•Machine learning techniques predict compressive strength of concrete made with RAC.•GB_PSO is the best Machine Learning model for prediction of compressive strength.•Mix design of concrete made with ...RAC can be estimated with aided of PDP 1D.
To reduce the environmental impact of construction and demolition waste of concrete, recycled concrete aggregate (RCA) has been widely utilized in concrete. The compressive strength of recycled concrete is one of the most important parameters governing the quality of concrete. The compressive strength is determined from the compression test, which requires a huge amount of materials as well as consumes cost and time. Thus, to solve those limitations, this study focused on evaluating the compressive strength of concrete made from RCA using different single and hybrid models of machine learning. Six machine learning models including Gradient Boosting (GB), Extreme Gradient Boosting (XGB), Support Vector Regression (SVR), and three hybrid models of those single models with Particle Swarm Optimization (PSO) namely GB_PSO, XGB_PSO, and SVR_PSO were used to estimate the compressive strength of recycled concrete. The input variables for modeling consisted of cement content, water content, aggregate content, natural aggregate content, recycle concrete aggregate content, sand content, water absorption rates of natural aggregate and RCA. The results of this study show that hybrid models performed better than single models in terms of prediction accuracy. The results indicated that the GB_PSO has the highest prediction accuracy with R = 0.9356, RMSE = 5.5604 MPa, and MAE = 4.2882 MPa. The results of feature importance analysis and partial dependence plots (PDP) analysis revealed that the most important variable effect on compressive strength of concrete made with RAC is cement content, whatever performance strategies of concrete made with RAC. From the results of PDP, the quantity of each material can be computed easily for the designed compressive strength. In the end, this study provides a systematic evaluation of the compressive strength prediction of recycled concrete and has a significant contribution to literature and practice.
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•The CoFe2O4-CeO2 composites were successful synthesized and characterized.•The concentration of primary radical including SO4− and HO was calculated.•The catalytic mechanism in ...15%CoFe2O4-CeO2/PMS system was proposed.•H2PO4− accelerated the atrazine degradation in 15%CoFe2O4-CeO2/PMS system.
CoFe2O4-CeO2 composites with different CoFe2O4 content were synthesized and used as catalysts for peroxymonosulfate (PMS) activation in water purification. Under the conditions of 200 mg/L 15%CoFe2O4-CeO2 and 0.15 mM PMS, complete atrazine degradation was achieved in the 15%CoFe2O4-CeO2/PMS system. The pseudo-first-order rate constant (kobs) in 15%CoFe2O4-CeO2/PMS system (0.224 min−1) was 2.4 and 4.8 times of that in CoFe2O4/PMS system (0.092 min−1) and (CoFe2O4 + CeO2)/PMS system (0.047 min−1). The main reactive species were verified through various quenching experiments and electron paramagnetic resonance tests, and the concentration of two main radicals was calculated. In addition, the interaction between CoFe2O4 and CeO2 involving Co(III)/Co(II), Fe(III)/Fe(II), and Ce(IV)/Ce(III) redox recycle for accelerating the degradation of organic compounds was explored. In addition, different from Cl−, HCO3− and NO3−, H2PO4− could promote atrazine degradation in 15%CoFe2O4-CeO2/PMS system by improving sulfate radical concentration in the reaction system. The main degradation intermediates of atrazine in the 15%CoFe2O4-CeO2/PMS and CoFe2O4/PMS systems were compared, as well as the degradation pathways. The toxicity analysis based on luminescent bacteria Vibrio fischeri indicated the superiority of 15%CoFe2O4-CeO2/PMS than CoFe2O4/PMS systems for ATZ degradation.
Plastic waste upcycling toward a circular economy Zhao, Xianhui; Korey, Matthew; Li, Kai ...
Chemical engineering journal (Lausanne, Switzerland : 1996),
01/2022, Letnik:
428, Številka:
C
Journal Article
Recenzirano
Odprti dostop
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•Plastic waste upcycling to high-value product: liquid fuel, H2, nanomaterial, monomer.•Plastic composition, conversion efficiency, reaction mechanism, catalyst selection.•Compare ...conversion strategies: pyrolysis, gasification, reprocessing, photoreforming.•Polymer design and modification: recyclable polymer, depolymerization, compatibilizer.
