Microwave-assisted and conventional hydrothermal carbonization of lignocellulosic waste material: comparison of the chemical and structural properties of the hydrochars

This study compares the chemical and structural properties of the hydrochars prepared from microwave-assisted and conventional hydrothermal carbonizations of Prosopis africana shell, a waste plant material. The preparation involved heating the raw material in de-ionized water at 200 °C for 5-20 min, and 120-240 min in the microwave and conventional oven respectively. The prepared hydrochars were characterized using the scanning electron microscope, nitrogen sorption measurement, Fourier transform infrared spectroscopy, CHN analyzer, thermogravimetric analysis, and nuclear magnetic resonance. The results showed that the microwave-assisted hydrothermal carbonization process is fast in the carbonization of the Prosopis africana shell as shown by the level of conversion attained within the short time. This study presents new data on the comparison of the hydrochars from microwave-assisted and conventional hydrothermal carbonization processes of the same lignocellulosic material in terms of their properties

Biomass derived mesoporous carbon monoliths via an evaporation-induced self-assembly

Evaporation-induced self-assembly has been applied in the synthesis of crack-free mesoporous carbon monolith with good mechanical stability using a waste plant material as carbon precursor and triblock copolymer F127 as template. The carbon monolith was characterized using transmission electron microscopy, scanning electron microscopy, nitrogen adsorption–desorption measurement, X-ray diffraction and Fourier transform infrared spectroscopy. The results showed that the carbon monolith is mesoporous, has a surface area of 219 m²/g, and a narrow pore size distribution of 6.5 nm

Microwave-assisted hydrothermal carbonization of rapeseed husk: A strategy for improving its solid fuel properties

Hydrothermal carbonization of a waste biomass material is a green and promising technique for improving its solid fuel properties, which does not require pretreatment procedure such as drying of the biomass. In this study, hydrothermal carbonization of rapeseed husk, a waste plant material was carried out under microwave heating and the effect of process parameters, such as reaction temperature and residence time on the mass yields and energy properties of the hydrochars was studied. The procedure involved the heating of the feedstock in deionized water in a microwave oven at temperatures of 150 to 200 °C for a specified period of time. The results indicated that the mass yields decreased, as the reaction temperature and residence time were increased, which led to improvement in the energy properties of the prepared hydrochars. The reaction was rapid within the first 20 min, and stabilized afterwards. The energy properties of the prepared hydrochars are consistent with previous studies, showing that the hydrochars have the potential of being used as solid fuel. The structural and morphological analysis carried out revealed that the feedstock was transformed during the process

Characterization of energy-rich hydrochars from microwave-assisted hydrothermal carbonization of coconut shell

In this study, microwave-assisted hydrothermal carbonization of waste coconut shell (feedstock) is reported. It is a thermo-conversion technique in which the feedstock was transformed into energy-rich carbonaceous material under mild conditions. The process was conducted in a microwave oven by heating the waste coconut shell in deionized water inside a pressurized vessel. The effects of different process conditions on the product yields, and the energy properties of the hydrochars were studied by varying the reaction temperature from 150 to 200 °C and residence time from 5 to 30 min. The results showed that there was transformation of the feedstock in the process due to the decarboxylation, dehydration, and demethanation reactions. This led to changes in the chemical and structural compositions, as well as increase in the energy properties of the prepared hydrochars. The higher heating value increased from 15.06 MJ/kg in the feedstock to 19.76 MJ/kg in the hydrochar. The energy properties of the hydrochars prepared in this study showed that microwave-assisted hydrothermal carbonization process could be a technique for converting waste coconut shell into high value-added product

Microwave-assisted hydrothermal synthesis of carbon monolith via a soft-template method using resorcinol and formaldehyde as carbon precursor and pluronic F127 as template

A new microwave-assisted hydrothermal synthesis of carbon monolith is reported in this work. The process uses microwave heating at 100 °C under acidic condition by employing a triblock copolymer F127 as the template, and resorcinol–formaldehyde as the carbon precursor. Scanning electron microscopy, Fourier transform infrared spectroscopy, nitrogen sorption measurements, transmission electron microscopy, X-ray studies and thermogravimetic analysis were used to characterize the synthesized material. The carbon monolith is crack-free, mesoporous and has a high surface area of 697 m²/g. The results demonstrate that the microwave-assisted hydrothermal synthesis is a fast and simple approach to obtain carbon monoliths, as it reduces effectively the synthesis time from hours to a few minutes which could be an advantage in the large scale production of the material

Synthesis, characterization and antimicrobial activity of mixed transition metal complexes of salicylic acid with 1, 10-phenanthroline

A new series of Mn(II), Fe(II), Co(II), Cu(II) and Zn(II) mixed ligands-metal complexes derived from salicylic acid (SA) and 1,10-phenanthroline (PHEN) have been synthesized and characterized by spectroscopic studies. The coordination of the two ligands towards central metal ions has been proposed in the light of elemental analysis, IR, UV–vis spectroscopic studies. The results of the physical and spectroscopic data confirmed that the ligands are chelating agents. In 1, 10-phenanthroline, coordination occurred through the two pyridinic nitrogen groups, while in the salicylic acid coordination occurred through the oxygen of the hydroxyl and the carboxylic groups. All the complexes synthesized were of octahedral geometry. Antimicrobial activity of the mixed ligands metal complexes and the free ligands were carried out against the bacterial Escherichia coli, staphylococcus aureus, klebsiella pneumonia, pseudomonas aeruginosa and the fungi candida spp. The mixed ligands metal complexes showed higher activities when compared to the free ligands of salicylic acid but were less active than the free 1,10-phenanthroline ligand. The complexes of Cu (II) showed the highest antimicrobial activity while the Fe(II ) complex showed the least activity against the bacterial and fungi organisms.Keywords: 1,10-phenanthroline, Salicylic acid, Mixed ligands-metal complexes, Transition metal, Spectroscopy, Antimicrobia

The effect of anthracene on total dry matter and extracellular enzyme analysis of a starch-amended composting process

<p>Composting technology has been widely used as a cost-effective, eco-friendly, and efficient solid waste management option for the bioremediation of organic pollutants. Most studies have focused on the use of compost in the bioremediation of organic pollutants, without any attention being paid to the effect of the organic pollutants on the composting process. Therefore, in this study, the effect of an organic pollutant (anthracene) on a starch-amended composting process is reported. In order to determine the effect, the total dry matter and the extracellular enzyme analysis (EEA) of starch-specific (α-glucosidase) and -nonspecific (β-glucosidase) substrates were monitored. Over the course of the experiments, there appeared to be some form of anthracene effect on the progression in the total dry matter and the extracellular enzyme analysis (EEA) of the α-glucosidase, particularly in the starch and anthracene–amended composts. The interactions between the starch and the anthracene consistently increased the total dry matter and the α-glucosidase activity of the starch and anthracene–amended composts. This observation is novel, and the kind of interaction is yet unknown. Therefore, detailed investigation to understand the magnitude of such interaction is necessary to potentially resolve these issues.</p