Natural bio-waste-derived 3D N/O self-doped heteroatom honeycomb-like porous carbon with tuned huge surface area for high-performance supercapacitor.

Supercapacitor electrodes (SCs) of carbon-based materials with flexible structures and morphologies have demonstrated excellent electrical conductivity and chemical stability. Herein, a clean and cost-effective method for producing a 3D self-doped honeycomb-like carbonaceous material with KOH activation from bio-waste oyster shells (BWOSs) is described. A remarkable performance was achieved by the excellent hierarchical structured carbon (HSC-750), which has a large surface area and a reasonably high packing density. The enhanced BWOSs-derived HSC-750 shows an ultrahigh specific capacitance of 525 F/g at 0.5 A g-1 in 3 M KOH electrolyte, as well as high specific surface area (2377 m2 g-1), pore volume (1.35 cm3 g-1), nitrogen (4.70%), and oxygen (10.58%) doping contents. The SCs also exhibit exceptional cyclic stability, maintaining 98.5% of their capacitance after 10,000 charge/discharge cycles. The two-electrode approach provides a super high energy density of 28 Wh kg-1 at a power density of 250 W kg-1 in an alkaline solution, with remarkable cyclability after 10,000 cycles. The study demonstrates the innovative HSC synthesis from BWOSs precursor and cost-effective fabrication of 3D N/O self-doped heteroatom HSC for flexible energy storage.

Bimetal-organic frameworks derived redox-type composite materials for high-performance energy storage.

Electrodes and electroactive materials are crucial components in the development of supercapacitors due to their geometric properties. In this study, bimetal-organic frameworks (Bi-MOFs, ZIF-8@ZIF-67) were utilized as electrode materials for a high-performance hybrid supercapacitor (HSC) by designing a novel synthesis of metallic carbonate hydroxide/oxides. In particular, the Bi-MOFs function as a sacrificial precursor in the synthesis of hollow NiMn(CO3)0.5·0·.11H2O/ZnO@Co3O4 CNCs (NM-CH/ZnO@Co3O4 CNCs) cubic composite materials by a straightforward low-temperature treatment. The NM-CH/ZnO@Co3O4 CNCs exhibited exceptional electrochemical performance with high specific capacity of 196.3 ± 0.08 mAh/g, specific capacitance of 1179 ± 0.10 F g-1 at 0.5 A g-1, and outstanding cycling stability of 98% after 25,000 cycles compared to the other electrode materials. The porous and hollow structure, along with a large surface area, contributed to the enhanced electrochemical properties of the composite material. An HSC was constructed using NM-CH/ZnO@Co3O4 CNCs as the cathode and activated porous carbon (APC) as the anode, resulting in a device with a specific energy of 33 ± 0.12 Wh kg-1 and a power density of 19354 ± 0.07 W kg-1. The use of Bi-MOF electrodes presents new avenues for the development of high-performance energy storage materials, with the potential for industrial energy storage application demonstrated though the successful powering of portable lightbulbs.

Characteristics of hydrogen energy yield in steam gasification of coffee residues.

Coffee residues (CRs) were gasified using a laboratory-scale fluidized bed gasifier with an air/steam mixture as the carrier gas. The gasification was conducted at an equivalence ratio (ER) of 0.3, and different operation temperatures (700, 800, and 900 °C) and steam-to-biomass (S/B) ratios (0, 0.75, and 1.5) were applied. Increasing temperature without steam boosted H2 and CO concentrations in producer gas, raising lower heating value (LHV) and cold gas efficiency (CGE) through endothermic reactions like Boudouard, tar cracking, and water-gas formation. At 900 °C, gas had LHV of 3.76 MJ/Nm3 and CGE of 22.47%. It was elevating temperature from 700 to 900 °C and S/B ratio to 1.5 raised H2 and CO concentrations from 2.04 to 8.60% and from 9.56 to 11.8%, respectively. This also increased LHV from 2.23 to 3.89 MJ/Nm3 and CGE from 11.28 to 25.08%. The steam gasification reaction was found to increase the H2 concentration and was thus considered effective in converting CRs to syngas and increasing energy production. Overall, the study successfully demonstrated the feasibility of steam gasification as a means of converting coffee residues to syngas and increasing energy production. The results also highlighted the importance of operating temperature and S/B ratio in improving the gasification process.

