Processing Residues Research Articles

Improvement of the technological scheme for processing zinc concentrates by hydrometallurgical method at JSC Almalyk MMC

The extraction of zinc from concentrates is carried out in pyrometallurgical and hydrometallurgical ways. Obtaining pure zinc of the highest grades is possible using the hydrometallurgical method, in which the calcined sulfide concentrate is subjected to sulfuric acid leaching, a solution of zinc sulfate and a recycled product is formed - a solid residue of the cake leaching process. After purification, the zinc sulfate solution is subjected to electrolytic refining, and the cake is processed pyroly or hydrometallurgically. At JSC "Almalyk MMC" in the process of hydrometallurgical processing of zinc concentrates, the resulting zinc cake is processed by the pyrometallurgical method - rolling. The rolling process takes place in two tubular furnaces (rolling furnaces) 50 meters long and 3.5 meters in diameter at a temperature of 1100–12000C, in the presence of a reducing agent, coke breeze and petroleum coke. As a result of the rolling process of zinc cakes, sublimates and a solid technogenic residue, clinker, containing copper, gold, and silver are formed. Clinker is processed at the plant in smelting furnaces to extract precious metals, but it is accumulating more than 450 thousand tons. In connection with this, scientific research is currently underway on the processing of zinc cakes using a hydrometallurgical method to eliminate the expensive rolling process of processing zinc cakes; high-temperature (900 C) sulfuric acid leaching of cakes with a size of 0.074 mm has been developed during leaching for 4-4.5 hours, the extraction of zinc into the solution is 98.5%; copper 92.8%; iron 75.2; cadmium 79.2.

Co-designing sustainable biochar business models with sub-Saharan African communities for inclusive socio-economic transformation

Smallholder farmers in sub-Saharan Africa (SSA) encounter multiple livelihood challenges. Embracing circular bioeconomy principles, particularly considering agricultural and food processing residues, could enable inclusive, locally led, sustainable development pathways within rural communities. Biochar products are one such example of a bio-based material that can be generated using circular principles and deployed for sustainable community development, including among smallholder farmers. This research leverages empirical evidence from four SSA regions to explore the potential of inclusive and sustainable biochar business models, namely: (i) Northern Region, Ghana, (ii) Yamoussoukro, Côte d’Ivoire, (iii) Casamance, Senegal, and (iv) Western Region, Uganda. Co-creation workshops using the Triple-Layered Business Model Canvas framework were carried out in each region with local stakeholders to evaluate the social, ecological, and economic implications of four locally relevant biochar applications: water filtration, biogas purification, soil amendment, and cooking fuel briquettes. Data was analysed at an aggregate level for all regions and applications. The study describes this consolidated biochar business model and examines the implications for SSA communities. The resulting sustainable bio-based business model can guide value chain actors and policymakers in SSA communities towards rural sustainable development with a better understanding of the needs, opportunities, challenges, and impacts of biochar-based value chain development.

Analysis of fruit bars elaborated with flour from the residue of acerola processing

Analysis of fruit bars elaborated with flour from the residue of acerola processing

Ethanol distillation performance test of porang flour processing residue in SME scale distillator

Abstract One of the porang processing steps involves the production of porang flour with glucomannan concentrations that meet market requirements. To increase glucomannan levels, impurities are separated. The common solvent used is ethanol. In the extraction procedure, ethanol is not only used once but reused in another extraction procedure by redistilled to increase the concentration of ethanol. This study’s objective is to determine and analyze the effect of input volume variations (5,7.5 and 10 liters) at heating temperatures (85°C, 90°C, and 95°C) on ethanol product volume and concentration. In the distillation process 5; 7.5 and 10 L, ethanol levels respectively in the range of 58.41-71.87%, 61.81-65.87, and 63.76-65.93%. Based on the analysis, the constant value (k) in the change of ethanol distillation level during the distillation process predicted at 5L volume were 0.0149, 0.0160, and 0.0182, for 7.5L volume were 0.0098, 0.0134, and 0.0153, 0.0071, 0.0083, and 0.0102 minutes−1 at 10 L sample volume for each distillation temperature. The optimal values for a distillation device evaluated on a Small Medium Enterprises (SME) scale by varying the volume and temperature of the substance in the distillation vessel were determined to be 5 liters of volume and 95°C, respectively.

