Waste Components Research Articles

Eco-friendly approach for enhancing the floatability of non-metallic components in waste printed circuit boards: Adding gutter oil during dry grinding

Waste printed circuit boards (WPCBs) are an attractive secondary resource that is challenging to dispose of due to its complexity. Reverse flotation is an effective method to remove non-metallic particles (NMPs) to obtain metals from WPCBs. Nevertheless, the removal of NMPs is usually inadequate in the present flotation practice. Thus, to provide a clean approach to improve the removal efficiency of NMPs, the method of adding gutter oil during dry grinding process was adopted to enhance the hydrophobic sites on the surface of NMPs to improve the floatability. The surface morphology of NMPs was analyzed by SEM, the results show that the rough morphology inhibited the adhesion of bubbles, while water occupied the cracks and pores, making it challenging for collector adsorption, which result in unstable particle-bubble adhesion. The results of FTIR indicate that both NMPs and gutter oil have –CH3, –CH2, -C = O, -C-O functional groups, which promotes the adsorption of gutter oil on the surface of NMPs. The contact angle (CA) results show that the adsorption of gutter oil on the particle surface is conducive to the formation of enhanced CA. Furthermore, the flotation enhancement effect was verified by flotation kinetic experiments. The accumulated floats yield of NMPs conditioned by gutter oil during grinding is increased from 67.05% (NMPs without conditioning) to 95.02%, and the resin recovery is increased by 31.10%. It is demonstrated that dry grinding with gutter oil can strengthen the floatability of NMPs, which provides a potential approach to increase the flotation efficiency of WPCBs.

Isolation and Biological Evaluation of Alfa-Mangostin as Potential Therapeutic Agents against Liver Fibrosis.

The increased proliferation and activation of hepatic stellate cells (HSCs) are associated with liver fibrosis development. To date, there are no FDA-approved drugs for the treatment of liver cirrhosis. Augmentation of HSCs apoptosis is one of the resolutions for liver fibrosis. In this study, we extracted α-mangostin (1,3,6-trihydroxy-7-methoxy-2,8-bis(3-methyl-2-butenyl)-9H-xanthen-9-one) from the fruit waste components of mangosteen pericarp. The isolated α-mangostin structure was determined and characterized with nuclear magnetic resonance (NMR) and high-resolution mass spectrometry (HRMS) and compared with those known compounds. The intracellular signaling pathway activities of α-mangostin on Transforming growth factors-beta 1 (TGF-β1) or Platelet-derived growth factor subunit B (PDGF-BB) induced HSCs activation and were analyzed via Western blot and Real-time Quantitative Polymerase Chain Reaction (Q-PCR). α-Mangostin-induced mitochondrial dysfunction and apoptosis in HSCs were measured by seahorse assay and caspase-dependent cleavage. The in vivo anti-fibrotic effect of α-mangostin was assessed by carbon tetrachloride (CCl4) treatment mouse model. The data showed that α-mangostin treatment inhibited TGF-β1-induced Smad2/3 phosphorylation and alpha-smooth muscle actin (α-SMA) expression in HSCs in a dose-dependent manner. Regarding the PDGF-BB-induced HSCs proliferation signaling pathways, α-mangostin pretreatment suppressed the phosphorylation of extracellular-signal-regulated kinase (ERK) and p38. The activation of caspase-dependent apoptosis and dysfunction of mitochondrial respiration (such as oxygen consumption rate, ATP production, and maximal respiratory capacity) were observed in α-mangostin-treated HSCs. The CCl4-induced liver fibrosis mouse model showed that the administration of α-mangostin significantly decreased the expression of the fibrosis markers (α-SMA, collagen-a2 (col1a2), desmin and matrix metalloproteinase-2 (MMP-2)) as well as attenuated hepatic collagen deposition and liver damage. In conclusion, this study demonstrates that α-mangostin attenuates the progression of liver fibrosis through inhibiting the proliferation of HSCs and triggering apoptosis signals. Thus, α-mangostin may be used as a potential novel therapeutic agent against liver fibrosis.

