Waste Sludge Research Articles

Stabilization of heavy metals in solid waste and sludge pyrolysis by intercalation-exfoliation modified vermiculite

Increasing amounts of solid waste and sludge have created many environmental management problems. Pyrolysis can effectively reduce the volume of solid waste and sludge, but there is still the problem of heavy metal contamination, which limits the application of pyrolysis in environmental management. The intercalated-exfoliated modified vermiculite (IEMV) by intercalators of sodium dodecylbenzene sulfonate, hexadecyltrimethylammonium bromide and octadecyltrimethylammonium bromide were used to control the release of Cd, Cr, Cu, Zn and Pb during pyrolysis process of sludge or solid waste. The retention of heavy metals in sludge was generally better than that in solid waste. The IEMV by octadecyltrimethylammonium bromide as the intercalator calcined 800 °C (STAB-800) was the best additive for heavy metal retention, and the retention of Cr, Cu and Zn was significantly better than that of Pb and Cd. Cr, Cu, Zn and Pb were at low risk, while Cd had considerable risk under certain circumstances. New models were proposed to comprehensively evaluate the results of the risk and forms of heavy metals, and the increasing temperature was beneficial in reducing the hazards of heavy metals by the addition of STAB-800. The reaction mechanism of heavy metals with vermiculite was revealed by simulation of reaction sites, Fukui Function and Frontier Molecular Orbital. Thermal activation-intercalated-exfoliated modified vermiculite (T-IEMV) is more reactive and had more active sites for heavy metals. Mg atoms and outermost O atoms are the main atoms for T-IEMV to react with heavy metals. The Cr, Cu and Zn have better adsorption capacity by T-IEMV than Pb and Cd. This study provides a new insight into managing solid waste and sludge and controlling heavy metal environmental pollution.

Utilisation of Waste Sludge from Drinking Water Treatment as a Filler Material in Hot Mix Asphalt.

This research investigated the suitability of using sludge from the treatment of drinking water in hot mix asphalt (HMA) as a filler material. The storage and environmental impact of sludge is an enormous problem, especially for countries with large populations. Two different types of sludges, ferric chloride (FC) and aluminium sulphate (AS), were used as a filler material in HMA. The Hamburg Wheel Tracking (HWT) test, which correlates with rutting, and the Indirect Tensile Strength (ITS) test, which indicates the moisture sensitivity of HMA, were carried out at the optimum bitumen content of the mixes to investigate the usability of sludge in HMA. The test results indicate the usability of FC and AS in HMA compared to the reference mixes. However, the AS type of sludge has better rutting resistance than the FC type. Although the results support the usability of both sludges in HMA, it should be noted that the increased cost of the mix containing sludges due to the combustion process and the increased bitumen content during application should be considered.

POLITICAL AND ECONOMIC ASPECTS OF INTEGRATED URBAN WATER RESOURCES MANAGEMENT (IUWRM) IN SEMARANG CITY INDONESIA

Purpose: This study aims to find out the aspects of politics and economics of integrated urban water resources management in Semarang City and their impact on the practices of qualities of water resources management. Methods: This research used the qualitative method and field research approach. The focus data are the regulation and the implementation of water resources management in Semarang City Indonesia. The data was drawn from documents and interview with some resource persons. Results and Conclusion: The study found that the city government, which should carry out the function of conserving water resources, actually polluted the Kaligarang River through one of its institutions: Local Water Drinking Company, “Tirta Moedal”. This company disposes of waste sludge containing aluminum metal directly into the river without any treatment processes that impacted in pollution in the river and causing siltation of the river downstream. Research implications: the enactment of the comprehensive and integrated water resources management will has a positive impact on the practices of water resources management in Semarang specifically and Indonesia and even world countries generally. The implementation of comprehensive and integrated water resources management will also support the achievement of the sustainable development Goal. Originality/value: Semarang City government must be supported to arrange a comprehensive and integrated water resources management (WRM) policy. There must be a clear legal law for the water resources management.