Valorization of broiler edible byproducts: a chicken-liver hydrolysate with hepatoprotection against binge drinking

Over 10,000 metric-ton broiler livers are produced annually in Taiwan. Concerning unpleasant odor and healthy issue, broiler livers are not attractive to consumers. Although the patented chicken-liver hydrolysates (CLHs) through pepsin digestion possess several biofunctionalities, there is no study on hepatoprotection of CLH-based formula capsule (GBHP01) against binge drinking (Whiskey, 50% Alc./Vol.). GBHP01 led to an accelerated blood-alcohol clearance in rats, as evidenced by lowering blood-alcohol increment within 0 to 4 h, increasing blood-alcohol decrement within 4 to 8 h, and smaller blood alcohol concentration areas under the curve (BAC AUC) in the 8-h period (p < 0.05). The ameliorative effects of GBHP01 against binge drinking in rats over 6 wk were attributed to accelerated alcohol metabolism by further increasing alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH) activities while downregulating cytochrome P450 2E1 (CYP2E1) protein expression, elevating antioxidant capacity, decreasing zonula occludens-1 (ZO-1) protein decrement and serum endotoxin, and reducing inflammation related protein levels, that is, toll-like receptor 4 (TLR4) and mitogen-activated protein kinase (MAPK), and proinflammatory cytokines. The development of CLH supplements could not only enhance the added value of broiler livers through nutraceutical development but also offer a strategy to maximize the utilization of poultry processing residues, as shown in this study.

Preparation and application of alkali-activated cementitious materials in solidification/stabilization of chromite ore processing residue.

Chromite ore processing residue (COPR) is a typical hazardous waste, which contains Cr(vi) and poses a great threat to the ecological environment and human health. In this study, solidification/stabilization (S/S) of COPR was carried out by using blast furnace slag (BFS) and fly ash (FA) to prepare alkali-activated cementitious materials (AACM). The influence of different factors (water glass modulus, liquid-solid ratio, alkali-solid content and curing temperature) on compressive strength was investigated by single-factor experiment. Additionally, solidification effect of AACM was determined according to the compressive strength and the leaching concentration of chromium (Cr(vi) and total Cr). According to the optimal conditions of the single-factor experiment, the highest compressive strength of 147.6 MPa was obtained after using the water glass modulus 1.0, liquid-solid ratio 0.28, alkali-solid content 8%, curing temperature 45 °C. The COPR was solidified in the AACM sample having highest compressive strength. The solidified body still has a good mechanical property (38.2 MPa) with 60% addition COPR. According to leaching tests, the leaching of Cr(vi) and total Cr of solidified body with 50% COPR was far lower than the limit value, which met the purpose of construction and landfill disposal. X-ray diffraction (XRD) analysis, Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) analysis proved that heavy metal chromium was solidified in AACM by physical and chemical means.

Preparation of 4-Amino-3-hydrazino-1,2,4-triazol-5-thiol-Modified Graphene Oxide and Its Greatly Enhanced Selective Adsorption of Gallium in Aqueous Solution.

Efficient recovery of gallium (Ga) from vanadium slag processing residue (VSPR) solution is of great significance for environmental protection and resource utilization, but improving its selective adsorption against the coexisting Sc3+ and In3+ is still challenging. Herein, a novel adsorbent consisting of 4-amino-3-hydrazino-1,2,4-triazol-5-thiol (AHTZT)-modified graphene oxide (GO-AHTZT) was successfully synthesized that exhibits a higher adsorption selectivity for Ga3+ in VSPR solution with coexisting Sc3+ and In3+. Under optimal conditions, the adsorption capacity of GO-AHTZT for Ga3+ can reach 23.92 mg g-1, which is 4.9 and 12.6 times higher than that for Sc3+ (4.87 mg g-1) and In3+ (1.90 mg g-1) adsorption, indicating the excellent anti-interference ability of GO-AHTZT against Sc3+ and In3+. The process and mechanism of Ga3+ adsorption onto GO-AHTZT was also studied and discussed in detail. By measuring the adsorption process and by characterizing the adsorbent before and after adsorption, we demonstrate that the selective interaction between the Ga3+- and N-containing groups in AHTZT is the main reason for the improved adsorption selectivity. This work opens up an avenue for the design and synthesis of highly selective adsorbents for Ga3+ in complex VSPR solutions.