Emission characteristics of typical gas pollutants during oxygen-enriched waste incineration process

Oxygen-enriched waste incineration can improve incineration efficiency and reduce pollutant generation, while greenhouse gases and pollutant emission characteristics of different wastes are still unclear. In this study, pollutant emission characteristics of actual municipal solid waste (MSW) and typical components at different oxygen concentrations and moisture content were investigated to reveal the pollutant generation mechanism. The results illustrated that when oxygen concentrations increased from 21% to 30%, CO, CH4 and HCN emissions decreased by 95%, 95.5% and 96.5%, respectively. NO emissions increased by 75% due to the promotion of oxygen on fuel NO and rapid NO. The slight increase in SO2 (from 25.8% to 26.87%) was due to the promotion of oxygen on organic S and the reaction between SO42− and HCl. The decrease in HCl emissions (from 78.42% to 76.85%) was caused by the increasing deacon reaction. Besides, with increasing moisture content, CO, CH4 and HCN generation decreased first because of the CO oxidation and CH4 reforming reaction, and then increased due to the water–gas reaction between fixed carbon and water. Furthermore, the moisture content contained (66%) would promote NO and HCl generation by 35.7% and 9.1% through fuel N oxidation by OH radicals and hydrolysis of chlorine salt at high temperatures. The increased oxygen concentration would inhibit the moisture influence and improve applicability for different MSW. In addition, 25% oxygen-enriched incineration was selected as the most suitable parameter for improving combustion efficiency and reducing pollutant emissions of MSW with high moisture content.

Adsorption behavior of platinum-group metals and Co-existing metal ions from simulated high-level liquid waste using HONTA and Crea impregnated adsorbent

The volume and toxicity of radioactive waste can be decreased by separating the components of high-level liquid waste according to their properties. An impregnated silica-based adsorbent was prepared in this study by combining N,N,N′,N′,N″,N″-hexa-n-octylnitrilotriacetamide (HONTA) extractant, N′,N′-di-n-hexyl-thiodiglycolamide (Crea) extractant, and macroporous silica polymer composite particles (SiO2–P). The performance of platinum-group metals adsorption and separation on prepared (HONTA + Crea)/SiO2–P adsorbent was then assessed together with that of co-existing metal ions by batch-adsorption and chromatographic separation studies. From the batch-adsorption experiment results, (HONTA + Crea)/SiO2–P adsorbent showed high adsorption performance of Pd(II) owing to an affinity between Pd(II) and Crea extractant based on the Hard and Soft Acids and Bases theory. Additionally, significant adsorption performance was observed toward Zr(IV) and Mo(VI). Compared with studies using the Crea extractant, the high adsorption performance of Zr(IV) and Mo(VI) is attributed to the HONTA extractant. As revealed from the chromatographic experiment results, most of Pd(II) was recovered from the feed solution using 0.2 M thiourea in 0.1 M HNO3. Additionally, the possibility of recovery of Zr(IV), Mo(VI), and Re(VII) was observed using the (HONTA + Crea)/SiO2–P adsorbent.

Assessment of The Geotechnical Properties of Municipal Solid Waste and Its Effect on The Surrounding Soil: A Review

Due to rapid growing of population and active lifestyle, massive amounts of municipal solid waste (MSW) are produced worldwide. The MSW can harm the environment and threaten the land if the dumping sites are not managed scientifically. The geotechnical properties of MSW are the key parameters required in the landfill operations and waste management facilities. Hence, presence of the geotechnical properties data of the waste can assist engineers in selecting possible solutions for extension of the landfill and obtaining prior background data for the evaluation and design of landfills. MSW disposal changes the geotechnical properties of soil. Also, alterations in the geotechnical properties of soils may contribute to the physical and physico-chemical interactions between soil and contaminants of the dumping sites. As leachate, which is generated by the waste, penetrates into the soil, it moves pollutants into the soil and influences the strength and stability of the soil. The main objective of this research is to summarize the most recent literature of the physical and mechanical properties of MSW, and their influence on the geotechnical properties of soil. The findings of numerous investigations on the physical and mechanical characteristics of MSW and soil influenced by MSW are presented and discussed. Depending on the reviewed research studies, it can be observed that the engineering characteristics of MSW are complicated and varied for various reasons. The waste components and degradation process can cause an increase in moisture content and unit weight, and a decrease in organic content, hydraulic conductivity and compressibility of MSW. Additionally, MSW sites significantly impact the physical and mechanical characteristics of underlain and surrounding soil and deteriorate the soil quality. Further, it was noticed that the influence of dumping on soil is reduced with depth due to less interaction between the soil and waste