Recent Advancements in Biochar and its Composite for the Remediation of Hazardous Pollutants

Abstract: Biochar has garnered considerable attention in recent times due to its potential uses in the environmental field. In this study, we comprehensively examine and condense information on biochar production, characteristics, and adsorption mechanisms, with a focus on its economic applications for remediating hazardous contaminants. Our assessment is based on over 200 publications from the past decade. Biochar, a carbon-rich material, can be derived from various organic waste sources, such as food waste and urban sewage sludge. Researchers are particularly interested in biochar due to its high carbon content, cation exchange capacity, substantial specific surface area, and stable structure. We investigate how the physical and chemical properties of biochar may vary based on the feedstock used, providing a comprehensive overview of biochar and its composition for pollution remediation. The review also discusses common techniques such as gasification, hydrothermal carbonization, and pyrolysis used to produce biochar. We analyze current research on the mechanisms involved in pollutant treatment using biochar and its composites while also addressing future directions in biochar research.

Enhanced biodegradation of sulfamethoxazole by pyrogenic carbon derived from aquacultural waste sludge

Sulfamethoxazole (SMX) is a widely utilized antibiotic that exhibits a broad spectrum of antibacterial activity, but its inadvertent release into the environment poses a significant threat to human society. The inefficacy of SMX degradation in microbial pipelines constantly challenges the regulation of antibiotics, making it a pressing and compelling concern. Former research has demonstrated the enhancement of the waste sludge-derived materials on SMX biodegradation, but the impact of these materials on microbial behavior remains unclear. In this study, two pyrogenic carbon materials (FBC and RBC) were prepared from aquacultural waste sludge and its downstream river sediment, respectively, to collaborate with SMX degrading species, Alcaligenes sp., for highly efficient removal of SMX. The cells of Alcaligenes sp. successfully colonized onto the biocompatible surface of the materials, and this hybrid structure nearly doubled the SMX degradation efficiency of the group without the carbon materials. The transcriptome analysis revealed that the existence of carbon materials significantly upregulated the expression of SMX degrading-related genes, including metCF and paaCIK, which led to bond breaking and benzene ring breakdown for the degradation of sulfamethoxazole. This work provides new insights into the mechanisms and environmental significance of SMX degradation by microbial immobilization onto waste-derived carbon-rich materials.

The Potential of Ozonation to Reduce Impact of Waste Sludge-Entrapped Microplastics to Biogas Production

ABSTRACT Due to low degradability of plastic materials, high usage, and low cost, microplastics (MPs) is becoming ubiquitous environmental pollutant. Wastewater treatment plants (WWTP) are one of main sources, where most of the MPs from wastewaters ends in waste sludge. Anaerobic digestion is one of most promised techniques of waste sludge management. The aim of this paper was to evaluate the impact of polyethylene terephthalate (PET) and polypropylene (PP) microplastics in the waste sludge with and without ozonation as possible pretreatment, on biogas and methane production with OxiTop® method. In the first set of experiments, PET inhibited (up to 6% at 0.1 g L−1) or promoted (up to 3% at 1 g L−1) methane production but increased cumulative biogas production (up to 38% at 0.5 g L−1). PP inhibited methane production (up to 5% at 0.5 g L−1) but its impact on biogas production was dependent upon concentration of MPs added. In the second set of experiments, pretreatment of non-contaminated waste sludge by ozonation (3.54 gozone h−1) inhibited methane yield. Longer time of ozonation of PP-contaminated waste sludge reduced inhibition of methane yield, while in the case of PET-contaminated waste sludge, it was increased.

Performance Analysis of Waste Biomass Gasification and Renewable Hydrogen Production by Neural Network Algorithm

Abstract This study assesses renewable hydrogen production via gasification of residual biomass, using artificial neural networks (ANNs) for predictive modeling. The process uses residues from sugarcane and orange harvests, sewage sludge, corn byproducts, coffee remnants, eucalyptus remains, and urban waste. Simulation data from aspen plus® software predict hydrogen conversion from each biomass type, with a three-layer feedforward neural network algorithm used for model construction. The model showed high accuracy, with R2 values exceeding 0.9941 and 0.9931 in training and testing datasets, respectively. Performance metrics revealed a maximum higher heating value (HHV) of 18.1 MJ/kg for sewage sludge, the highest cold gas efficiency for urban and orange waste (82.2% and 80.6%), and the highest carbon conversion efficiency for sugarcane bagasse and orange residue (92.8% and 91.2%). Corn waste and sewage sludge yielded the highest hydrogen mole fractions (0.55 and 0.52). The system can reach relative exergy efficiencies from 24.4% for sugarcane straw residues to 42.6% for sugarcane bagasse. Rational exergy efficiencies reached from 23.7% (coffee waste) to 39.0% (sugarcane bagasse). This research highlights the potential of ANNs in forecasting hydrogen conversion and assessing the performance of gasification-based renewable hydrogen procedures using biomass wastes.