Polylactic acid-based plastic activated NiAl2O4 nanoparticles as highly active positive electrode materials for energy storage supercapacitor.

A simple, low-cost, and environmentally benign process for synthesizing nanostructured NiO/NiAl2O4 on multiple kinds of carbon nanostructures (CNS) is presented. This method develops polylactic acid (PLA) based waste plastic materials for the producing CNS. These composites (NiO@NiAl2O4/CNS) were examined as potential electrodes in supercapacitors (SC) as they exhibit good charge/discharge reversibility and provide adequate specific capacitance values with a maximum being 1984 F/g at 0.5 A g-1. It is noteworthy that the cycling stability of this sample at 10 A g-1 maintained 101.7% of its initial capacity even after 5000 GCD cycles. An asymmetric supercapacitor (ASC) was built and analyzed, with NiO@NiAl2O4/CNS serving as the cathode and activated carbon serving as the anode of the device. The concluded device has an energy density of 58 Wh kg-1 with a power density of 986 W kg-1 and a SCs of 216.5 F/g. The results showed that the materials mentioned are a great option to use as electrode materials in applications involving the storage of energy.

Recovery of aluminum from plastic packages containing aluminum by gasification.

The standing pouch, a packaging material made of multiple layers of plastic and metal, presents a significant challenge for full recycling. Gasification shows promise as a method to recover aluminum from this type of waste and convert it into energy. This study aims to evaluate the efficiency of gasification in treating aluminum-containing plastic packages, and recovering aluminum while identifying the optimal combinations of temperature and equivalence ratio (ER) to achieve the best outcomes. The study achieved a conversion rate of 43.06 wt% to 69.42 wt% of the original waste mass into syngas, with aluminum recovery rates ranging from 35.2 % to 65.3 %. Temperature and ER alterations affected the product distribution, aluminum recovery rate, and aluminum partitioning in the products. The results indicated that the combination of 700 °C, ER = 0.4 would provide the largest amount of syngas about 69.42 %, which is the main product of the gasification process, and therefore, this combination is the most optimal for syngas-yielding purposes. Under the reclaiming aluminum is more prioritized, the combination of 800 °C, ER = 0.6 would be the most optimal condition, the majority of Al in fuel was found in char and fly ash were 67.5 % and 4.81 %, respectively. The study focused on the partitioning of aluminum during the gasification process, which was observed to mainly exist in the form of Al2O3(s), with gaseous species including AlCl3(g), AlH(g), and Al2O(g) due to their medium volatility. As the ER increased, the amount of O2 also increased, leading to more Al2O3(s) formation. In conclusion, this research provides a foundation for further exploration of gasification as a means of energy conversion and metal recovery.

Facile synthesis of polyethyleneimine-modified cellulose nanocrystal/silica hybrid aerogel for CO2 adsorption.

Cellulose nanocrystal (CNC)/silica hybrid aerogel (CSA) was synthesized from CNC and sodium silicate hybridization using the one-step sol-gel method under atmospheric drying. At a weight ratio of CNC to silica of 1:1, the obtained CSA-1 had a highly porous network, a high specific area of 479 m2 g-1, and a CO2 adsorption capacity of 0.25 mmol g-1. Then, polyethyleneimine (PEI) was impregnated on CSA-1 to improve CO2 adsorption performance. The parameters governing CO2 adsorption performance on CSA-PEI, such as temperatures (70-120 °C) and PEI concentrations (40-60 wt%), were investigated systematically. The optimum adsorbent (CSA-PEI50) exhibited an excellent CO2 adsorption capacity of 2.35 mmol g-1 at 70 °C and a PEI concentration of 50 wt%. The adsorption mechanism of CSA-PEI50 was elucidated by analyzing many adsorption kinetic models. The CO2 adsorption behaviors of CSA-PEI at various temperatures and PEI concentrations had the goodness of fit with the Avrami kinetic model, which can correspond to the multiple adsorption mechanism. The Avrami model also showed fractional reaction orders in a range of 0.352-0.613, and the root mean square error is negligible. Moreover, the rate-limiting kinetic analysis showed that film diffusion and intraparticle diffusion resistance controlled the adsorption speed and dominated the subsequent adsorption stages, respectively. The CSA-PEI50 also exhibited excellent stability after ten adsorption-desorption cycles. This study illustrated that CSA-PEI was a potential adsorbent for CO2 capture from flue gas.