Leftovers lovers vs. haters: A latent class analysis on dinner leftover management behaviours

Leftovers are particularly at risk of being discarded, and therefore a main component of household food waste. This study provides insights into sources of heterogeneity in leftover management behaviours, with a particular focus on the use of meal kits providing matched portion and ingredient sizes, and identifies consumer segments via a latent class analysis. We investigate whether belonging to a segment with positive attitudes toward leftovers, and engagement in conscious leftover management behaviours decreases the amounts of dinner leftovers and food waste. Besides, we demonstrate that several food waste antecedents, emotions, personal norms, intention and dinner procurement routines elicit leftover management segment membership. In addition to examining such individual differences, we also investigate the role of meal-level determinants, in particular, whether meal kits heterogeneously affect dinner leftovers depending on the consumer's leftover management segment.Data was collected from 868 households from six countries, using an online survey and diaries. Results of the latent class analysis point towards five consumer segments. We found differences in dinner leftovers amount across classes and detected heterogeneous effects of meal kits. That is, meal kits were able to diminish leftovers in two segments, but not in the other segments. These results provide novel insights into consumer heterogeneity regarding the occurrence, antecedents, and potential solutions of leftovers and resulting household food waste. Implications for both theory and policy are discussed.

Resource recovery potential of Kumasi landfill waste

Landfill mining is an innovative way to minimize environmental pollution, secure land and airspace, and recover secondary raw materials from landfills. The study examined the characteristics of landfilled waste at the Kumasi landfill and its potential for resource recovery. Samples were collected based on the deposition age and characterized in the laboratory. Characteristics determined were composition, volatile solids, moisture content, and heavy metal concentrations. The results indicated that the most significant recoverable resources were Decomposed Organic Materials (organic waste mixed with sand and papers) and combustibles (plastics, wood, and textile), constituting 44 % and 36 % by weight, respectively. The composition of the landfill waste was found to be influenced by the components of waste initially disposed at the landfill and its subsequent age of deposition. The metal content concentration was, however, independent of the age of deposition. The results indicate that a landfill mining project at the Kumasi landfill will make available about 89 % of the landfill volume and airspace for reuse. However, the DOMs recovered may not be suitable for application as compost on agricultural soils due to the high zinc concentrations unless applied to zinc-deficient soils. It may, however, be used as construction material in earthworks and as cover materials at landfill sites. The combustible component can be combusted to generate heat for producing hot water for hospitals, hotels, and old age care facilities.

Components of citrus pulp waste (eureka lemon and clementine) and yellow maize commonly used as livestock feed by south African farmers

Citrus is one of the most extensively grown fruits in several parts of the world. Therefore, its inustrial processing produces large amounts of pulp waste. This study was aimed at assessing the nutritive as well as mineral components of citrus pulp waste of Eureka lemon and Clementine from two Citrus farms while drawing potential comparisons with yellow maize for livestock feed. Proximate analyses were done using approved/standard analytical methods of the Association of Official Analytical Chemists (AOAC), while the mineral constituents were analysed using an inductively coupled plasma optical emission spectroscopy (ICP-OES). Proximate evaluation revealed that Eureka lemon and Clementine pulp waste contained comparable amounts of fibre and lipid, and significantly higher protein contents than yellow maize. Meanwhile, minerals including Ca, Mg, K, Na, Zn, Cu, Mn and Fe were significantly higher in the citrus lemon pulp waste than in yellow maize. The study therefore points out that the Citrus pulp waste have the potentials to be put to more relevant livestock nutritional use.

Ecological Footprint Assessment of Hospitals in Solan City of Himachal Pradesh

This study was carried out in selected hospitals of Solan Town of Himachal Pradesh to assess the ecological footprint which appraised the load of different components namely electricity, water, food, material, transportation and biomedical waste, imposed by the hospitals on the natural environment. The total ecological footprint of all four selected hospitals of Solan town viz., Regional Hospital, Shiva Hospital, City Hospital and Sai Sanjivni Hospital was found to be 1553.75 gha 100.10 gha, 165.44 gha and 185.31 gha respectively during the year 2021. Transportation and material components registered the highest contribution towards the Ecological Footprint (EF) of the Hospitals and the lowest contribution was made by biomedical waste and electricity components. The maximum Ecological Footprint per area (6.02 gha) was exhibited by Sai Sanjivni Hospital and the minimum (0.75 gha) by the Regional Hospital. The sum Ecological Footprint for all the selected Hospitals was 2004.6 gha, whereas the average bio-capacity per capita was 0.0095 gha. It was concluded that the Ecological Footprint of all selected hospitals exceeded bio-capacity, resulting in un-sustainability. The hospitals had extremely poor bio-capacity, making it hard for them to keep up with the expanding footprints.