Coupling effects of sewage sludge and recycled fine aggregate on the properties of geopolymer recycled mortars

The utilization of sludge from sewage treatment plants, ground granulated blast furnace slag (GGBFS) and recycled fine aggregate (RFA) from demolition of abandoned buildings in the production of geopolymer recycled aggregate mortar (GRM) offers a sustainable solution to reduce Ordinary Portland cement (OPC) application, and to address the growing volume of municipal sludge and construction waste. This work aims to investigate the workability, mechanical performance and microstructure of GGBFS and sewage sludge ash (SSA) based alkali activated GRM. GGBFS and SSA based geopolymer was used to replace 100% of OPC and RFA was employed to substitute various proportions (0%, 15%, 30% and 50%) of natural fine aggregates (NFA). Influences of SSA and RFA content on the consistency, setting time, compressive strength and flexural strength of GRM were investigated. The geopolymerization products were characterized through scanning electron microscopy (SEM), x-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FT-IR) tests. Results show that the consistency value and setting time of GRM decrease when the SSA and RFA content increases. When SSA content is 10% and RFA content is 15% (S10R15 sample), sample's microstructure becomes more compact, displaying robust mechanical properties. And S10R15 sample attained an average 28-day compressive strength of 51.7 MPa and flexural strength of 7.2 MPa. This demonstrates that GRM exhibits satisfactory working performance, mechanical properties. This study is expected to offer more insights into the application of SSA and RFA.

Fuzzy-random robust flexible programming on sustainable closed-loop renewable energy supply chain

Photovoltaic (PV) systems have become a widely accepted method of harnessing solar energy in recent decades. In addition to the growing use of renewable energies are being used due to the depletion of fossil fuel supplies and the corresponding pollution generated by these non-renewable fuels. Since PV systems possess a limited lifespan, and are predicted to eventually become outdated, sustainability and recycling that should be incorporated into the structure of the solar system supply chain. The management of high and low moisture waste (H&LMW) is crucial due to its harmful environmental impacts, including sludge waste, carbon dioxide (CO2), and acid compounds. This study explores the integration of research on H&LMW and PV systems, focusing on energy generation from biogas, incineration power plants, and PV systems. In this respect, we propose a multi-objective mixed-integer programming model to construct a sustainable closed-loop renewable energy supply chain by considering forward and reverse flow through solar, biogas, and incineration power plants. Reducing CO2 with power-to-gas technology is thought to be an environmentally friendly approach. A novel fuzzy-random robust flexible programming approach based on Me measure is proposed, which overcomes the limitations of addressing the uncertainty of the parameters. Next, in order to solve the suggested multi-objective model, a novel strategy known as utility function based multi-choice conic goal programming is presented. A case study explores the sustainable challenges of a closed-loop renewable energy supply network in India’s renewable energy sector. The experimental results indicate that 9 candidate locations are selected for solar wafer production facilities, while 10, 9, and 15 locations are chosen for solar cell production, module manufacturing, and solar power plants, respectively. A sensitivity analysis reveals that the proportion of air pollution limitations possessively rises from 100% to 80% corresponding to the aggregate cost increases from INR 8021452 to INR 8056542.

