2+ ions exacerbates FOG deposition in cement-concrete sewers. The article concludes by suggesting future research perspectives and proposes implementation strategies for microbially induced concrete corrosion (MICC) control to manage FOG deposition in sewers. One such strategy involves applying superhydrophobic coating materials with low surface free energy and high surface roughness to the interior surfaces of the sewer. This approach would help repel wastewater carrying FOG deposit components, potentially disrupting the interaction between FOG components, and reducing the adhesion of FOG deposits to sewer surfaces.

Component analysis of fat, oil and grease in wastewater: challenges and opportunities.

The presence of fat, oil and grease can lead to blockages in sewer lines, pumps, and treatment plant operations, thereby creating health risks and environmental hazards. These deposits primarily consist of fatty acids, triglycerides and soap, among other components. These three main components are hydrophobic and insoluble in water. The composition of FOG can vary significantly depending on the source, such as food service establishments, households, or industrial processes. Several analytical methods, such as chromatographic, gravimetric, chemical and spectroscopic analysis, are used to measure different FOG components. AOAC, Gerber and APHA are the most commonly utilized standardized analytical methods for measuring FOG components. The AOAC and Gerber methods, which use gas chromatography, tend to provide more accurate results compared to other methods. This can be attributed to GC's ability to measure individual fatty acids in FOG samples by separating and quantifying each compound based on its unique chemical properties, such as volatility, polarity and molecular weight. Similarly, high-performance liquid chromatography is capable of measuring glycerides by separating and quantifying them based on their polarity and molecular weight. This article delves into the challenge of accurately measuring FOG concentrations and evaluates various FOG measurement technologies. The study also discusses the need for standardized methods for FOG measurement, highlighting the importance of understanding FOG deposits and the performance of grease interceptors.

Fast and Effective Removal of Congo Red by Doped ZnO Nanoparticles.

ZnO nanoparticles (NPs) show remarkable efficiency in removing various contaminants from aqueous systems. Doping ZnO NPs with a second metal element can dramatically change the physicochemical properties of the pristine nanoparticles. However, there have been limited reports on the absorption of doped ZnO NPs, especially comparing the performance of ZnO NPs with different doping elements. Herein, ZnO NPs were doped with three transitional metals (Co, Fe, and Mn) at a nominal 2 wt.%. The particle surface had a higher dopant concentration than the interior for all NPs, implying the migration of the dopants to the surface. Because doping atoms inhibited grain growth, the doped ZnO NPs had a small particle size and a large surface area. The adsorption performance followed the order of Fe-doped < undoped < Mn-doped < Co-doped ZnO. Co-doped ZnO had an increased surface area and less tendency to agglomerate in an aqueous solution, showing the best adsorption performance. The adsorption of Congo red (CR) on Co-doped ZnO followed the pseudo-second-order model and the Langmuir isotherm. The adsorption process was spontaneous through monolayer chemisorption, and the maximum adsorption capacity was 230 mg/g. Finally, the Co-doped ZnO was successfully incorporated into an alginate membrane by electrospinning. The membrane demonstrated excellent adsorption performance and had great potential as an innovative and low-cost adsorbent (inexpensive raw materials and simple processing) for wastewater purification.

Nano and microplastics occurrence in wastewater treatment plants: A comprehensive understanding of microplastics fragmentation and their removal.

Nano/microplastic (NP/MP) pollution is a growing concern for the water environment. Wastewater treatment plants (WWTPs) are considered the major recipients of MP before discharging into local waterbodies. MPs enter WWTPs mainly from synthetic fibers through washing activities and personal care products. To control and prevent NP/MP pollution, it is essential to have a comprehensive understanding of their characteristics, fragmentation mechanisms, and the effectiveness of the current treatment processes used in WWTPs for NP/MP removal. Therefore, the objectives of this study are to (i) understand the detailed mapping of NP/MP in the WWTP, (ii) understand the fragmentation mechanisms of MP into NP, and (iii) investigate the removal efficiency of NP/MP by existing processes in the WWTP. This study found that fiber is the dominant shape of MP, and polyethylene, polypropylene, polyethylene terephthalate, and polystyrene are the major polymer type of MP in wastewater samples. Crack propagation and mechanical breakdown of MP due to water shear forces induced by treatment facilities (e.g., pumping, mixing, and bubbling) could be the major causes for NP generation in the WWTP. Conventional wastewater treatment processes are ineffective for the complete removal of MPs. Although these processes are capable of removing ∼95% of MPs, they tend to accumulate in sludge. Thus, a significant number of MPs may still be released into the environment from WWTPs on a daily basis. Therefore, this study suggested that using DAF process in the primary treatment unit can be an effective strategy to control MP in the initial stage before it goes to the secondary and tertiary stage.