A Novel Quantitative Analysis Method for Lead Components in Waste Lead Paste

In this study, a method for determining the lead components in waste lead paste was proposed, using simulated and spent lead paste as research objects. To compare the effectiveness of different determining methods, we selected three methods for comparison and investigated the reasons for measurement deviation. The results indicate that the measurement deviation in the current method primarily stems from the following three factors: (1) Pb is soluble in an acetic acid solution under certain conditions; (2) Pb and PbO2 undergo redox reactions; and (3) hydrogen peroxide can undergo redox reactions with Pb. It is feasible to determine the lead content using the kinetic rules of Pb and PbO2 in the acetic acid-hydrogen peroxide system. The method of determination proposed in this paper is as follows. Firstly, lead dioxide is dissolved in hydrogen peroxide under acidic conditions. Subsequently, the concentration of lead dioxide is determined, and the quantity of hydrogen peroxide consumed is recorded. Then, a new sample is taken, and the lead oxide is dissolved in an acetic acid solution. The concentration of lead oxide is determined using the EDTA·2Na titration method. The residue of lead sulfate in the filtrate is dissolved in a sodium chloride solution, and its concentration is determined using the EDTA·2Na titration method. Based on the previously recorded volume of hydrogen peroxide, the remaining lead dioxide in the residue is dissolved in a mixture of acetic acid and hydrogen peroxide. The remaining lead dioxide is then removed from the new sample employing kinetic principles. Finally, the residual metallic lead in the sample is dissolved in a nitric acid solution, and its concentration is determined using the EDTA·2Na titration method.

Treatment of landfill leachate using photocatalytic based advanced oxidation process – a critical review

Landfill leachate is a discrete volumetric component of municipal solid waste; hence, researchers and professionals are more concerned about it because of its obscurity. Innovative treatment and emerging technologies are being scrutinized to address the treatment of landfill leachate challenges. The leading target of this review was to examine the possibility of removing recalcitrant organic pollutants from landfill leachate by photocatalytic–based advanced oxidation processes. A summary of the systematic applicability of conventional treatment for landfill leachate is provided, with a focus on physico-chemical and biological processes. The biological treatment, such as aerobic and anaerobic digestion, is an excellent technique for treating highly concentrated organic pollutants in the wastewater. However, Leachate can scarcely be treated using conventional techniques since it is enriched with refractory organics and inorganic ions. It is clear from the literature review that none of the available combinations of physico-chemical and biological treatments are entirely relevant for the removal of recalcitrant organic pollutants from leachate. Recently, the photo–assisted TiO2/ZnO oxidation has shown an excessively potential and feasible way to treat landfill leachate. TiO2/ZnO photocatalysis is currently developing to treat recalcitrant organic pollutants from landfill leachate. The effect of operating parameters reveals that pH and temperature affect the reaction rate. The addition of oxidant H2O2 to the TiO2/ZnO suspension suggests that TiO2 leads to an increase in the rate of reaction when compared to ZnO. Photocatalytic remediation technique of landfill leachate would support the goal of environmental sustainability by greatly enhancing the effectiveness of treated leachate reutilization. In this review, the selection of the best photocatalytic treatment for leachate based on its systematic relevance and potential conditions, characteristics, cost-effectiveness, essential controlling, discharge limit, long-term environmental effects, and its future study perspectives are emphasized and discussed.