Supercritical Carbon Dioxide Extraction of Coumarins from the Aerial Parts of Pterocaulon polystachyum.

Pterocaulon polystachyum is a species of pharmacological interest for providing volatile and non-volatile extracts with antifungal and amebicidal properties. The biological activities of non-volatile extracts may be related to the presence of coumarins, a promising group of secondary metabolites. In the present study, leaves and inflorescences previously used for the extraction of essential oils instead of being disposed of were subjected to extraction with supercritical CO2 after pretreatment with microwaves. An experimental design was followed to seek the best extraction condition with the objective function being the maximum total extract. Pressure and temperature were statistically significant factors, and the optimal extraction condition was 240 bar, 60 °C, and pretreatment at 30 °C. The applied mathematical models showed good adherence to the experimental data. The extracts obtained by supercritical CO2 were analyzed and the presence of coumarins was confirmed. The extract investigated for cytotoxicity against bladder tumor cells (T24) exhibited significant reduction in cell viability at concentrations between 6 and 12 μg/mL. The introduction of green technology, supercritical extraction, in the exploration of P. polystachyum as a source of coumarins represents a paradigm shift with regard to previous studies carried out with this species, which used organic solvents. Furthermore, the concept of circular bioeconomy was applied, i.e., the raw material used was the residue of a steam-distillation process. Therefore, the approach used here is in line with the sustainable exploitation of native plants to obtain extracts rich in coumarins with cytotoxic potential against cancer cells.

Use of recycled construction and demolition waste as substrate in constructed wetlands for the wastewater treatment of cheese production

Recycled building debris has recently emerged as a suitable wetland infill substrate due to its low density, exceptional water absorption capabilities, and high porosity. This study investigated, for the first time, the use of construction demolition wastes (CDW), and rock processing residues (RPR) as substrate materials in vertical-horizontal flow hybrid constructed wetlands for the treatment of cheese production wastewater. Results showed that the use of both CDW as well as RPR, as substrate material, provided an equal or even better quality of treated wastewater compared to the conventional use of gravel as a substrate. High removal efficiencies were recorded for turbidity (CDW: 91–92%, RPR: 97%), solids (CDW: 85–88%, RPR: 96–97%), organic matter (CDW: 79–84%, RPR: 96–98%), and total phosphorus (CDW: 72–76%, RPR: 87%) for both examined recycled materials. During the experiment, different loadings rates (HLR) were tested: 25 mm d−1 and 37.5 mm d−1. Radiological measurements indicate that, their use did not cause toxic effects on the environment, as the amounts of radioactivity found in the effluent of the systems are not significant. Increasing the hydraulic loading rate appeared to have no negative effect on pollutant removal, as the systems and plants were fully acclimated and mature. This approach offers several advantages, including the use of readily available and abundant waste material, potential cost savings, and the environmental benefits of recycling CDW and RPR instead of disposing of them in landfills.

Unveiling dissociation mechanisms and binding patterns in the UHRF1-DPPA3 complex via multi-replica molecular dynamics simulations.

Ubiquitin-like with PHD and RING finger domain containing protein 1 (UHRF1) is responsible for preserving the stability of genomic methylation through the recruitment of DNA methyltransferase 1 (DNMT1). However, the interaction between Developmental pluripotency associated 3 (DPPA3) and the pre-PHD-PHD (PPHD) domain of UHRF1 hinders the nuclear localization of UHRF1. This disruption has implications for potential cancer treatment strategies. Drugs that mimic the binding pattern between DPPA3 and PPHD could offer a promising approach to cancer treatment. Our study reveals that DPPA3 undergoes dissociation from the C-terminal through three different modes of helix unfolding. Furthermore, we have identified key residue pairs involved in this dissociation process and potential drug-targeting residues. These findings offer valuable insights into the dissociation mechanism of DPPA3 from PPHD and have the potential to inform the design of novel drugs targeting UHRF1 for cancer therapy. To comprehend the dissociation process and binding patterns of PPHD-DPPA3, we employed enhanced sampling techniques, including steered molecular dynamics (SMD) and conventional molecular dynamics (cMD). Additionally, we utilized self-organizing maps (SOM) and time-resolved force distribution analysis (TRFDA) methodologies. The Gromacs software was used for performing molecular dynamics simulations, and the AMBER FF14SB force field was applied to the protein.

