Activated carbon (AC) is widely utilized in water treatment, gas adsorption, and purification as well as the protection of environment due to the characteristics of prominent catalytic and adsorbent effect. The heating performances are therefore of significant importance for the further applications. The main objective of this study was therefore to detail the heating performance of activated carbon in microwave field, and the factors affecting the heating performance were also explored. In this study, the heating performance of AC as affected by microwave power (400, 450, 500, 550, and 600 W), feeding load (5, 10, 15, 20, and 25 g), and reactor volume (50, 100, 150, 200, and 250 mL) were detailed and reported. The results showed that when the microwave powers were 400, 450, 500, 550, and 600 W, the temperatures of AC increased to the desired value (about 200 °C) within 90, 85, 70, 60, and 35 s with average heating rates of 2.0, 2.2, 2.8, 3.0, and 5.9 °C/s, respectively. When the feeding loads were 5, 10, 15, 20, and 25 g, the temperatures of AC increased to desired temperature within 40, 70, 60, 50, and 50 s with average heating rates of 4.2, 2.8, 3.1, 3.50, and 3.55 °C/s, respectively. When the reactor volumes were 50, 100, 150, 200, and 250 mL, the temperatures of AC increased to the desired temperature within 25, 60, 70, 70, and 160 s with average heating rates of 7.6, 3.3, 2.8, 2.6, and 1.2 °C/s, respectively. In general, the faster heating rate of activated carbon was achieved at higher microwave power, more feeding load, and smaller reactor volume. Fitting formulae were given to predict the transient temperatures of AC in the microwave field, and the relative errors were in the ranges of −15.4~12.4%, −15.4~13.5% and −18.7~12.4% at different microwave powers, feeding loads, and reactor volumes, respectively.

Microwave-assisted pyrolysis is an efficient biomass conversion technology that enables uniform and rapid heating for biochar production. In this study, a microwave-assisted pyrolysis system was developed to produce bagasse biochar and examine the effects of pyrolysis temperature and CO₂ flow rate on its surface morphology and structural characteristics. Based on extensive experimental data, response surface methodology (RSM) was applied to establish empirical correlations among microwave energy input, material structural evolution, and the specific surface area and mesopore ratio of biochar. The results revealed that potassium hydroxide (KOH) addition exerted the most influence on the specific surface area, mesopore ratio, and yield of carbon, followed by CO₂ flow rate and pyrolysis temperature. Regression models were subsequently constructed to predict these parameters. Under optimal conditions (pyrolysis temperature: 802.77 °C, KOH addition: 64.5 g, and CO₂ flow rate: 67.81 cm³/min), the specific surface area of carbon reached a maximum value of 1,156.37 m³/g. Under another set of conditions (pyrolysis temperature: 801.53 °C, KOH addition: 70.23 g, and CO₂ flow rate: 71.54 cm³/min), the mesopore ratio of carbon was minimized to 39.29%. These findings provide valuable guidance for the optimization of microwave-assisted synthesis of coconut-shell biochar in subsequent research.

Drying treatment, as a critical initial processing step, enables the transformation of industrial sewage sludge into green fuels, addressing dual environmental and energy challenges. A designed microwave drying thermogravimetric experimental system was developed to investigate the effects of sludge weight (20, 25, 30, 35, and 40 g) and microwave power (400, 450, 500, 550, and 600 W) on the drying performances through analysis of transient temperature and weight. Results identified three distinct drying stages: (I) rapid preheating dominated by sensible heat absorption of free water; (II) constant-temperature stage where microwave energy primarily converted to latent heat for free water removal; (III) slower bound-water removal stage. Crucially, drying performance peaked at 30 g sludge weight. Increasing microwave power significantly enhanced efficiency, reducing total drying time by 37.4% when power rose from 400 W to 600 W. Maximum drying efficiency (81.9 wt.% moisture removal) occurred at 500 W, demonstrating a non-linear power-efficiency relationship. These findings provide essential mechanistic insights and operational parameters to optimize industrial sludge to energy processes.

This study pioneers the application of metal-doped Fe-Al as multifunctional redox catalysts for tunable syngas production from plastics via a microwave-assisted process (CLG). We rationally designed a series of redox catalysts (Ni, Ca, Ce, Sr, Co) to unlock efficient H₂-rich syngas production from (high-density polyethylene) HDPE. A class of metal-doping (Ni, Ca, Ce, Sr, and Co) Fe-Al redox catalysts was engineered, with Ni-doped Fe-Al (Ni-Fe-Al) exhibiting the excellent H₂-rich syngas production (75.32 mmol/gHDPE syngas, 47.09 mmol/gHDPE H₂). This is attributed to the improved redox activity, which facilitates efficient lattice oxygen transfer and catalytic reforming reactions, alongside improved microwave absorption and a porous structure that promotes reactant access. This strategic material design, coupled with process parameter optimization (800 W, redox catalyst/plastic = 2.0), developed a highly efficient HDPE-to-syngas conversion system. The process produced a high-quality syngas (90.03% H₂ + CO, H₂/CO ratio = 2.27) with a rapid heating rate (233.0 °C/min) and minimal energy input (3.52 kWh/molgas). This work provides not just an effective upcycling route for plastics, but a fundamental blueprint for designing advanced redox catalysts to unlock the full potential of microwave-CLG.

In the dual pursuit of achieving the global goal of carbon neutrality and curbing plastic pollution, chemical looping gasification (CLG) technology has emerged a key approach to integrate plastic waste recycling with H2-rich syngas production. This review systematically examines and compares the design strategy (support properties, active metal modification and bimetallic synergy) of oxygen carrier (OC) and the optimization progress of key process parameters (temperature, reactor staging and co-gasification of biomass) in the production of H2-rich syngas from plastic CLG. The findings demonstrate that support optimization and metal synergy can significantly regulate the syngas yield and its H2/CO ratio, while improving the cycle stability of OCs. Temperature and segmented CLG significantly improves the conversion rate and achieve flexible control of the H2/CO ratio. CLG of biomass and plastics can improve the yield and quality of H2-rich synthesis due to the complementary hydrocarbon and the coordinated conversion of tar. However, most studies at present use model plastics as fuel, which highlights the key shortcomings in understanding actual plastic waste, impurities, long-term CLG stability, and systematic economic evaluation. This review aims to provide guidance for the development of stable and selective OC systems and the optimization of CLG systems to achieve sustainable energy conversion of plastic waste.