Evaluation and optimization of hydrothermal carbonization condition for hydrochar and methane yield from anaerobic digestion of organic fraction of municipal solid waste (OFMSW)

Effectively converting and utilizing the organic fraction of municipal solid waste is a critical strategy to combat environmental pollution and optimize resource utilization. Responsible handling of waste by-products in an environmentally sustainable manner is essential. The utilization of hydrothermal carbonization and anaerobic digestion are rising as progressive, environmentally sustainable technologies for handling the organic component of municipal solid waste, with the added benefit of energy recuperation. Given distinct experimental objectives, comprehensively investigating the optimal conditions for both hydrothermal carbonization and anaerobic digestion experiments with hydrochar feed poses significant challenges. As a result, this study centers its attention on the hydrochars generated through the hydrothermal carbonization process and their impact on the anaerobic digestion of the organic fraction of municipal solid waste. In the first, the relationship between proximate analysis, ultimate analysis, fuel properties, fiber composition, and methane yield of hydrochars at different conditions (150 ≤ temperature ≤ 230 °C, 20 ≤ retention time ≤ 60 min, and 0.15 ≤ biomass loading ≤ 0.35 g/ml) was evaluated. The content of carbon and hydrogen was increased while the content of oxygen decreased. The hydrothermal carbonization process resulted in an increase in the carbon and hydrogen content, accompanied by a decrease in oxygen content. Moreover, alterations in temperature and retention time during the hydrothermal pretreatment led to variations in the contents of cellulose, hemicellulose, and lignin in the hydrochars. Upon subjecting the hydrochars to anaerobic digestion, the methane yield exhibited a wide range, varying from −51.3 to 61.69% in comparison to the control sample. These outcomes emphasize the significant influence of hydrothermal carbonization conditions on the subsequent anaerobic digestion process, yielding a diverse spectrum of methane production levels. Subsequently, the Response Surface Method, a statistical methodology, was employed to investigate the influence of three parameters. Through this approach, optimal conditions were determined to achieve the maximum hydrochar yield (HC150-20-0.35) at 68.6%, the maximum methane yield (HC168.52-39.47-0.19) at 251.38 ml/g VS, and the simultaneous maximization of hydrochar yield and methane yield (HC159.9-28.75-0.23) at 63.1% and 237.68 ml/g VS, respectively. Finally, the structural and morphological properties of the optimized hydrochars were subjected to thorough analysis.

Plastic debris, persistent organic pollutants and their toxicity impacts in coastal areas in Central Chile

The chemical components of plastic wastes have made their disposal a major economic, social, and environmental problem worldwide. This study evaluated the acute toxicity and genotoxicity of marine plastic debris on the beaches of Concepción Bay, Central Chile, taken during three periods (spring, summer, and winter). An integrated approach was used, including chemical and toxicological data, using the Microtox® test with Vibrio fischeri and SOS chromotest with Escherichia coli and concentrations of polychlorinated biphenyls (PCBs), Organochlorine Pesticides (OCPs) and polybrominated diphenyl ethers (PBDEs). The results presented here exclusively include the novel data obtained from the winter campaign, revealing high concentrations of PBDEs (238 ± 521 ng g−1). In addition, the genotoxicity and acute toxicity tests were sensitive for most of the samples studied. This investigation is the first attempt to analyse the toxicity of plastic debris in coastal areas along the Chilean coast.

Net zero greenhouse emissions and energy recovery from food waste: manifestation from modelling a city-wide food waste management plan

Food waste (FW) being a major solid waste component and of degradable nature is the most challenging to manage and mitigate greenhouse gas emissions (GHEs). Policymakers seek innovative approaches to achieve net zero objectives and recover resources from the FW which requires a comparative and holistic investigation of contemporary treatment methods. This study assessed the lifecycle of six alternative scenarios for reducing net GHEs and energy use potential from FW management in a metropolis, taking Hong Kong as a reference. In both impact categories, the business-as-usual (landfilling) was the worst-case scenario. The combined anaerobic digestion and composting (ADC) technique was ranked best in the global warming impact but was more energy intensive than anaerobic digestion with sludge landfilling (ADL). Incineration ranked second in net GHEs but less favourable for energy recovery from FW alone. The proposed integration of FW and biological wastewater treatment represented an enticing alternative. Integration by co-disposal and treatment with wastewater (CoDT-WW) performed above average in both categories, while anaerobic co-digestion with sewage sludge (AnCoD-SS) ranked fourth. The sensitivity analysis further identified critical parameters inherent to individual scenarios along with biogenic carbon emission and sequestration, revealing their significance on the magnitude of GHEs and scenarios’ ranking. Capacity assessment of the studied treatment facilities showed a FW diversion potential of ∼60% while reducing the net GHEs by ∼70% compared to the base-case, indicating potential of net zero carbon emissions and energy footprint by increasing treatment capacity. From this study, policymakers can gain insights and guidelines for low-carbon urban infrastructure development worldwide.