Energy, exergy and economic analysis of a poly-generation system combining sludge pyrolysis and medical waste plasma gasification

To optimize the processes of treating medical waste and pyrolyzing sludge, we propose a new integrated system that combines plasma gasification for medical waste treatment, combined cycle power generation, and sludge pyrolysis. The medical waste is first incinerated, and then the synthesis gas from plasma gasification powers a gas turbine to generate electricity in this integrated system. The gas turbine's exhaust gas heats steam and feedwater from the HRSG to achieve a combined gas-steam cycle. Simultaneously, turbine exhaust steam energizes sludge pyrolysis, allowing for efficient conversion of medical waste into electricity in an eco-friendly manner. A hybrid design study was conducted using different methods, including energy, exergy, and economic analysis. The study revealed that the medical waste-to-energy system integration has the potential to attain 66.31% energy efficiency and 66.70% exergy efficiency. Moreover, the medical waste-electricity project has a dynamic payback period of 2.46 years and a relative net present value of 38,949.91k$. These outcomes suggest that this innovative concept is practical, advantageous, and has excellent potential for further development in the field of waste-to-energy conversion.

Feasibility of coupling hydrogen and methane production in WWTP: Simulation of sludge and food wastes co-digestion

Wastewater treatment plants are essential in improving life quality by degrading organic matter, reducing contamination, and therefore greatly impacting human activities. The role of these critical treatment units can be further promoted by integrating new biological processes that currently are still under experimental scale. The co-digestion of sewage sludge and food waste has been proposed as an efficient way to increase plant treatment capacity and energy recovery. The assessment of hydrogen production along with food waste co-digestion is carried out in the present manuscript. Assessing several parameters is necessary to implement a new biological process in an operating plant, and quantifying its effects on the plant's overall performance is crucial. The implications associated with the extra equipment needed to handle additional waste material were evaluated. Results indicated that a conventional unit may treat a 10 % addition of food waste (expressed as VS) without experiencing severe modifications in process parameters, thus obtaining 16 % extra energy. However, the increase in food waste by over 10 % translates into substantial plant modifications requiring the installation of digesters with higher volumes and handling an additional amount of sludge. Another relevant factor is the lower energetic content of biogas when mixed with hydrogen. The increase in food waste until 50 % VS in the mixture reduced the biogas lower heating value to 15.5 MJ/m3. Future research will deal with an economic analysis of the approach and the effect on engine performance when dealing with a fuel mixture with different combustion properties.

Waste biomass-derived biochar in adsorption-photocatalytic conversion of CO2 for sustainable energy and environment: Evaluation, mechanism, and life cycle assessment

Biochar is an environmentally friendly material with great potential for carbon capture and storage. As the first of its kind, waste biomass-derived biochar was utilized to convert CO2 into fuel in solar. Herein, among four representatives herbaceous, woody, sludge, and manure wastes, the pine sawdust-derived biochar produced the highest CO assisted by higher CO2 adsorption, more than 10 times higher than that of graphene and activated carbon. The function groups of carbonyl and carboxyl on biochar controlled the CO2 capture and solar conversion by decreasing adsorption and activation energies of CO2 molecules. The biochar performed even better for 15% CO2/N2 atmosphere, a typical CO2 concentration in the flue gas, demonstrating its promising potential in waste gas resource utilization. The life-cycle assessment indicates that feedstock with more cellulose and lignin provide better environmental and economic benefits. The work highlights a sustainability pathway for waste biomass-derived biochar in CO2-to-fuel under ambient conditions.

Recycle of soda waste sludge as the limestone material for Portland cement: Chemical composition, physical properties and hydration mechanism

Soda waste sludge (SWS) was discharged from the ammonia-soda process for producing sodium carbonate. It is out of effective treatment method but primarily composed of CaCO3. Limestone material is the necessary raw material for the Portland cement production, accounting for more than 80 wt%. Thus, a Portland cement in this study was produced from the SWS with different Cl- content as the substitute for limestone, and its chemical composition, physical properties, and hydration mechanism was investigated. Results demonstrated that when the Cl- in SWS was reduced to 0.26 wt% through water scrubbing, the chlorine-bearing species such as Ca10Mg0.8[(SiO4)3.4(AlO4)0.6O2Cl], C11A7·CaCl2, and Ca3(SiO4)Cl2 in cement clinkers and the 3CaO·Al2O3·CaCl2·10 H2O and Ca10(SiO4)3(SO4)3Cl2 in its hydration products vanished. And the Portland cement produced from 25.64 wt% SWS meets standard requirements for 52.5-grade cement on the flexural and compressive strengths. Its permeability coefficient was increased from 186.27 ×10−13 m/s to 8.65×10−13 m/s, and the mass loss and compressive strength loss were decreased to 6.53% and 7.33%. Also, the mineral phase composition of cement clinker were the 3CaO·SiO2, 2CaO·SiO2, 3CaO·Al2O3, and 4CaO·Al2O3·Fe2O3, the hydration products were the CSH gels, Ca(OH)2, Al(OH)3, and 3CaO·Al2O3·3CaSO4·32 H2O. This work realizes the application of SWS as the substitute for limestone, which is beneficial to the resource treatment of SWS and the reduction of limestone mining.