Large amounts of plastics are discarded worldwide each year, leading to a significant mass of waste in landfills and pollution to soil, air, and waterways. Upcycling is an efficient way to transform plastic waste into high-value products and can significantly lessen the environmental impact of plastic production/consumption. In this article, current advances and future directions in plastic waste upcycling technologies are discussed. In particular, this review focuses on the production of high-value materials from plastic waste conversion methods, including pyrolysis, gasification, photoreforming, and mechanical reprocessing. Plastic waste compositions, conversion products, reaction mechanisms, catalyst selection, conversion efficiencies, polymer design, and polymer modification are also explored. The main challenges facing the adoption and scale-up of these technologies are highlighted. Suggestions are given for focusing future research and development to increase the efficiency of upcycling practices.
Surface of plants holds huge research potentials: Lotus leaf holds antifouling ability resulted from its surface wax structure and skin of fruits like tomato possesses the outer cuticle providing the ...fruit with protection against rotting. By combining the merits of these two plants: applying main component of cuticle – cutin with membrane forming agent pectin and introducing superhydrophobic beeswax particles modification, the edible artificial lotus leaf (AL) can be fabricated. Moreover, additional heating was introduced for surface stability enhancement. The edible AL could possess application potentials in fields of plant waste recycle, functional packaging, plastic replacement and food application with the additional merits that lotus leaf and tomato skin lacks: assemble and recycle ability.
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•An edible superhydrophobic AL achieved the wettability of lotus surface.•Experiment results indicated the ALs possessed repellence for various food liquids.•The 60 s heated AL hold better stability against water impact.•The 60 s heated AL can serve as edible seal for freshly cut apple.
Edible superhydrophobic surface for food related application has been fulfilled on various substrates; however, the independent edible superhydrophobic material has yet to be realized. Here we report the edible artificial lotus leaf (AL) fabricated through combination of superhydrophobic beeswax coating and tomato waste recycled cutin-pectin membrane, mimicking the antifouling ability of lotus and oxygen barrier ability of tomato. Moreover, additional heating was introduced for stability enhancement, increasing adhesion and water vapour blocking ability. Through the combination of Merits of both lotus leaf and tomato skin, results indicated that AL could be presented as an independent food packaging and form straw, cup and dissolvable bag as plastic replacement material. Furthermore, AL could serve as recyclable functional packaging for underwater storage, oxidation blocking, selective release bags. Additionally, AL holds similar mechanical strength to tomato peel. Therefore, edible AL can provide new insights for future edible superhydrophobic material and food packaging designs.
Solar-assisted distillation is considered promising to solve the freshwater supply for off-grid communities. In this work, a passive and flexible multistage membrane distillation (F-MSMD) device is ...devised to produce freshwater via solar distillation with the latent heat of vapor condensation being recycled to enhance its energy efficiency. By designing a siphon effect, source water is continuously wicked into the evaporation layer and the concentrated brine flows out of the device before reaching saturation, which successfully solves the otherwise challenge of salt accumulation inside the device. To achieve such siphon flow, the recycled paper is prepared from spent copy paper and used as the evaporation layer for efficient water delivery owing to its large pore size and high hydrophilicity. An eight-stage F-MSMD device exhibits a stable clean water production rate at 3.61 kg m–2 h–1 in the newly designed siphon-flow mode. This work provides a green route for designing a solar-assisted distillation device.
In recent years, with the continuous development of industry and agriculture, the content of organic pollutants in the environment has been increasing, which has caused serious pollution to the ...environment. Adsorption has proven to be an effective and economically viable method of removing organic contaminants. Since biochar has many advantages such as various types of raw materials, low cost, and recyclability, it can achieve the effect of turning waste into treasure when used for environmental treatment. This paper summarizes the source and production of biochar, points out its research status in the removal of organic pollutants, expounds its adsorption mechanism on organic pollutants, introduces the relevant adsorption parameters, summarizes its regeneration methods, studies its application of engineering, and finally analyses of benefits and describes the development prospects.
•Recent research on adsorbing organic contaminants by biochar were summarized.•Mechanism of organic contaminants adsorption using biochar.•The application of biochar as adsorbents in engineering was introduced.•Biochar as an adsorbent needs to continue to explore in the future was proposed.
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•Co3O4-BiVO4/g-C3N4 composites was synthesized via a green and effective method.•The composites displayed excellent photocatalytic activities and stability.•ESR and trapping tests ...indicated h+ and O2− were the main active species.•The possible photocatalytic mechanism was also proposed.
