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Microwave assisted synthesis of 5-hydroxymethylfurfural (HMF) using hydrolysate produced from dilute acid hydrolysis of bamboo with low transition temperature mixture (LTTM) as a green solvent was performed. Bamboo was a fast-growing plant with high cellulose content in the biomass, which made it suitable as the raw material for HMF production. LTTM was produced from hydrogen bond acceptor and donor, which in this study were choline chloride and malic acid, respectively. Microwave irradiation was used as it is faster and energy saving than conventional heating methods. A two-factors three-levels full factorial design with temperature and reaction time as the manipulating variables was employed and a linear model was constructed with R2 of 0.9640 and p-value of 0.0115, indicating good reliability and significant. ANOVA analysis informed that only the temperature was significant, where the optimum point was 120 °C and 10 min with HMF yield of 10.7951 %. A follow up study was conducted at 140 °C and 5 min and had found that the system established an equilibrium of temperature at 120 °C between the heat loss by evaporation of water and heat gained by microwave irradiation. The shorter reaction time also resulted in higher HMF yield of 10.9410 %, possibly due to lower degree of unwanted side reaction (i.e., rehydration of HMF into levulinic acid). This study shows that it is possible to directly utilise the hydrolysate of bamboo without further separation of glucose in conversion into HMF, a valuable green and sustainable platform chemical. [ABSTRACT FROM AUTHOR]

Emission of greenhouse gases is currently recognized as one of the most significant problems confronting societies all over the world. Human activities, such as the consumption of fossil fuels for the generation of heat and electricity, as well as other industrial operations and transportation, are the primary sources of greenhouse gas emissions. The implementation of adsorption technology for the capture of carbon are widely used to lower the greenhouse gas emissions mainly carbon dioxide (CO2). However, there are still insufficient research has been done on the performance of Meranti sawdust as a low-cost carbon for CO2 capture, particularly by using a greener activation agent. A mechanochemical activation method using potassium carbonate (K2CO3) is highlighted in this study, where the approach is simpler and more environmentally friendly. By using the Taguchi L9 orthogonal array, several variables (i.e., temperature, impregnation ratio, duration, N2 flow rate) have been investigated to determine the optimal operating conditions to obtain high yield activated carbon. From the findings, it is shown that the optimal conditions for the activated carbon production is at 700 °C, impregnation ratio of 3:1, carbonization time of 60 min, and N2 flow of 900 mL/min, with corresponding activated carbon yield is approximately 41 % and CO2 adsorption capacity of 2.8 mmol/g. The carbon materials are to be evaluated in terms of elemental composition, surface functionalities and morphologies, as well as textural characteristics. Overall, wood waste conversion to activated carbon aligns with SDG 9, SDG 12, as well as SDG 13. [ABSTRACT FROM AUTHOR]

BACKGROUND: Over the years, activated carbon has been widely used for environmental applications, including liquid or gas phase applications. However, there are many hurdles for researchers in the activated carbon field to overcome when it comes to non‐renewable materials, the utilization of individual precursors, and the complex multistep procedures of activated carbon synthesis. Therefore, in this study, the facile mechanochemical potassium carbonate (K2CO3) activation of blended precursors — palm kernel shell and petroleum coke — was investigated in terms of the activated carbon yield and carbon dioxide (CO2) adsorption capacity. RESULTS: The optimum configuration of the activated carbon production was found at temperature of 680°C, holding time of 60 min, and impregnation ratio of 1.75:1. The CO2 adsorption data at 25–120°C was best represented by the Sips model with R2 > 0.9999, where maximum CO2 adsorption capacity (qmax) was within the range of 2.24–4.32 mmol/g. The kinetic analysis was well‐represented by the pseudo‐second order model due to the high R2 and low sum of square of errors (ERRSQ) value. In terms of thermodynamic analysis, it showed that the CO2 adsorption process was physical, exothermic, and spontaneous at lower temperature. CONCLUSION: Overall, the integration of agricultural and industrial waste to value‐added activated carbon was feasible not only in reducing waste disposal problems but also in facilitating CO2 mitigation. © 2022 Society of Chemical Industry (SCI). [ABSTRACT FROM AUTHOR]

Bamboo is the fastest-growing plant and is abundant in Malaysia. It is employed as a starting material for activated carbon production and evaluated for its potential in CO2 capture. A single-stage phosphoric acid (H3PO4) activation is adopted by varying the concentrations of H3PO4 between 50 and 70 wt.% at a constant temperature and holding time of 500°C and 120 min, respectively. The bamboo-based activated carbons are characterized in terms of product yield, surface area, and porosity, as well as surface chemistry properties. Referring to the experimental findings, the prepared activated carbons have BET surface area of >1000 m2 g-1, which implies the effectiveness of the single-stage H3PO4 activation. Furthermore, the prepared activated carbon via 50 wt.% H3PO4 activation shows the highest BET surface area and carbon dioxide (CO2) adsorption capacity of 1.45 mmol g-1 at 25°C/1 bar and 9.0 mmol g-1 at 25°C/30 bar. With respect to both the characterization analysis and CO2 adsorption performance, it is concluded that bamboo waste conversion to activated carbon through H3PO4 activation method is indeed promising. [ABSTRACT FROM AUTHOR]

The volumetric adsorption kinetics of carbon dioxide (CO2) onto the synthesized palm kernel shell activated carbon via single-stage CO2 activation and commercial Norit® activated carbon were carried out at an initial pressure of approximately 1 bar at three different temperatures of 25, 50, and 100 °C. The experimental kinetics data were modelled by using the Lagergren's pseudo-first-order model and pseudo-second-order model. Comparing these two, the non-linear pseudo-second-order kinetics model presented a better fit towards CO2 adsorption for both adsorbents, owing to its closer coefficient of determination (R2) to unity, irrespective of the adsorption temperature. In addition, kinetics analysis showed that the corresponding kinetics coefficient (rate of adsorption) of both activated carbons increased with respect to adsorption temperature, and thereby, it indicated higher mobility of CO2 adsorbates at an elevated temperature. Nevertheless, CO2 adsorption capacity of both activated carbons reduced at elevated temperatures, which signified exothermic and physical adsorption (physisorption) behaviour. Besides, process exothermicity of both carbonaceous adsorbents can be corroborated through activation energy (Ea) value, which was deduced from the Arrhenius plot. Ea values that were in range of 32–38 kJ/mol validated exothermic adsorption at low pressure and temperature range of 25–100 °C. To gain an insight into the CO2 adsorption process, experimental data were fitted to intra-particle diffusion model and Boyd's diffusion model, and findings revealed an involvement of both film diffusion and intra-particle diffusion during CO2 adsorption process onto the synthesized activated carbon and commercial activated carbon. [ABSTRACT FROM AUTHOR]