Thermogravimetric analysis of co-combustion characteristics of sewage sludge and bamboo scraps combined with artificial neural networks

The increasing amount of sludge resources has brought great challenges to the ecological environment and sustainable development. Co-combustion of low calorific value sewage sludge and biosolid waste has become a new and effective way to treat sludge. The co-combustion characteristics of sewage sludge and bamboo scraps in air were studied by thermogravimetric mass spectrometry and artificial neural network. The thermogravimetric analysis of combustion at three different heating rates was performed with five different mixing ratios. Through comprehensive combustion index and cooperative analysis, it is concluded that the co-burning effect and cooperative effect of sludge and bamboo are better. Flynn-Wall-Ozawa and Kissinger-Akahira-Sunose were used to calculate the apparent activation energy. The average activation energy of the sludge mixed with 75% bamboo scraps was the lowest (126.3 kJ mol−1) under the co-combustion condition. The ion current of combustion gas products during combustion was studied by mass spectrometry. Co-combustion can increase NOx and reduce SO2, and 75% bamboo slag mixed sludge has the least gas production. Finally, the prediction model of sludge co-combustion is established by artificial neural network, which provides a prospective guidance for the resource utilization of solid waste.

Preparation of high-strength ceramsite from coal gangue and printing and dyeing sludge: Design strategy and modelling mechanism

Disposal and harmless utilization of coal-based solid waste, industrial sludge, and other bulk industrial solid waste is a sustainable and economical approach. In this study, coal gangue and printing and dyeing sludge were recycled to reconstruct high-strength ceramsite using a simple and scalable method. The high silica and alumina contents in coal gangue provided a foundation for ceramsite preparation, and the iron oxide in the printing and dyeing sludge could reduce the sintering temperature. The optimal synthesis conditions were as follows: Coal gangue: printing and dyeing sludge = 40:60; sawdust content of 9mass%; sintering temperature of 1175 °C for 15 min; and preheating temperature of 400 °C for 10 min. The designed ceramsite exhibited high compressive strength of 27.26 MPa, low 1-h water absorption of 1.26%, and bulk and apparent densities of 998 and 1597 kg/m3, respectively; thus, it was categorized as high-strength ceramsite. In determining the modelling mechanism during the sintering process, the silicon and aluminum distributions on the ceramsite surface obtained under the optimal preparation conditions was highly consistent, forming a silicoaluminate that supported the ceramsite strength. Sawdust addition increased the pore structure of the ceramsite. The heavy metals contained in the raw materials were well-immobilized in the ceramsite, indicating that the prepared ceramsites were free from secondary contaminants. Use of bulk solid waste to prepare high-strength ceramsites is a feasible resourceful and harmless utilization method, which is of great significance for bulk solid waste disposal and reuse.

Rapid removal of ofloxacin with peroxymonosulfate activation process mediated by Co3O4/Sludge-derived biochar composite: Unveiling the enhancement of biochar