Unlocking the potential of sulphide tailings: A comprehensive characterization study for critical mineral recovery.

Sulphide tailings are a major environmental concern due to acid mine drainage and heavy metal leaching, with costly treatments that lack economic benefits. Reprocessing these wastes for resource recovery can address pollution while creating economic opportunities. This study aimed to evaluate the potential for critical mineral recovery by characterizing sulphide tailings from a Zn-Cu-Pb mining site. Advanced analytical tools, such as electron microprobe analysis (EMPA) and scanning electron microscopy (SEM)-based energy dispersive spectroscopy (EDS), were utilized to determine the physical, geochemical, and mineralogical properties of the tailings. The results showed that the tailings were fine-grained (∼50 wt% below 63 µm) and composed of Si (∼17 wt%), Ba (∼13 wt%), and Al, Fe, and Mn (∼6 wt%). Of these, Mn, a critical mineral, was analyzed for recovery potential, and it was found to be largely contained in rhodochrosite (MnCO3) mineral. The metallurgical balance revealed that ∼93 wt% of Mn was distributed in -150 + 10 µm size fractions containing 75% of the total mass. Additionally, the mineral liberation analysis indicated that Mn-grains were primarily liberated below 106 µm size, suggesting the need for light grinding of above 106 µm size to liberate the locked Mn minerals. This study demonstrates the potential of sulphide tailings as a source for critical minerals, rather than being a burden, and highlights the benefits of reprocessing them for a resource recovery to address both environmental and economic concerns.

Development of a ZnOS+C Composite as a Potential Adsorbent for the Effective Removal of Fast Green Dye from Real Wastewater.

Wastewater treatment is becoming increasingly important due to the potential shortage of pure drinking water in many parts of the world. Adsorption offers a potential technique for the uptake of contaminants and wastewater purification. In the last two decades, several efforts have been made to remove fast green (FG) dye from wastewater via different adsorbent materials. However, adsorption capacity shown by these adsorbents is low and time-consuming. Herein, we have synthesized for the first time a new powdered adsorbent ZnOS+C, modified zinc peroxide with sulfur and activated carbon to effectively remove FG dye from wastewater. Results of batch adsorption experiments have suggested that ZnOS+C has the maximum adsorption potential of 238.28 mg/g for FG dye within 120 min of adsorption equilibrium for a wide range of pH ranging from 2 to 10 pH. The adsorption process conforms to the Freundlich isotherm model, suggesting a multilayered adsorption process on the outer surface of ZnOS+C. The adsorption kinetics study indicates that the kinetics of the reaction are the intraparticle diffusion model. Briefly, this study shows proof of the application of ZnOS+C powder as a new eco-friendly adsorbent with extremely high efficiency and high surface area for removing FG dye.

Responses of syntrophic microbial communities and their interactions with polystyrene nanoplastics in a microbial electrolysis cell.

Microbial electrochemical technologies are promising for simultaneous energy recovery and wastewater treatment. Although the inhibitory effects of emerging pollutants, particularly micro/nanoplastics (MPs/NPs), on conventional wastewater systems have been extensively studied, the current understanding of their impact on microbial electrochemical systems is still quite limited. Microplastics are plastic particles ranging from 1 µm to 5 mm. However, nanoplastics are smaller plastic particles ranging from 1 to 100 nm. Due to their smaller size and greater surface area, they can penetrate deeper into biofilm structures and cell membranes, potentially disrupting their integrity and leading to changes in biofilm composition and function. This study first reports the impact of polystyrene nanoplastics (PsNPs) on syntrophic anode microbial communities in a microbial electrolysis cell. Low concentrations of PsNPs (50 and 250 µg/L) had a minimal impact on current density and hydrogen production. However, 500 µg/L of PsNPs decreased the maximum current density and specific hydrogen production rate by ∼43 % and ∼48 %, respectively. Exposure to PsNPs increased extracellular polymeric substance (EPS) levels, with a higher ratio of carbohydrates to proteins, suggesting a potential defense mechanism through EPS secretion. The downregulation of genes associated with extracellular electron transfer was observed at 500 µg/L of PsNPs. Furthermore, the detrimental impact of 500 µg/L PsNPs on the microbiome was evident from the decrease in 16S rRNA gene copies, microbial diversity, richness, and relative abundances of key electroactive and fermentative bacteria. For the first time, this study presents the inhibitory threshold of any NPs on syntrophic electroactive biofilms within a microbial electrochemical system.