Exploring the potential of nitrophosphogypsum and calcined water-treatment plant sludges in mortar mixtures: A study on workability and strength

Mortar mixtures that consider alternative mineral admixtures are of constant research interest to reduce ordinary Portland cement (OPC) content thereby lowering final cost and carbon footprint. An additional concern is the proper management of industrial process residues that could be used in mortar mixes to avoid their disposal in landfills or water bodies. This work investigated the potential of using calcined water treatment plant sludge (CWTPS) and nitrophosphogypsum (NPG) - a byproduct of the fertilizer industry - as partial replacements of OPC in mortar mixtures. For this purpose, this research evaluates the crystallographic, chemical, and physical properties of NPG and CWTPS through X-ray diffraction (XRD), X-ray fluorescence (XRF), and Scanning Electron Microscope (SEM). XRF and XRD findings strongly suggests that CWTPS qualifies as supplementary cementitious materials, due to its high content of silicon and aluminum oxides in a non-crystalline state. On the other hand, NPG could be used as a mineral admixture. The design of mixtures was based on the workability of 85% flow. The evaluation of properties encompasses the measurement of density, compressive strength, durability (pH and sulfate environments), and water absorption. The results demonstrate that incorporating of NPG and CWTPS to mortar mixes, each at a 5% inclusion rate (with a total replacement of 10% of OPC), increase compressive strength by up to 6.65% at 90 days compared to the control group in mortar mixes. However, the inclusion of NPG and CWTPS significantly decreases the workability of mortar mixes by up to 51.49%. The utilization of NPG as a partial replacement for OPC increases the water-to-cement ratio proportionally compared to the control sample, which can be explained by the anhydrite content of this byproduct. For its part, replacing 10% of OPC with NPG and CWTPS results in a 1.99% decrease in resistance after 28 days in sulfated environments compared to specimens cured in lime water. This protection of NPG against sulfate attack on mortars is based on the fact that SO3 saturation hinders the phase change from AFt to AFm during curing, as demonstrated by the XRD results. Additionally, the inclusion of NPG in mortar mixes increases capillary water absorption by up to 19.8%, while CWTPS, due to its pozzolanic nature, reduces it by up to 5.75%. Finally, this study explores the potential combined use of NPG and CWTPS in mortar mixes as a partial replacement for cement, presenting a viable and sustainable alternative for these cementitious-based construction materials.

Computer-aided framework for the design of entrainer for palm process residue recovery

Oleochemical industry produced substantial palm process residue during hydrogenation process of fatty acid/methyl ester, containing medium- to long-chain fatty alcohols and alkanes with overlapping boiling points. Recovering fatty alcohols for sale and utilizing alkanes for jet fuel, lubricants, and gasoline is beneficial. However, separating them through conventional distillation (CD) is challenging and expensive due to the difficulty in achieving the necessary temperature differentials for phase changes, especially with high reflux ratio required. To address this challenge, extractive distillation (ED) with an entrainer, designed through computer-aided molecular design (CAMD), was employed. However, implementing ED with a high boiling entrainer is challenging due to the high boiling point of the target components. Therefore, the design of the entrainer focused on the relative volatilities (α) of involved components and associated utility costs. Then, Aspen HYSYS was employed to evaluate the performance of the designed entrainer through product purity and economic analysis. For the separation of C10OH and n-C12, octane and dimethylcyclohexane were generated as entrainers. Dimethylcyclohexane entrainer demonstrated superior separation and generated higher profit than octane entrainer. For the separation of C12OH and n-C14, n-C15 was generated as entrainer to replace the infeasible CD. Therefore, the study concluded that ED with tailored entrainer can effectively replace CD for separating fatty alcohols from alkanes, demonstrating significant industrial feasibility.