MoO3 Solubility and Chemical Durability of V2O5-Bearing Borosilicate Glass

In the vitrification of high-level radioactive liquid waste (HLW), the separation of sodium-molybdate melts is a problem because it reduces the chemical durability of the vitrified waste. A glass with both high MoO3 solubility and chemical durability is required for the safe disposal of radioactive waste. In this study, we investigate the effects of vanadium oxide on the phase separation of the molybdenum-rich phase and the water resistance of the resulting glass by phase equilibrium experiments and chemical durability test. Phase equilibrium experiments were performed on SiO2-B2O3-Al2O3-ZnO-CaO-Na2O-LiO2-MoO3 system glasses and on glasses with V2O5 added. The results showed that MoO3 solubility increased when V2O5 was added. The increase in MoO3 solubility in borosilicate melts may be associated with the viscosity-lowering effect of V2O5. Chemical durability tests were performed on borosilicate glass compositions obtained from phase equilibrium experiments. The normalized leaching rates of V2O5-bearing glasses were higher than those of other glasses. This is due to the higher network modifier/network former ratio of the glass tested. The normalized elemental mass loss of glass containing waste components increases with increasing leaching duration. This suggests that the waste component prevents the formation of a gel layer at the reaction front.

Dolomite type nephrite processing wastes and their application

The demand for ornamental stone material has led to an increase in the amount of rock mass being processed. However, the production of lapidary works and jewelry result in a significant amount of waste. This study aims to investigate the material composition and physical and mechanical properties of the solid wastes generated during the processing of dolomite type nephrite in the Vitim region. The accumulation of such waste leads to increased costs of transportation, storage, security, and negative environmental impact. The majority of dolomite type nephrite deposits are located in the Northwest, Northeast, and South of China, in South Korea, Australia, Italy, and Poland, with a large deposit in the Vitim region of Russia. In this study, the waste from the Kavoktinsky deposit, the most productive in Russian, was used. A visual and petrographic examination of nephrite, skarn and amphibolite which are components of the solid waste, was conducted. The macro- and microchemical composition of nephrite of different colors was studied, and X-ray phase analysis was performed. The decorative properties of the waste were determined. A radiation and hygienic certificate was obtained. The waste has a crushability grade of 1200, abrasion grade of I1, and frost resistance of F400. The study has shown that the waste does not contain grains of incompetent rocks, clay, dust, and clay particles. The solid waste form the Vitim nephrite processing is of high quality and meets the requirements of GOST 8267-93, except for an increased content of flagstone (flattened) and large size fragments. It can be used for the production of ordinary, decorative, and mosaic concrete, decorative plates, interior decoration of premises, bathrooms, and saunas, and the manufacture of souvenir products. However, further research is needed to investigate the application of the waste as a raw material for stone casting and a slow-release fertilizer. The utilization of this waste not only solves the problem of waste disposal but also improves economic performance of mineral extraction.

Selection of the final solid waste disposal site in the Bolgatanga municipality of Ghana using analytical hierarchy process (AHP) and multi-criteria evaluation (MCE)

The various components of Municipal Solid Waste (MSW) such as collection, sorting, transportation, and disposal have their peculiarities and challenges. However, final disposal sites, generally referred to as landfill sites, present a complex difficulty. The aggregation of the problems of other components has consequences on the microenvironment, public health, and groundwater. Final disposal of MSW, site selection, and management presents an enormous burden for most Metropolitan, Municipal, and District Assembly (s) in Ghana. The case of Bolgatanga Municipality is similar to many others in the Upper East region in particular and Ghana as a whole. The existing landfill site is improperly sited and poses a great danger to adjoining communities. In this work, we used the Analytical Hierarchy Process (AHP) in a G.I.S. suite and Multi-Criteria Evaluation to assess the current location and select a possible new site within the municipality. The criteria used are generally environmental and socio-economic parameters, including; distance from major roads, rivers, settlements, and the selection of an appropriate slope and soil type that suits the guidelines for the siting of a landfill. The outcome of this multi-criteria assessment is the selection of a new site far from the current disposal site indicating the inappropriate location of the current site. A combination of all weighted criteria through a model builder process produced a suitability index map for candidate landfill sites. The selected site at Sherigu is about 16 km by road from the proposed site, which is much bigger than the threshold of 500 sq. meters. The separation distance and size between the current and the proposed site are indications of how economically and environmentally inappropriate the Sherigu site is and the need for a better site that is better situated for socio-economic and environmental considerations.