In this study, a novel coral-like Co3O4-BiVO4/g-C3N4 ternary composite catalyst was successfully synthesized via high temperature polymerization and controlled hydrothermal reaction. In the Co3O4-BiVO4/g-C3N4 ternary hybrid system, the bulk Co3O4 particles were uniformly dispersed on the coral-like BiVO4 nanosheet, which not only enhanced to increase the response range and absorption to visible light, also contributed to suppress the recombination of photogenerated electron holes. The introduction of flocculent g-C3N4 increased the specific surface area of the catalytic system while accelerating the transmission efficiency of photogenerated carriers. After being illuminated for 90 min under the visible light, the degradation efficiency of pure BiVO4 and g-C3N4 catalysts were 81% and 80.2%, respectively. And the two binary catalysts, Co3O4-BiVO4 and BiVO4/g-C3N4 composite catalyst, performed the higher photocatalytic activity, which reached 94.8% and 96.8%, while ternary catalyst Co3O4-BiVO4/g-C3N4 composite catalyst showed the highest photocatalytic activity, the removal rate of KN-R was up to 99.6% after being irradiated for only 30 min with visible-light. Even more, its optical and electrochemical properties were greatly improved, making it as a forceful candidate for practical photocatalysts under visible light. In summary, this work not only provided a highly efficient heterojunction-structured visible-light photocatalyst, but also supplied a novel method to diminish the photo-carriers recombination.
Metal–CO2 batteries show great promise in meeting the growing energy, chemical, and environmental demands of daily life and industry, because of their advantages of high flexibility and efficiency in ...both energy storage and CO2 recycle applications. It has been a trend that Li/Na‐CO2 and Zn/Al‐CO2 systems show different developments to achieve practical energy storage (e.g., high electricity supply) and CO2 recycling (e.g., flexible chemical production), respectively, which is often neglected. This inhibits the application of metal–CO2 batteries in maximizing energy supply and value‐added CO2 conversion. This progress report presents a critically selected overview of the individual developments of metal–CO2 batteries with emphasis on diverse fundamental origins, performance advantages, and the future of these two systems. Furthermore, the reaction pathways, particularly for catalytic materials, for the Li/Na‐CO2 and Zn/Al‐CO2 systems are discussed. Finally, the challenges of these two systems along with a hybrid Li/Na‐CO2 battery design that may simultaneously provide high operating voltages and flexible chemicals are outlined.
Individual development of metal–CO2 batteries mainly due to different CO2 reaction mechanisms and anodes with different activities presents the Li/Na‐CO2 system for high‐efficiency energy storage and Zn/Al‐CO2 system for flexible chemical production. By specifically designing catalytic materials for two systems, metal–CO2 batteries will better meet the growing and ever‐changing energy, chemical, and environmental demands for sustainable daily life and industry.
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•Pd NPs supported ordered mesoporous were synthesized.•Pd NPs were characterized by XPS, XRD, TEM, SEM, FT-IR and NMR spectroscopy.•Catalyst loading, temperature, NaOH and NaBH4 ...concentration effects were examined.•Pd NPs catalyze the hydrolytic production of H2 from NaBH4 with TOF of 176 moleH2.molcat−1.min−1.•Pd NPs catalyst retains 71.6% of its initial catalytic activity after five cycles.
The ordered mesoporous silica supported Pd NPs, denoted as Pd NPs@KIT-6 2 and Pd NPs@KIT-6-PEG-imid 6, were synthesized by a deposition precipitation method using the KIT-6 1 or KIT-6-PEG-imid 5, respectively, and Na2PdCl4 followed by in situ reduction by NaBH4. The obtained supported Pd NPs 2 and 6 were fully characterized by XPS, XRD, TEM, SEM, FT-IR and solid-state 29Si and 13C NMR spectroscopy. The effect of several parameters such as catalyst loading, temperature, NaOH and NaBH4 concentration were examined to obtain the optimum reaction conditions. The supported Pd NPs 2 and 6 catalyze the hydrolytic production of H2 from NaBH4 with notable efficiencies and the catalyst stabilized by PEG and imidazolium ionic liquid based-KIT-6 6 is more active than its KIT-6 counterpart 2. A TOF of 176 moleH2.molcat−1.min−1 for 6 was achieved when the reaction was performed with a low catalyst loading of 0.1 mol%. Reaction kinetics studies showed that the hydrolysis is first order in catalyst and NaBH4 with apparent Ea of 35.0 and 35.7 kJ mol−1 for 2 and 6, respectively. The efficiency of catalyst 6 for the hydrolysis of NaBH4 was investigated in H2O and D2O and indicated that the reaction is considerably faster in H2O than in D2O with primary KIE kH/kD = 2.36. In addition, the PdNPs based KIT-6 mesoporous silica 6 retains 71.6% of its initial efficiency after five cycles.
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