PELLET PRODUCTION MACHINE DESIGN USING THE AXIOMATIC HOUSE OF QUALITY (AHOQ) METHOD AT NABOLAK FISHERY

In fish farming, the most significant operational cost is the cost of feed or pellets. Nabolak Fisheries is one of the fish farms in Toba Regency. Nabolak Fisheries can process fish harvests directly into packaged derivative products such as fish meat processed into nuggets, fish bones processed into crackers, and dregs from processing residues used as catfish feed. Nabolak fisheries have the potential to produce fish pellets to reduce operational costs and increase revenue. With their own pellet production machine, fish farmers in the Nabolak Fishery can produce their feed and add derivative products. The design of pellet production machines that are effective, efficient, and follow the needs of fish farmers in order to increase farmer productivity. The Axiomatic House of Quality (AHOQ) method is an effective method for solving pellet machine design problems. This method determines what machine specifications are needed by involving customer requirements, functional requirements, and other elements. After obtaining the design and specifications, modeling was carried out using Solidwork software. Solidwork will feature a three-dimensional design. The three-dimensional design produced by SolidWorks is then given to the blacksmith to make the pellet production machine.

Pre-Treatment of Spent Coffee Grounds Using Hydrodynamic Cavitation

Spent coffee grounds (SCGs) constitute the main solid residue of the coffee brewing process. SCGs are generated in significant amounts daily, worldwide. The effective management of this waste through biological processes is still an unresolved problem. In this study, the application of hydrodynamic cavitation (HC) as a pre-treatment method for improving the biodegradability of SCGs suspended in municipal wastewater was proposed. An orifice plate with a conical concentric hole having inlet/outlet diameter of 3/10 mm was applied as the cavitation inducer. Three inlet pressures were chosen: 3, 5 and 7 bar. The effects in time intervals of 0, 5, 10, 20, 30 and 45 min were evaluated. The application of HC led to enhanced biodegradability for each case. The results of multi-criteria decision indicated that the most efficient combination in terms of biodegradability and energy usage was obtained at the pressure of 5 bar and duration of 20 or 30 min, depending on the adopted weights. The improvements of DOC/TOC (dissolved organic carbon/total organic carbon) ratio were 57% and 71%, as compared to the untreated samples. The release of caffeine was found at pressures of 5 and 7 bar. However, at 5 bar, this effect was noticed for the longest times, 30 and 45 min, respectively.

Enhancing Cutin Extraction Efficiency from Industrially Derived Tomato Processing Residues by High-Pressure Homogenization.

This study primarily aimed to enhance the extraction of cutin from industrial tomato peel residues. Initially, the conventional extraction process was optimized using response surface methodology (RSM). Subsequently, high-pressure homogenization (HPH) was introduced to improve extraction efficiency and sustainability. The optimization process focused on determining the optimal conditions for conventional extraction via chemical hydrolysis, including temperature (100-130 °C), time (15-120 min), and NaOH concentration (1-3%). The optimized conditions, determined as 130 °C, 120 min, and 3% NaOH solution, yielded a maximum cutin extraction of 32.5%. Furthermore, the results indicated that applying HPH pre-treatment to tomato peels before alkaline hydrolysis significantly increased the cutin extraction yield, reaching 46.1%. This represents an approximately 42% increase compared to the conventional process. Importantly, HPH pre-treatment enabled cutin extraction under milder conditions using a 2% NaOH solution, reducing NaOH usage by 33%, while still achieving a substantial cutin yield of 45.6%. FT-IR analysis confirmed that cutin obtained via both conventional and HPH-assisted extraction exhibited similar chemical structures, indicating that the main chemical groups and structure of cutin remained unaltered by HPH treatment. Furthermore, cutin extracts from both conventional and HPH-assisted extraction demonstrated thermal stability up to approximately 200 °C, with less than 5% weight loss according to TGA analysis. These findings underscore the potential of HPH technology to significantly enhance cutin extraction yield from tomato peel residues while utilizing milder chemical hydrolysis conditions, thereby promoting a more sustainable and efficient cutin extraction process.