Enhancement strategies of poly(ether-block-amide) copolymer membranes for CO2 separation: A review.

Poly(ether-block-amide) (Pebax) membranes have become the preferred CO2 separation membrane because of their excellent CO2 affinity and robust mechanical resistance. Nevertheless, their development must be considered to overcome the typical obstacles in polymeric membranes, including the perm-selectivity trade-off, plasticization, and physical aging. This article discusses the recent enhancement strategies as a guideline for designing and developing Pebax membranes. Five strategies were developed in the past few years to improve Pebax gas transport properties, including crosslinking, mobile carrier attachment, polymer blending, filler incorporation, and the hybrid technique. Among them, filler incorporation and the hybrid technique were most favorable for boosting CO2/N2 and CO2/CH4 separation performance with a trade-off-free profile. On the other hand, modified Pebax membranes must deal with two latent issues, mechanical strength loss, and perm-selectivity off-balance. Therefore, exploring novel materials with unique structures and surface properties will be promising for further research. In addition, seeking eco-friendly additives has become worthwhile for establishing Pebax membrane sustainable development for gas separation.

Yolk-shell silica dioxide spheres @ metal-organic framework immobilized Ni/Mo nanoparticles as an effective catalyst for formic acid dehydrogenation at low temperature.

The novel catalyst with yolk-shell SiO2 NiMo/SiO2 spheres immobilized by zeolitic imidazolate framework (ZIF-67) materials has been successfully prepared. The experimental results indicated that the prepared catalyst exhibits superior performance for hydrogen generation from Formic acid (FA) dehydrogenation without any additives at low temperatures. The catalytic performances of the NixMo1-x/ZIF-67@SiO2 yolk-shell increased with Ni addition ratio increasing. In this research, Ni0.8Mo0.2/ZIF-67@SiO2 yolk-shell could provide the highest catalytic conversion efficiency. This is due to the uniform dispersion of fine metal nanoparticles (NPs) and synergistic effect between the NiMo NPs and ZIF-67@SiO2 supporter. The turn over frequency (TOF) value was approximately 13,183 h-1 at 25 °C through complete FA conversion. H2 selectivity was also approximately 100% with obvious CO-free hydrogen production at 25 °C. Meanwhile, the prepared NiMo/ZIF-67@SiO2 yolk-shell catalyst also shows superior catalytic stability with corresponding 99% activity after 10 cycles. In summary, the catalyst preparation and hydrogen generated from FA dehydrogenation obtained from this research could provide the important information for application in catalyst innovation and waste FA recycling and recovery in the future.

Eco-friendly rice husk pre-treatment for preparing biogenic silica: Gluconic acid and citric acid comparative study.

Carboxylic acid leaching has been established eco-friendly pre-treatment method for producing biogenic silica (BSi) from rice husk. The most urgent issue is for carboxylic acid to promote new readily biodegradable acids and enhance carboxylic acid sustainability in BSi preparation. This research investigates gluconic acid (GA) applicability for biogenic silica preparation from rice husk compared with citric acid (CA). The results demonstrated that GA was preferable to CA on BSi recovery with 89.91% efficiency. Although GA leaching promoted slightly higher silica loss, the primary metal alkali impurities, such as K2O, Na2O, and Al2O3, were effectively removed at 92-93%, 89-93%, 95-97%, respectively. The combination effect of silica loss and high removal impurities resulted in lower rice husk thermal decomposition activation energy. The characteristics of BSi prepared by GA leaching were comparable with CA leaching, mainly mesoporous with 114.06 m2/g of specific surface area and 0.23 cm3/g of the pore volume. In addition, GA leaching was environmentally better than CA leaching, indicated by minor contribution to all environmental impact indices. The findings suggested that GA could be a potential replacement for prevalent carboxylic acids in BSi preparation.

