Thermogravimetric and kinetic studies of metal (Ru/Fe) impregnated banana pseudo-stem (Musa acuminate)

The effect of ZnSO4 and Fe2(SO4)3 on the pyrolysis of cocoa shells: A tg-FTIR study

Pyrolysis stands out as one potential route for valorizing abundant agro-industrial cocoa residues. However, the products of this reaction, particularly bio-oil, do not possess the required quality for direct use in many applications. Thus, this study explores the use of iron sulfate and zinc sulfate as potential catalysts in the pyrolysis of these residues. In this investigation, the biomass, previously ground and dried, was impregnated with varying percentages of ferric sulfate and zinc sulfate. The TG-FTIR technique was employed to ascertain the effect of these salts on the pyrolysis of cocoa shell. The results were fitted with the DAEM model with three pseudo-components. It was determined that both salts induced alterations in the DTG profiles of the thermal decomposition of cocoa shell. In the evolved gases, compounds such as CO2, H2O, CH4, CO, HCN, and oxygenated compounds like HCOOH and CH3COOH were detected. Ferric sulfate significantly influenced the activation energies governing the reactions of the three pseudo-components. Conversely, the presence of zinc sulfate did not alter the activation energies associated with the decomposition of cocoa shell pseudo-components. Both catalysts induced alterations in the infrared spectra of the evolved gases, which is primarily evident in the relative intensities of bands corresponding to the stretching vibrations of constituent groups within CO2, CO, water, and oxygenated compounds.

A novel magnetic sludge biochar was prepared by making full use of internal iron in sludge combining KMnO4-NaOH modification to enhance the adsorption of Pb (Ⅱ), Cu (Ⅱ) and Cd (Ⅱ)

This study synthesized novel magnetic biochar (PCMN600) by KMnO4-NaOH combined modification using iron-containing pharmaceutical sludge to remove toxic metals from wastewater effectively. Various characterization experiments of engineered biochar showed that the modification process introduced ultrafine MnOx particles on the carbon surface and resulted in higher BET surface area and porosity along with more oxygen-containing surface functional groups. Batch adsorption studies indicated that the maximum adsorption capacities of PCMN600 for Pb2+, Cu2+ and Cd2+ were 181.82 mg/g, 30.03 mg/g and 27.47 mg/g, respectively, at a temperature of 25 °C and pH of 5.0, which were much higher than that of pristine biochar (26.46 mg/g, 6.56 mg/g and 6.40 mg/g). The adsorption datums of three toxic metal ions fitted well to the pseudo-second-order model and Langmuir isotherm, and the sorption mechanisms were identified as electrostatic attraction, ion exchange, surface complexation, cation-π interaction and precipitation. The strong magnetic properties of the engineered biochar endowed the adsorbent with remarkable reusability, and after five cycles of recycling, PCMN600 still retained nearly 80% of its initial adsorption capacities.

A critical review on sustainable hazardous waste management strategies: a step towards a circular economy

Globally, industrialisation and urbanisation have led to the generation of hazardous waste (HW). Sustainable hazardous waste management (HWM) is the need of the hour for a safe, clean, and eco-friendly environment and public health. The prominent waste management strategies should be aligned with circular economic models considering the economy, environment, and efficiency. This review critically discusses HW generation and sustainable management with the strategies of prevention, reduction, recycling, waste-to-energy, advanced treatment technology, and proper disposal. In this regard, the major HW policies, legislations, and international conventions related to HWM are summarised. The global generation and composition of hazardous industrial, household, and e-waste are analysed, along with their environmental and health impacts. The paper critically discusses recently adapted management strategies, waste-to-energy conversion techniques, treatment technologies, and their suitability, advantages, and limitations. A roadmap for future research focused on the components of the circular economy model is proposed, and the waste management challenges are discussed. This review stems to give a holistic and broader picture of global waste generation (from many sources), its effects on public health and the environment, and the need for a sustainable HWM approach towards the circular economy. The in-depth analysis presented in this work will help build cost-effective and eco-sustainable HWM projects.

