Synergistic Effects of Catalyst Mixtures on Biomass Catalytic Pyrolysis

Kinetics of In-Situ Catalytic Pyrolysis of Rice Husk Pellets Using a Multi-Component Kinetics Model

Ash-based catalysts, as low-cost materials, are applicable in biomass pyrolysis and play a role in lowering the activation energy. This study enriched the insights of different method of catalyst addition into biomass in the catalytic pyrolysis. The addition of rice husk ash as a catalyst into rice husk pellets allows for better solid-solid contact between the biomass and the catalyst, since the common methods were only solid mixing. This research aimed to investigate the thermal characteristics and kinetics of the biomass components (hemicellulose, cellulose, lignin) in the in-situ catalytic pyrolysis of rice husk pellets with the addition of husk ash. The three-independent parallel reaction kinetics model was used to calculate the kinetics parameters based on thermogravimetric analysis conducted at 303-873 K with various heating rates (5, 10, 20 K/min) and ash addition ratios (10:0, 10:1, 10:2). The thermogram shows that the pyrolysis of rice husk pellets was divided into two stages. Stage 1, ranging from 510-650 K, represented the decomposition of hemicellulose and cellulose, occurring faster with high mass loss, while Stage 2, starting at around 650 K, represented lignin decomposition, occurring more slowly with low mass loss. The catalytic activity of the ash was only apparent at high temperatures, where cellulose and lignin decomposition were more dominant. Activation energy, as a representation of catalytic activity for each component, was not always lower in catalytic pyrolysis. However, the average activation energy decreased with increasing heating rates and ash addition ratios. The addition of the catalyst slowed the decomposition of hemicellulose but accelerated the decomposition of cellulose and lignin. Copyright © 2023 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0). 

Microplastic removal from urban stormwater: Current treatments and research gaps

Stormwater is a major contributor to microplastic (MP) pollution in the aquatic environment. Although MPs are associated with many toxicological effects, their levels in stormwater are not regulated. This review compared the effectiveness of different MP removal technologies from stormwater runoff and examined the performance of typical stormwater treatment systems for MP removal to assess possible MP pollution control via stormwater management. Bioretention and filtration systems performed similarly with 84-96% MP removal efficiencies. Despite the limited number of studies that focused on wetlands and retention ponds, preliminary data suggested potential for MP removal with efficiencies of 28-55% and 85-99%, respectively. Despite the higher efficiency of bioretention and filtration systems, their removal efficiency of fibrous MPs was not optimal. Furthermore, wetlands were less effective in removing MPs than retention ponds, although the limited data might lead to an inaccurate representation of typical performances. Therefore, more research is required to arrive at definitive conclusions and to investigate alternative treatment options, such as ballasted sand flocculation, flotation, and biological degradation, and evaluate the effectiveness of bioretention and filtration for MPs <100 μm.

Adsorption of p-benzoquinone at low concentrations from aqueous media using biosolid-based activated carbon

The toxic oxidation intermediate p-benzoquinone exists in aqueous environments at dilute concentrations above the fish-toxicity limit of 0.045 mg/L, affecting aquatic life. The reduction of this compound to the concentrations required to achieve safe discharge limits is challenging. In this study, the adsorptive removal of p-benzoquinone by a biosolid-based activated carbon (SBAC) was systematically investigated in batch experiments. The adsorption rate was rapid, and the bulk of p-benzoquinone adsorption occurred within 30 min. The maximum adsorption capacity of SBAC was estimated at 19.6 mg/g using the Langmuir isotherm model. Its adsorptivity was independent of temperature from 6 to 40 °C. The presence of 6 g/L of chloride and 500 mg/L of sulphate did not affect the removal of 1 mg/L p-benzoquinone, whereas 15 mg/L of humic acid media slightly decreased the p-benzoquinone removal from 87.0% to 83.2%. Diffusion, hydrophilic, and electrostatic interactions (i.e., dipole-dipole) govern the adsorption of p-benzoquinone and are influenced by the SBAC surface chemistry. Biosolid-based activated carbon can lower the residual p-benzoquinone to below the fish-toxicity limit of 0.045 mg/L within 1 h of sequential adsorption. Thus, biosolid-based activated carbon can effectively remove p-benzoquinone from aqueous environments; this is a waste-to-resource approach that addresses sustainability (waste disposal) and environmental protection (pollutant removal).

A new approach to obtain kinetic parameters of corn cob pyrolysis catalyzed with CaO and CaCO3

A new approach is proposed to obtain the kinetic parameters of biomass pyrolysis mixed with calcium catalyst. This approach involves the optimization of least squares (LS) with the Coats-Redfern integral method to avoid mathematical biases that may appear when applying the linear regression approach. The method was applied to the TGA data of pyrolysis of corn cob and corn cob mixed with 20 or 40 % by weight of CaO or CaCO₃ under N₂ atmosphere at temperatures between 25 and 700 °C. For raw cob, r² reaches 0.997. For corn cob mixed with 20 % by weight of CaO or CaCO₃, r² reached 0.996–0.998, and for 40 % by weight, r² reached 0.836–0.957. Applying this method, the activation energy (EA) value of the raw cob pyrolysis is 58.35 kJ mol⁻¹, while the addition of CaO or CaCO₃ increases the EA to 69.33 and 66.07 kJ mol⁻¹, respectively. The method is simple to use and allows reliable values of kinetic parameters.

•

LS regression is a simple method to obtain kinetic parameters from pyrolysis of corn cob.

•

Calcium compounds mixed with corn cob reduce thermal degradation in pyrolysis.

•

The addition of CaO or CaCO₃ to corn cob pyrolysis showed a second- order reaction.

Effects of the COVID-19 pandemic on the environment, waste management, and energy sectors: a deeper look into the long-term impacts

The COVID-19 pandemic not only has caused a global health crisis but also has significant environmental consequences. Although many studies are confirming the short-term improvements in air quality in several countries across the world, the long-term negative consequences outweigh all the claimed positive impacts. As a result, this review highlights the positive and the long-term negative environmental effects of the COVID-19 pandemic by evaluating the scientific literature. Remarkable reduction in the levels of CO (3 - 65%), NO₂ (17 - 83%), NO_x (24 - 47%), PM_2.5 (22 - 78%), PM₁₀ (23 - 80%), and VOCs (25 - 57%) was observed during the lockdown across the world. However, according to this review, the pandemic put enormous strain on the present waste collection and treatment system, resulting in ineffective waste management practices, damaging the environment. The extensive usage of face masks increased the release of microplastics/nanoplastics (183 to 1247 particles piece^-1) and organic pollutants in land and water bodies. Furthermore, the significant usages of anti-bacterial hand sanitizers, disinfectants, and pharmaceuticals have increased the accumulation of various toxic emerging contaminants (e.g., triclocarban, triclosan, bisphenol-A, hydroxychloroquine) in the treated sludge/biosolids and discharged wastewater effluent, posing great threats to the ecosystems. This review also suggests strategies to create long-term environmental advantages. Thermochemical conversions of solid wastes including medical wastes and for treated wastewater sludge/biosolids offer several advantages through recovering the resources and energy and stabilizing/destructing the toxins/contaminants and microplastics in the precursors.