The migration, transformation and control of trace metals during the gasification of rice straw.

This research investigates the trace metals speciation, partitioning and removal in rice straw gasification equipped with an integrated hot gas cleaning (HGC) system. The experiments were conducted by fluidized bed gasifier and controlled at 800 °C with equivalence ratio (ER) varied between 0.2 and 0.4. The experimental results indicated that the concerned trace metals Zn, Cr, Cd, and Pb partitioning in the gas phase were increased significantly with an increase in ER. This is because the exothermic reaction could enhance the trace metals reacted with chlorine and/or sulfur as well as correspondingly formed highly volatile metals compounds. However, other tested metals Cu, Na, K, Ca, Mg partitioning was obviously decreased in the gas phase with ER increasing. These tested metals tend to form oxides speciation leading the variation in their partitioning characteristics. The XRD identification and thermodynamic equilibrium simulation results were also confirmed the tested metals speciation and partitioning characteristics. The dominant gaseous species produced from rice straw gasification, such as KCl(g), NaCl(g), KO(g), K2O(g), ZnCl2(g), CrO2Cl2(g), CuCl2(g), PbCl2(g), PbO(g), and Cd(g), were predicted by thermodynamic equilibrium model. The tested metals removal by adsorbents of hot gas cleaning system was found to be adsorbed in decreasing order as: K > Cr > Ca > Pb > Mg > Cd > Na > Zn > Cu. Activated carbon was used in hot gas cleaning system and showed a good performance for adsorbing tested metals, especially for Pb, Cd, Cr, Ca, K, and Mg. In summary, HGC system is proposed as an effective way for improving the syngas quality and reducing trace contaminants emission in rice straw gasification.

Recycled gypsum board acted as a mineral swelling agent for improving thermal conductivity characteristics in manufacturing of green lightweight building brick.

Lightweight building bricks manufactured from non-hazardous residues incorporating mineral foaming agents have been successfully developed over past two decades. Very little information is available on recycling and reutilization of construction and demolition waste used as the pore foaming agent in manufacturing lightweight brick. In this research, the mineral swelling agent was gypsum board recycled from construction and demolition waste. The mineral swelling agent effect on the characteristics of green lightweight building materials sintered from drinking water purification (DWP) sludge was investigated. Green lightweight building materials were contained up to 50% (wt%) mineral swelling agent and fired at a temperature ranged between 950 °C and 1050 °C. The experimental results indicated that lightweight building materials have successfully sintered between 1000 °C and 1020 °C and added up to 40% (wt%) recycled gypsum board. The sintered building materials have the characteristics of relatively high compressive strength, low bulk density, and thermal conductivity that were in compliance with relevant Taiwan criteria for application in lightweight building materials. To further consider the eco-friendly and environmental safety of lightweight building materials, the recycled gypsum board can act as a good mineral swelling agent, but can also enhance the chemical stabilization and reduce the metals leachability of lightweight materials based on acidic neutralization capacity (ANC) analysis results. To estimate the carbon dioxide emission in manufacturing and transportation of lightweight materials that sintered this experimental conditions, the estimated carbon dioxide reduction rates were approximately 28.6% and 16.7%, respectively, as a result of the energy saving. Experimental results have confirmed that the feasibility of recycled gypsum board used as a swelling agent and good potential for construction works in green lightweight building materials.

Effects of Al-coagulant sludge characteristics on the efficiency of coagulants recovery by acidification.

This study evaluated the effects of Al-coagulant sludge characteristics on the efficiency ofcoagulant recovery by acidification with H2SO4. Two sludge characteristics were studied: types of coagulant and textures of the suspended solid in raw water. The coagulant types are aluminium sulphate and polyaluminium chloride (PACl); the textures of the suspended solid are sand-based and clay-based. Efficiency of aluminium recovery at a pH of 2 was compared for different sludges obtained from water treatment plants in Taiwan. The results showed that efficiency of aluminium recovery from sludge containing clayey particles was higher than that from sludge containing sandy particles. As for the effect of coagulant types, the aluminium recovery efficiency for sludge using PACl ranged between 77% and 100%, whereas it ranged between 65% and 72% for sludge using aluminium sulphate as the coagulant. This means using PACl as the coagulant could result in higher recovery efficiency of coagulant and be beneficial for water treatment plants where renewable materials and waste reduction as the factors for making decisions regarding plant operations. However, other metals, such as manganese, could be released with aluminium during the acidification process and limit the use of the recovered coagulants. It is suggested that the recovered coagulants be used in wastewater treatment processes.