Green, zero-waste pathway to fabricate supported nanocatalysts and anti-kinetoplastid agents from sugarcane bagasse

The conversion processes of sugarcane into direct-consumption sugar and juice are generating a tremendous amount of waste, the so-called sugarcane bagasse (SCB). Biochar preparation is among the practical solutions aiming to manage and valorize SCB into high added-value functional material (FM). Herein, we propose a novel zero-waste pathway to fabricate two FMs from one biomass. The SCB was first macerated and ultrasonicated to obtain the natural extract that served as bio-reducing medium. Then, the H₂O/EtOH-extracted SCB was in-situ impregnated with a bimetallic solution of copper and silver nitrates. The process produced an intermediate composite (FM₀), Ag/Cu-Ag⁺/Cu²⁺-loaded SCB which was carbonized to elaborate Ag/Cu-Biochar (FM₁), free Ag/Cu nanoparticles (FM₂) were obtained by microwaving the residual liquid waste. FM₁ exhibited high catalytic activity for the total Fenton-like degradation of methylene blue. The experimental data followed the pseudo-first and the pseudo-second order rate laws with apparent degradation rate constants K₁ 45 10^-3 min^-1 and K₂ 0.115 g.mg^-1.min^-1, respectively. FM₀, FM₁ and FM₂ were tested as new anti-kinetoplastid materials against two flagellated protozoans namely the Leishmania spp and the Trypanosoma cruzi. Notably, Ag/Cu (FM₂) showed exceptional leishmanicidal and trypanocidal effects with IC₅₀ values of 2.909 ± 0.051, 3.580 ± 0.016 and 3.020 ± 0.372 ppm for L.donovani, L. amazonensis and Trypanosoma cruzi, respectively. In this way, we combine green chemistry and agrowaste valorization in a full zero-waste process, to address the 3rd (indicator 3.3.5) and 6th (indicator 6.3.1) United Nations sustainable development goals, ″Good Health and Well-Being″ and ″Clean Water and Sanitation″.

Pyrolysis of Biomass Pineapple Residue and Banana Pseudo-Stem: Kinetics, Mechanism and Valorization of Bio-Char

Pineapple residue and banana pseudo-stem are waste from agricultural production in tropical zones, and the characteristics of their pyrolysis should be explored for high-value utilization. Kinetics, thermodynamics, reaction mechanism and valorization of bio-char during pyrolysis of these feedstock were conducted in this study. In biomass mainly decomposed at 150–500 °C, there was a significant mass loss peak for banana pseudo-stem at 650 °C. The activation energy range of pineapple residue and banana pseudo-stem, based on a multi-heating rate method, was 159–335 and 169–364 kJ/mol, respectively. Based on the Gaussian multi-peak fitting method, derivative thermogravimetric curves of pineapple residue and banana pseudo-stem were deconvoluted with three or four fitting peaks, based on the key components in biomass. Interaction between intermediates during pyrolysis increased the complexity of kinetic data. The main carbon number of organic volatiles during pyrolysis was C4 and C5 for pineapple residue, and C2 and C3 for banana pseudo-stem. The high content of cellulose and hemicellulose in biomass improved the yield of volatiles. Porous carbon sourced from pineapple residue and banana pseudo-stems had specific capacitance of 375 F/g and 297 F/g at a current density of 0.5 A/g, respectively. This suggested pineapple residue and banana pseudo-stem as a potential feedstock for electrochemical materials.

Investigation of Synergistic Effects and Kinetics on Co-Pyrolysis of Alternanthera philoxeroides and Waste Tires

A thermogravimetric analysis is used to analyze the thermal kinetics and investigate the synergistic effects between Alternanthera philoxeroides (AP) and waste tires (WTS) in a temperature range of 50-900 °C under three heating rates (15, 25, and 35 °C/min). Two model-free methods (FWO and KAS) and a model-fitting method (CR) were applied to calculate the activation energy. Results revealed that heating rates had no significant effect on the pyrolysis operation. The addition of WTS improved the thermal degradation of the samples as the samples had more than one stage during the main reaction period. A promoting synergistic effect was found in the blend 75A25WT and obtained the lowest activation energy among all the blends without a catalyst, while the blend 50A50WT exhibited an inhibiting effect. On the other hand, the addition of HZSM-5 accelerated the reaction time and obtained the lowest activation energy among all the blends without a catalyst. Furthermore, ΔW of 75A25WT+C was the lowest, indicating that the blend with a catalyst exhibited the strongest synergistic effect. This research confirmed that the addition of WTS improved the thermal parameters of the samples and clarified the capacity of HZSM-5 to reduce the activation energy.