Grain by-products and Saccharomyces cerevisiae application in paper packaging material: impact on physical–mechanical and barrier properties

AbstractRenewable materials and material circularity are key priorities for the coming decades. While paper is the most utilized material in the packaging sector, its applications in food packaging are limited due to low barrier properties. Coating it with petroleum-based polymer barrier coatings renders it unrecyclable both mechanically and biologically. Bio-coated paper packaging, made from agricultural waste or by-products, presents environmentally favorable solutions that can benefit the biological cycle of the circular economy. The main objective of this study is to assess the applicability of grain and beer production by-products in wood pulp food packaging materials. It examines the effects of different grain by-products (industrial wheat grain processing residues and wheat bran) particles and concentrations (15 wt% and 40 wt%), as well as the impact of brewer’s yeast (Saccharomyces cerevisiae) at a concentration of 10 wt%, on the physical–mechanical and barrier properties of Northern bleached softwood kraft (NBSK) and chemithermomechanical (CTMP) pulps. Material composites were fabricated using a standard sheet forming method. Physical–mechanical properties were analyzed through tensile strength, strain at break, tear resistance, and bending stiffness tests. Barrier-related properties were analyzed through roughness, air permeance, and water contact angle tests. Results revealed that the vast majority of physical–mechanical properties decreased with the increase of both types of grain production fillers. Industrial wheat grain processing residues had a lower impact on physical–mechanical properties than wheat bran filler. A higher percentage of property decrease was absorbed in NBSK pulp than in CTMP. Roughness of CTMP can be improved by adding both industrial wheat grain processing residues and wheat bran. Wheat bran particles can increase hydrophobicity. CTMP pulp strength properties can be increased with the addition of yeast; however, the yeast additive’s effect on air permeance demonstrated a negative impact. In the case of NBSK pulp, which has higher primary strength properties, the addition of yeast does not make any significant changes. The conducted experiments demonstrated that, overall, the addition of these fillers resulted in a decline in physical–mechanical properties such as tensile strength, strain at break, tear resistance, and bending stiffness. This decline was more pronounced with higher concentrations of fillers. In the case of CTMP pulp, both types of fillers exhibited similar trends in affecting properties, whereas for NBSK pulp, wheat bran had a more significant impact compared to wheat grain processing residues. The addition of yeast generally led to a reduction in physical–mechanical properties, particularly in tensile strength and tear resistance. However, samples containing yeast displayed increased flexibility compared to controls. The influence on barrier properties varied: while yeast increased air permeability, it also enhanced surface hydrophobicity, thereby reducing the paper’s receptivity to liquids.

Controlled preparation of bamboo charcoal/BiOCl with efficient visible-light-driven photocatalytic activity for organic pollutant degradation using the residues of bamboo processing

In this research, bamboo charcoal (BC)/BiOCl composites were successfully prepared by a simple hydrothermal method, where the BC was derived from the residues of bamboo processing. The BC/BiOCl composites displayed nanosheet structures with tight combination between bamboo charcoal and BiOCl. The oxygen vacancies (OVs) concentration and photoelectric properties of BC/BiOCl composites were boosted with the doped bamboo charcoal. The photocatalytic performance of the composites was evaluated by the degradation of RhB and TCH. Meanwhile, the possible intermediates, degradation pathways and toxicity of the pollutants in the photocatalytic process were elucidated. When the additive dosage of BC and hydrothermal temperature were 5% and 140°C, the 5BC-140 has highest photocatalytic efficiency under visible light irradiation, and the degradation rates of RhB and TCH over the 5BC-140 composite were 97.9% and 69% at 36 min and 120 min, with the kinetic constants of 6.2 times and 2.0 times as high as those of pure BiOCl, respectively. The establishment of Bi-O-C bonds in the BC/BiOCl played a pivotal role in constructing atomic-level interfacial channels to boost the charge carriers’ separation. The enhanced photocatalytic activity was originated from the robust interaction between bamboo charcoal and BiOCl, promoting the rapid transfer of electrons and suppressing the combination of photogenerated electron-hole pairs through the increased oxygen vacancies. In addition, incubation experiments on green beans demonstrated the nontoxicity of contaminant solution degraded by the BC/BiOCl composites.