Water washing effects on metals emission reduction during municipal solid waste incinerator (MSWI) fly ash melting process.

This study investigated that water washing effects on the metals emission reduction in melting of municipal solid waste incinerator (MSWI) fly ash. Experimental conditions were conducted at liquid-to-solid (L/S) ratio 10, 20, and 100 for water-washing process and its subsequent melting treatment at 1450 degrees C for 2h. The simple water-washing process as a pre-treatment for MSWI fly ash can remove most of the chlorides, leachable salts, and amphoteric heavy metals from the MSWI fly ash, resulting in the washed ash having lowered chlorine content. MSWI fly ashes washed by L/S ratio 10 and above that were melted at 1450 degrees C produced slag containing relatively high vitrificaton ratio of Cu and Pb. Besides, the vitrification ratios of Na, K, Ca, and Mg in washed MSWI fly ash were also higher than that of MSWI fly ash. The results indicated that washed MSWI fly ash can reduce the emission of metallic chlorides during its subsequent melting treatment.

Lightweight bricks manufactured from water treatment sludge and rice husks.

Novel lightweight bricks have been produced by sintering mixes of dried water treatment sludge and rice husk. Samples containing up to 20 wt.% rice husk have been fired using a heating schedule that allowed effective organic burn-out. Rice husk addition increased the porosity of sintered samples and higher sintering temperatures increased compressive strengths. Materials containing 15 wt.% rice husk that were sintered at 1100 degrees C produced low bulk density and relatively high strength materials that were compliant with relevant Taiwan standards for use as lightweight bricks.

Comparison of leaching characteristics of heavy metals in APC residue from an MSW incinerator using various extraction methods.

This study investigates four extraction methods (water extraction, toxicity characteristics leaching procedure (TCLP), modified TCLP with pH control, and sequential chemical extraction (SCE)), each representing different liquid-to-solid (L/S) ratios, pH controls, and types of leachant, and their effects on the leaching concentration of heavy metals in municipal solid waste (MSW) incinerator air pollution control (APC) residue. The results indicated that for extraction with distilled water, the heavy metal leaching concentration (mg/l) decreased with L/S ratio, but the amount of heavy metal released (AHMR), defined as the leached amount of heavy metals to the weight of the tested sample (mg/kg), increased with an increase in L/S ratio, in the range of 2-100. The results also showed that both the leaching concentration and the amount of released metals were strongly pH-dependent in the TCLP and modified TCLP tests. In the case of pHs lower than 6.5, the leaching concentrations of Cd, Pb, Cu, Zn, and Cr decreased with an increase in pH. As pH increased higher than 6.5, Cr and Zn were almost insoluble. Meanwhile, Cd and Cu also showed a similar trend but at pHs of 8.5 and 7.5, respectively. Due to the nature of amphoteric elements, in the case of pHs higher than 7, the Pb leaching concentration increased with increasing pH. In modified TCLP tests with the pH value controlled at the same level as in the SCE test, the heavy metal speciation approached the extractable carbonate bound fraction by the SCE. Both amounts of targeted metals leached from the SCE and modified TCLP tests were much higher than those for the regular TCLP and water extraction tests.

Study on the characteristics of building bricks produced from reservoir sediment.

This research investigates the feasibility of building bricks produced from reservoir sediment sintering using various sintering temperatures and clay additions. The experimental results indicate that sintered specimen densification occurred at sintering temperatures of 1050-1100 degrees C. Increasing the sintering temperature decreases the water absorption and increases the shrinkage, density and compressive strength of sintered specimens. The experiments were conducted at a temperature ranged from 1050 to 1150 degrees C with clay addition contents varying from 0% to 20%. All sintered specimens made from reservoir sediment were in compliance with Taiwan building bricks criteria. This means that raw materials for producing building bricks can be replaced with reservoir sediment. The metals concentrations of the leachate from the toxicity characteristics leaching procedure (TCLP) test are all complying with the current regulatory limits. These results confirm the feasibility of using reservoir sediment to produce sintered construction brick.