Hydrothermal treatment of metal impregnated biomass for the generation of H2 and nanometal carbon hybrids

The nanocatalyst impregnation onto the biomass matrix has gained importance in enhancing the H₂ yield and overcoming the catalyst deactivation problems. In-situ catalytic gasification of Ru/Fe-impregnated sugarcane bagasse and citrus limetta (mosambi peels) were examined and compared with their raw biomass at subcritical and supercritical water conditions. Bagasse having a higher amount of lignocellulosic content produces a maximum yield of H₂ over moambi peels. Besides, Ru and Fe nano-metal carbon hybrids with crystalline sizes between 10 and 25 nm were formed during in-situ hydrothermal gasification. The performance of hydrothermal gasification based on hydrogen yield was studied, and it relatively follows the order as temperature, nanoparticle composed, metal loading onto biomass matrix, type of catalyst, and biomass used. At the maximum operating temperature of 600 °C, B: W ratio 1:10 for the resident time of 60 min, highest H₂ yield of 12.75 ± 0.17 and 11.20 ± 0.13 mmol/g attained for Ru and Fe impregnated bagasse with the CGE of 72.28 ± 2.17% and 67.08 ± 1.97% respectively. At similar operating conditions, H₂ yields of 8.75 ± 0.18 and 8.13 ± 0.16 mmol/g were achieved with the CGE of 62.4 ± 1.91% and 53.7 ± 1.66% for Ru and Fe impregnated mosambi peels, respectively. Based on the H₂ and CH₄ production, Ru shows the highest performance than Fe catalyst.

Insight into the thermal kinetics and thermodynamics of sulfuric acid plant sludge for efficient recovery of sulfur

The disposal and management of sulfur-rich sludges (SRS) are challenging issues for the industries due to their adverse environmental impact. The present study reports the detailed characterizations and assessment of the thermo-kinetics of sludge generated from the sulfuric acid plant. In addition, the sulfur was retrieved with the help of the evaporation-condensation method. In the active devitalization zone (200-400 °C), a substantial mass loss (91 ± 3%) was observed, primarily due to the vaporization of sulfur. The isoconversional model-free methods were used to appraise kinetic parameters for the pyrolytic process. The average activation energy (64.5 kJ mol^-1) estimated by the Starink method admired the less energy-intensive process and validated the occurrence of thermochemical reactions at low temperatures. The thermodynamic parameters and frequency factor calculated at 10 °C min^-1 were ΔG* = 149.1 kJ mol^-1, ΔH* = 59.8 kJ mol^-1, ΔS* = -0.157 kJ mol^-1K^-1, and A = 2.1 × 10⁵ s^-1. Criado's Z-master plot revealed the dominance of the diffusion mechanism on the process. The efficient recovery of sulfur (≈96% with purity 99 ± 0.5%) was achieved at 440 °C by evaporation-condensation technique, and the findings closely complemented the kinetic and thermodynamic parameters. This study provides a background for a better understanding SRS and efficient sulfur recovery.

Recent advances of thermochemical conversion processes for biorefinery

Lignocellulosic biomass is one of the most promising renewable resources and can replace fossil fuels via various biorefinery processes. Through this study, we addressed and analyzed recent advances in the thermochemical conversion of various lignocellulosic biomasses. We summarized the operation conditions and results related to each thermochemical conversion processes such as pyrolysis (torrefaction), hydrothermal treatment, gasification and combustion. This review indicates that using thermochemical conversion processes in biorefineries is techno-economically feasible, easy, and effective compared with biological processes. The challenges experienced in thermochemical conversion processes are also presented in this study for better understanding the future of thermochemical conversion processes for biorefinery. With the aid of artificial intelligence and machine learning, we can reduce time-consumption and experimental work for bio-oil production and syngas production processes.

Comparative pyrolysis behaviors of stalk, wood and shell biomass: Correlation of cellulose crystallinity and reaction kinetics

In this study, the pyrolysis process of 20 kinds of biomass samples in 3 types (stalk-type, wood-type and shell-type) was investigated with thermogravimetric analyzer, and the correlation of biomass pyrolysis property with biomass chemical structure was put forward. The results showed that the pyrolysis of the 20 kinds of biomass can be classified by types as the pyrolysis of stalk-type biomass had an overlapping decomposition peak of hemicellulose and cellulose at 317 °C. However, the pyrolysis of wood-type and shell-type biomass showed two separated peaks at low temperature and the cellulose peak was higher in wood-type biomass (365 °C) compared to shell-type biomass (348 °C). The different pyrolysis process mentioned above could be due to the positive correlation between cellulose crystallinity and the decomposition temperature of cellulose as well as the activation energy at the decomposition stage of cellulose.