Green Chemistry on the Ores Leaching Processes Using Organic Acids: A Qualitative Pedagogical Content Analysis Study

Ores leaching projects aimed to recover toxic and valuable metals from industrial residues. Organic acids like acetic acid and methanesulfonic acid were chosen as leaching agents because they have high selectivity on low concentrations of metals and low toxicity. This study aimed to obtain scientists’ conceptions of ores leaching using organic acids presented in concept maps and Teaching Learning Sequence (TLS). The method used in this study was qualitative content analysis consisting of literature collection, descriptive analysis, category selection, and material evaluation from textbooks, review articles and research articles. The result of this study was in the form of a concept map, and TLS illustrate five sequences of learning materials consisting of mineral products in Indonesia, valorization of industrial process residue with green chemistry-oriented, industrial process residue treatment steps, organic acid properties, and examples of the ores leaching process. The leaching process of ores using organic acids in learning is contextual learning that integrates the concepts of acids and bases, redox reactions, and the principles of solubility learned by high school students. This process also applies the principles of green chemistry, preventing waste in the process and using safe solvents. The results of the concept map and Teaching Learning Sequence (TLS) showed the application of green chemistry in learning, which is expected to be used as a design for teaching materials and didactic designs that can support education for sustainable development. Keywords: Green Chemistry, Organic Acids, Pedagogical Content Analysis

Spark plasma sintering of SiC-based bulk materials from carbonaceous residue of rice husk thermal processing

Relevance. The search for a useful application of carbonaceous residues of rice husks thermal processing. These residues due to high silicon content in the inorganic part can potentially be used to produce silicon carbide – an important functional material for various fields of science and technology. Useful utilization of this waste will allow not only solving the environmental problem associated with their inefficient application and formal disposal, but also obtaining value-added products in the form of SiC-based ceramics. Aim. To obtain SiC-based bulk products from carbonaceous residues of rice husk thermal processing by spark plasma sintering with a minimum number of additional stages of feedstock processing. Objects. SiC-based bulk products obtained using carbonaceous residues of rice husk thermal processing. The samples were obtained by spark plasma sintering at 1800 °C, pressure of 60 MPa and holding time of 10 minutes. Methods. Spark plasma sintering; X-ray diffractometry (X-ray phase analysis); scanning electron microscopy; vacuumless arc discharge synthesis method. Results. The authors have carried out the experimental studies to assess the possibility of applying carbonaceous residue of rice husk thermal processing as a precursor for the synthesis of silicon carbide in bulk (ceramics) and dispersed (powder) forms. A series of experiments on spark plasma sintering of carbonaceous residue from rice husk thermal processing in the initial and milled form, with SiO2 silica sand additives, as well as with the use of silicon carbide powders synthesized from carbonaceous residue by vacuumless arc discharge method were implemented. The latter is performed within a one-stage fast-flowing process in an air environment and does not require the use of a vacuum system. Preliminary results demonstrated the possibility of obtaining bulk products and dispersed powders based on silicon carbide with a content of at least 50 and 60 wt %, respectively, and indicate the prospects of further increasing phase purity by optimizing spark plasma sintering and vacuumless arc discharge synthesis.

Environmental and Economic Life Cycle Assessment of Enzymatic Hydrolysis-Based Fish Protein and Oil Extraction

As global fish consumption rises, a large amount of waste is generated that is generally neglected. Considering the value embedded in these resources, sustainable methods become more important in extracting valuable ingredients from fish processing residues. Enzymatic hydrolysis is a fast and easily reproducible method for recovering protein ingredients and obtaining valuable by-products. To confirm its advantages, an environmental and economic impact assessment is essential. This study overviewed the sustainability and economic viability of extracting protein compounds and oil from Atlantic mackerel processing residues using enzymatic hydrolysis. Life cycle assessment (LCA) and life cycle cost analysis (LCCA) methods were employed. It was found that the climate change impact of the whole process was 0.073 kg CO2-eq per 1 g of fish protein hydrolysate (FPH). As the process produces FPH as the main product and fish oil as the by-product, economic allocation was used to distribute the impacts of FPH and fish oil. The findings of the LCCA showed that producing 1 g of FPH costs EUR 3.68. The contribution analysis indicated the crucial role of electricity and fish in environmental impacts. To ensure the accuracy of the calculation, the results of an LCA study published previously were recalculated. The sensitivity analysis showed that the results were susceptible to the region and source of electricity production. This research provides valuable insights into the sustainability and economic aspects of using enzymatic hydrolysis for extracting protein ingredients and oils from Atlantic mackerel. This can inform future investigations of environmentally friendly and economically viable solutions for extracting fish ingredients.