In this study, sludge-derived biochar loaded Co3O4 composite (Co3O4@SDBC) were successfully synthesized through cobalt impregnation and secondary calcination of sludge-derived biochar precursors. The experimental results demonstrated that the Co3O4@SDBC catalyst performed exceptionally well for peroxymonosulfate (PMS) activation, with a high degradation efficiency (>99 %) of ofloxacin (OFL) within 10 min under the optimal conditions (a catalyst dose of 0.10 g•L−1, a PMS dose of 0.975 mM and an initial pH = 6.4), and showed good adaptability across a broad pH spectrum, under the interference of the anions and humic acid (HA), as well as in various water matrices. The results of quenching experiments revealed that the non-radical pathway (especially 1O2 and electron transfer) was the dominated reactive ingredients in the PMS activation process induced by Co3O4@SDBC. Notably, the online electrochemical tests and density functional theory (DFT) results indicated the presence of biochar carrier not only effectively lowered the escape of Co ions, while enhanced the steadiness of Co3O4@SDBC, but also accelerated the electron transfer, promoted the adsorption and cleavage of PMS, facilitated the redox cycle between Co(II) and Co(III), reduced the reaction energy barriers simultaneously, thereby making it more favourable for the generation of 1O2. Furthermore, the toxicity assessment suggested that the cumulative toxicity of OFL decreased throughout degradation. Overall, this work mechanistically revealed the enhancement of biochar on the Co3O4@SDBC catalyst, offering a viable method to activate PMS for antibiotic removal and achieving a mutually beneficial strategy for sludge waste resource utilization and environmental remediation.

Implementation of solidified carbon dioxide to anaerobic co-digestion of municipal sewage sludge and orange peel waste

The waste production is closely related with human activity. Various approaches have been applied to manage and reduce its increasing volume (Paranjpe et al. 2023). One of the possibilities that comply with the assumptions of circular economy is utilization of wastes in anaerobic digestion (AD) process. This technology is common worldwide and it is recognized as the cost-effective methods of energy generation that also allow for nutrient recovery, as well as effective waste management (Alharbi et al. 2023). The biogas generated within this process is considered as a multifunctional renewable source that might be a promising alternative to the depleting traditional fuels. It finds various applications such as heat and power generation, fuel in automobiles, and substrate in chemical industry (Shitophyta et al. 2022, Pradeshwaran 2024). Typically, biogas contains 50–70% of CH4, 30–50% of CO2, and 1–10% of other trace gases like H2, H2S, CO, N2. Its composition mainly depends on the feedstock characteristics, operational conditions, and adopted technology (Gani et al. 2023, Archana et al. 2024). Considering further application, the priority action should be increasing its volume and methane content. There are several strategies to achieve these goals, including implementing codigestion strategy, adding additional component to the main substrate, introducing trace elements essential in AD, pretreatment strategies, and introducing enzymes and microbial strains to digesters (Zhang et al. 2019). Each method has limits related to the implementation costs, changes in the adopted technology, operator training needs, and additional energy input, which might negatively influence the energy balance of wastewater treatment plants (WWTPs) (Meng et al. 2022). Therefore, recent scientific attention has focused on combining various strategies to achieve intended goals. Moreover, such combinations might allow for an effective utilization of various wastes, the earlier use of which in AD was difficult. Orange waste could be an example of such a substrate. The previous studies indicated that its application in AD resulted in poor process efficiency, mainly due to the presence of limonene, recognized as the main inhibitor of biological activity (Calabro et al. 2020, Bouaita et al. 2022). In this study, the novel concept of implementing solidified carbon dioxide (SCO2) in the anaerobic co-digestion of municipal sewage sludge (SS) and orange peel waste (OPW) has been proposed. This approach may help overcome the disadvantages of the two-component AD of these wastes. Importantly, such studies have not been conducted thus far. However, the recent studies indicated that application of SCO2 to aerobic granular sludge improved biogas and methane yields and also enhanced the kinetics of biogas production (Kazimierowicz et al. 2023 a,b). Importantly, SCO2 might be generated in biogas upgrading technologies (Yousef 2019). Such solution is consistent with the principles of the circular economy and contributes to reducing the carbon footprint of WWTPs.