Thermal and mechanical properties of a new insulation composite material

Abstract The Taguchi optimization method was used to optimize waste and natural different components such as waste marble dust, expanded perlite, perlite aggregate size, cement, and molten tragacanth in the production of new insulation composite material. Compressive strength, thermal conductivity, abrasion loss, and water adsorption properties of the developed composite material were investigated. Taguchi’s standard L18 array was chosen for optimization of these four components with different levels. Response plots were created using the Taguchi and the optimum test condition was determined. The insulation composite material with the best thermal and mechanical properties was obtained under the condition of waste marble dust (1), expanded perlite (1), perlite aggregate size (1) and molten tragacanth (1). In addition, using the anova (Analysis of Variance), percentage impacts on the mechanical and thermal properties of the test parameters were determined. Statistical values obtained from anova and mathematical models are developed by using multi-linear regression method. It was found that the mathematical model and the experimental results were quite compatible. The optimum test conditions detected were verified by confirmation experiments. Confirmation experiment results were obtained between 99.9 % confidence interval values.

Enhancing PHA production through metal-organic frameworks: Mechanisms involving superproton transport and bacterial metabolic pathways

The effective fermentation of organic waste for polyhydroxyalkanoate (PHA) production is crucial for waste pollution prevention and comprehensive utilization. Glycerol, a common component of organic waste and a by-product of biodiesel production, can serve as a valuable raw material for PHA synthesis. This study explored the potential of metal-organic frameworks (MOFs), specifically MOF-808, to enhance the PHA production by Cupriavidus necator (C. necator) and Bacillus cereus (B. cereus) using glycerol as the substrate. Our results demonstrated that the addition of MOF-808 significantly promoted PHA synthesis without altering the PHA composition. Notably, the proportion of PHA to cell dry weight (CDW) increased significantly (P < 0.05) in both C. necator (from 17.17% to 30.43%) and B. cereus (from 11.30% to 37.93%), with a shortened growth period observed in the latter. The enhanced superproton transport properties of MOF-808 elevated the ATP energy supply level, regulated coenzyme A metabolism, and modulated the PHA synthesis pathway in the bacterial strains. Additionally, MOF-808 improved the utilization of the PHA precursor acetyl-CoA by C. necator, and enhanced the PHA production in B. cereus by facilitating cell growth and PHA synthesis in two distinct stages. Importantly, the recovered MOF-808 structure remained stable, enabling potential recycling. This study provides compelling evidence for the enhancement of PHA production and offers valuable insights into the utilization of organic waste as a valuable resource.

Products and bromine migration characteristics of non-metallic components of waste printed circuit boards pyrolysis in a fluidized bed pyrolyzer

This study investigated non-metallic components (NMCs) of waste printed circuit boards (WPCBs) pyrolysis in a fluidized bed pyrolyzer (FBP). The pyrolysis temperature was set at 350–750 °C. K2CO3, ZnO, CaO and Fe2O3 were added at the temperature of 650 °C to stabilize Br. The characterization of pyrolysis char, pyrolysis oil and pyrolysis gas were analyzed. Migration and transformation of Br in NMCs pyrolysis was investigate. Brominated epoxy resin cracking and Br fixation mechanism were proposed. Pyrolysis oil yield reached the highest at 650 °C. Phenols were the main components of pyrolysis oil, it increased with temperature and reached the highest at 650 °C. The proportion of esters and ketones were 2–4% and 2–3%, respectively. The secondary cracking during pyrolysis correlated the secondary release of CO2, CO, CH4 and H2. Br mainly distributed in pyrolysis oil in the form of HBr and reached the maximum at 550 °C. Organic bromides was mainly bromophenols in pyrolysis oil. Br distributed in pyrolysis char was mainly inorganic bromines in the form of brominated salts. Bromines in pyrolysis gas were mainly CH3Br, C2H5Br, C3H7Br, C3H5Br. K2CO3, CaO effectively promoted Br fixation through neutralization reaction, direct elimination and dissociation adsorption. ZnO, Fe2O3 promoted bromides cracking.