Search

Interaction between the microwave heating rate and dielectric properties of agricultural wastes is important in identifying suitable microwave operating conditions. This work focuses on the interaction between microwave heating rate (power intensity) and dielectric properties of selected agricultural wastes, namely castor shell, empty fruit bunch and palm kernel shell. Heating rate was recorded every 30 s for 10 min in a 2.45 GHz microwave at power intensities of 100, 300, 450, 600, 700 and 800 W. All materials tested display an increase in heating rate with increasing power intensity. Castor shell and empty fruit bunch at 800 W, and palm kernel shell at 600 W exhibit high heating rates of 0.134, 0.165, 0.247 °C/s, respectively. For dielectric properties, palm kernel shell series shows a high value of loss tangent compared to the other counterparts, indicating its effectiveness to be heated via microwave.

Dye is a major source of water pollution. This mini-review highlights the origin of dye, its removal strategies, and the recent literature of methylene blue and Congo red adsorption by activated carbons. Adsorption is a unique process that relies upon the physicochemical properties of the activated carbon and the inherent characteristics of dye. Also, factors affecting adsorption, such as contact time, temperature, and concentration, were discussed to gain insight into dye removal mechanisms.

Nanofluids contain nanometer-sized particles in suspension to enhance heat transfer by increasing the thermal conductivity. This paper provides an overview of particle size and volume fraction of nanofluids, and their roles in enhancing the heat transfer. Often, the transfer of heat is enhanced by dispersed particles with small diameter and high concentration despite some debate about the governing effects. The design of elliptical cross-section and zigzag tube also sheds insight into augmenting heat transfer for future research directions and applications.

Solid fuel briquette from biomass materials has gained considerable attention as sustainable replacement source of energy. The characteristics of briquette are imperative to ensure its effectiveness as fuel in a long run. This paper is aimed to summarize the key properties of solid briquette made from various natural and waste-based resources, and to highlight the future research directions in the briquette manufacture. The commentary is expected to shed insight towards the greener, cleaner, and efficient briquette materials.

This work was aimed at evaluating the adsorptive characteristics and two-stage adsorber design of banana peel adsorbents for malachite green and methylene blue removal. The adsorbents were characterized for specific surface, functional groups, and morphology. Activated carbon and hydrochar activated carbon exhibit similar textural and surface properties, but different capacities of malachite green and methylene blue. The latter with surface area of 877 m2/g endows a greater malachite green removal at 582 mg/g, while the former with surface area of 897 m2/g displays a higher methylene blue capacity of 503 mg/g. The Langmuir model was employed in a two-stage adsorber design. The second stage of adsorber is necessary to accomplish the adsorption process with high performance and minimum dosage of activated carbon.

This work was aimed at optimizing the adsorbent mass and contact time and evaluating the performance of two-stage batch adsorber of NaOH-activated coconut shell carbon for methylene blue removal. To decrease the dye concentration from 1000 to 89.4 mg/L at any effluent volumes, the two-stage adsorber displays a small mass saving of 0.33% because of the high adsorbent affinity towards methylene blue at 1.80 L/mg. Meanwhile, the contact time can be minimized by 97.6% as opposed to that in one-stage adsorber. The sensitivity analysis of affinity on mass minimization shows a significant saving of 28.5% when the affinity is reduced to 0.01 L/mg. The response surface methodology was used to optimize the two-stage absorber for methylene blue removal, wherein the most significant parameter is the contact time.

The present work was aimed to evaluate the optimum mass of crab shell biochar and adsorption contact time in a two-stage adsorber design for malachite green. The model was developed to predict optimum adsorbent mass and adsorption profiles at specified volumes and concentrations of dye effluent. Results show that the adsorbent mass can only be reduced by 1.91 % because of the adsorbent’s strong affinity towards malachite green. Accordingly, the adsorption contact time to achieve equilibrium has dramatically reduced from 150 min to 31 min. In the performance evaluation, the adsorbent mass in stage-1 is always higher than that in stage-2 to subside the adsorbent load in achieving the target removal at optimum dosage. From the response surface methodology, the most significant parameters in two-stage adsorber design are adsorption time at stage-2 and malachite green concentration. The predicted values of adsorbent mass and time are essential in designing the cost-competitive two-stage adsorption process for industrial wastewater treatment.

The exclusive properties of β-cyclodextrin (β-CD) combined with its harmless characters making it as an interesting and potential carbon adsorbent for water pollutants removal via adsorption. This work was aimed at evaluating the kinetics and isotherm parameters of methylene blue dye adsorption onto β-CD polymers. The carbon polymers were prepared by citric acid cross-linking, followed by post-treatment with sodium p-toluenesulfinate. The adsorbents were characterized using TGA, BET and FTIR. The adsorption of methylene blue was studied at varying concentrations (5–300 mg/L) and contact times (10–2880 min), and the kinetics and isotherm models were employed to describe the adsorption data. The post-treated carbon polymer exhibits a greater specific surface of 16.6 m2/g. The maximum adsorption of methylene blue by cross-linked and post-treated β-CD adsorbents are 263 and 227 mg/g, respectively. The kinetics data fitted well into pseudo-first order model, indicating physical adsorption. The Boyd’s model showed that film diffusion may be the controlling mechanism. The equilibrium data of methylene blue adsorption for the two β-CD polymers obeyed Langmuir model. To conclude, β-CD is a promising adsorbent candidate for the treatment of dye wastewater.

The objective of the present work was to evaluate the performance of two-stage adsorber of activated carbon from oil palm empty fruit bunch for methylene blue removal. The model was developed to predict optimum adsorbent mass and time at a specified volumes and concentrations of dye solution. Results show that the adsorbent mass can be reduced by 6.67%. Operating time taken to attain the equilibrium in a two-stage adsorber has dramatically decreased from 22 h to 0.52 h. In the performance evaluation, the adsorbent mass in stage-1 is higher than in stage-2, which lessen the workload to achieve equilibrium. A two-stage adsorber aids to optimize the mass and contact time for different percentage of dye removal that economically feasible for industrial applications.

One of the goals of Sustainable Development Goals (SDG) is to conserve natural resources, such as water, soil, air, and others. Poorly treated industrial effluents discharged into nearby water streams contribute to water pollution. This problem is notably worse among small- and medium-scale industries, such as the local batik industry, which cannot afford proper and costly wastewater treatment facilities in their premises. Batik entrepreneurs should adopt environmentally friendly methods by using currently available technologies. Therefore, this phenomenological study investigated the environmental awareness of three batik entrepreneurs in Malaysia via interviews. The data was analyzed using thematic analysis. The batik entrepreneurs have adopted different batik making processes but employed almost similar batik waste disposal methods. Despite some level of environmental awareness among the batik entrepreneurs, they still practiced poor environmental batik making and disposal methods due to the lack of affordable technology. The lack of exposure to environmental education, open mindset, the socio-cultural practice of batik making, and production cost influences environmental awareness among batik entrepreneurs. Authorities should advocate green batik making and regulate rules for any malpractice. Future studies should explore the effective technologies used to dispose of batik waste effluents to enable batik entrepreneurs to adopt environmentally friendly batik making and waste disposal methods.