Investigating the characteristics of biomass wastes via particle feeder in downdraft gasifier

Particle feeding plays a crucial role in the gasifier due to its effects on the efficiency and performance metrics of the thermochemical process. Investigating particle size distribution's impact on downdraft gasification reactor performance, this study delves into the significance of feedstock characteristics (moisture, volatile matter, fixed carbon, and ash contents) during the particle feeding stage. Various biomass wastes (date palm waste, olive pomace and sewage sludge) at diverse compositions and sizes are subjected to empirical determination of mass flow rates (MFR), power ratings, and storage times for each feedstock. The preheating process in the gasifier is considered, employing both an approximation and analytical solution. In addition, the influence of the equivalence ratio (ER) on the syngas yield is analyzed. The collected data reveals that for average particle size of 200 μm, the highest MFR (in g/min) are 0.518 ± 0.033, 7.691 ± 0.415, and 16.111 ± 1.050, for palm wood biomass, olive pomace and sewage sludge, respectively. Smaller particles (80 μm) led to extended storage times. Moreover, the lumped capacitance approximation method consistently underestimates preheating time, with a percentage error of 6.26%–17.08%. Response surface methodology (RSM) optimization analysis provides optimal gasification conditions for palm wood biomass, olive pomace, and sewage sludge with maximum cold gas efficiencies (CGEs) of 58.01%, 63.29%, and 52.27%. The peak conversion was attained at gasification temperatures of 1089.83 °C, 1151.93 °C, and 1102.91 °C for palm wood biomass, olive pomace, and sewage sludge, respectively. In addition, gasification equilibrium model determined optimal gasification temperatures as 1150 °C for palm biomass, 1200 °C for olive pomace, and 1150 °C for sewage sludge with respective syngas efficiencies of 59.62%, 64.13%, and 53.66%. Consequently, the examination of the dosing procedure, preheating dynamics, particle dimensions, ER, storage time, and their combined impacts offer practical insights to effectively control downdraft gasifiers in handling a variety of feedstocks.

An Updated Overview of Magnetic Composites for Water Decontamination.

Water contamination by harmful organic and inorganic compounds seriously burdens human health and aquatic life. A series of conventional water purification methods can be employed, yet they come with certain disadvantages, including resulting sludge or solid waste, incomplete treatment process, and high costs. To overcome these limitations, attention has been drawn to nanotechnology for fabricating better-performing adsorbents for contaminant removal. In particular, magnetic nanostructures hold promise for water decontamination applications, benefiting from easy removal from aqueous solutions. In this respect, numerous researchers worldwide have reported incorporating magnetic particles into many composite materials. Therefore, this review aims to present the newest advancements in the field of magnetic composites for water decontamination, describing the appealing properties of a series of base materials and including the results of the most recent studies. In more detail, carbon-, polymer-, hydrogel-, aerogel-, silica-, clay-, biochar-, metal-organic framework-, and covalent organic framework-based magnetic composites are overviewed, which have displayed promising adsorption capacity for industrial pollutants.

Fe[sbnd]N doped carbon materials from oily sludge as electrocatalysts for alkaline oxygen reduction reaction

Alkaline oxygen reduction reaction (ORR) presents an important role for energy conversion technologies and requires the development of an efficient electrocatalyst. Pt-based catalysts provide suitable activity; however, Pt production accessibility and high costs create hurdles to their commercial implementation. Fe coordinated within N-doped carbon materials (FeNC) are a promising alternative due to their high ORR catalytic activity, although the currently commercially available FeNC materials rely on harsh synthetic protocols which can lead to increased environmental impacts. In this work we target this issue by taking advantage of an oily sludge waste currently generated in refineries to synthesize FeNC materials, thus, avoiding the environmental impact caused by the management of this waste. The solid particles within oily sludge, which present a high concentration of C and Fe, were combined by different nitrogen sources and pyrolyzed at high temperatures.The prepared materials present a hierarchical pore structure with surface areas up to 547 m2 g−1. X-ray photoelectron spectroscopy analysis found that the impregnation of N using phenanthroline promotes the formation of pyridinic-N structures, which enhances the ORR performance compared to melamine doping. Additional doping of Fe with phenanthroline results in an ORR mass activity of 1.23 ± 0.04 A gFeNC−1 at 0.9 VRHE, iR-free in a rotating disc electrode (0.1 M KOH). This catalyst also shows a lower relative loss in activity at 0.9 VRHE after 8000 cycles in O2-saturated conditions compared to a commercial FeNC catalyst, PMF D14401, (−63.5 vs −69 %, respectively), demonstrating promise as a cheap and simple route to FeNC catalysts for alkaline ORR.