The effects of calcium hydroxide on hydrogen chloride emission characteristics during a simulated densified refuse-derived fuel combustion process.

This study investigated the effects of different calcium hydroxide (Ca(OH)(2)) addition methods on the potential for hydrogen chloride (HCl) formation in a simulated densified refuse-derived fuel (RDF-5) with single metal combustion system. These experiments were conducted at 850 degrees C with the Ca(OH)(2) spiked in the RDF-5 production or injection in the flue gas treatment system. The results indicated that the potential for HCl formation was decreased significantly by Ca(OH)(2) spiked in the RDF-5 production or injection in the flue gas treatment system. However, the Ca(OH)(2) injection method in the flue gas for HCl emission reduction was better than other method. According to the relationship between the HCl emission and amount of Ca(OH)(2) injected or spiked, it is interesting to find that when the Ca(OH)(2) injected or spiked ranged from 0% to 5%, the potential for HCl formation in the single metal combustion system decreases significantly with increasing Ca(OH)(2) injected or spiked ratio. A corresponding increase in the amount of CaCl(2) partitioned to the fly ash was observed. However, with the ratio of Ca(OH)(2) higher than 5%, the amount of HCl formation showed that no further significant variation occurred with increasing Ca(OH)(2) spiked ratio.

Effect of heating temperature on the sintering characteristics of sewage sludge ash.

This study investigated and analyzed the effects of the heating temperature on the properties of the sintered sewage sludge ash. The results indicated that the water absorption rate of the sintered sewage sludge ash samples decreased when the firing temperature was increased from 800 to 900 degrees C. When the heating temperature reached 1000 degrees C, the absorption rate decreased significantly. The bulk density of the sewage sludge ash samples increased by 2.3g/cm3 when the heating temperature was increased from 900 to 1000 degrees C, indicating that the densification was affected by heating. The porosity of the sintered sewage sludge ash samples ranged from 36% to 39% when the heating temperature ranged from 600 to 900 degrees C. The least porosity occurred at 1000 degrees C; the sintered samples were well densified. When the temperature was between 900 and 1000 degrees C, the strength appeared to increase significantly, reaching 2040 kgf/cm2, implying an advance in densification due to sintering. The SEM observations were in general agreement with the trends shown by the density data.

The recycling of MSW incinerator bottom ash by sintering.

In recognition of the trend toward an increased use of bottom ash as construction material, the authors have investigated the feasibility of recovering bottom ash for use as aggregates, by sintering size-fractioned MSW incinerator bottom ash (particle size less than 1.41 mm and between 4.76-1.41 mm) at 400-1,000 degrees C for 60-240 min, and then determining the sintered material characteristics, such as the compressive strength, heavy metal leachability and principal material properties. The results indicate that the pH of the Toxicity Characteristic Leaching Procedure (TCLP) leachate produced from both fine and the coarse ash, ranged from 10.0-11.5, and from 7.5-11.3 respectively, and showed a tendency to decrease with an increasing sintering temperature. In addition, for both types of ash the compressive strength of the sintered monoliths, ranging from 50-55 MPa, decreased slightly when the sintering temperature was increased from 400 to 600 degrees C. Deformation problems may arise from the melting of glassy substances in the ash when bottom ash is sintered at temperatures higher than 700 degrees C. Thus, when sintered between 800 to 1,000 degrees C, the sintered bottom ash pellets might disintegrate due to the formation of aluminium and/or calcium salts. The decomposition of calcium carbonate at 650 degrees C which releases significant amounts of carbon dioxide, may also cause the destruction of a monolith. Based on considerations of loss on ignition, volume changes, water adsorption, soundness, bulk density and the compressive strength of the sintered ash, developed by the sintering of bottom ash between 400 to 600 degrees C after removing its coarse impurities, the general results from the experiments suggest that the aggregates do meet the Chinese National Standards (CNS) for permeable blocks.