Co-pyrolysis kinetics of sewage sludge and bagasse using multiple normal distributed activation energy model (M-DAEM)

Combustion Characterization and Kinetic Analysis of Mixed Sludge and Lignite Combustion

To investigate the feasibility and reaction mechanism of combusting sewage sludge and brown coal in a mixture. Thermal behavior evaluation of combustion characteristics, interactions, and kinetic analysis of sludge-lignite mixture combustion by thermogravimetry (TG). The results showed that the combustion performance of the mixed samples was all in between that of the lignite and sludge samples. The combined combustion index gradually decreased with the increase in sludge mixing. The addition of sludge favors the ignition of the mixture but is not conducive to overall stable combustion. The synergies between the sludges, as assessed by the mass loss curves, are reflected in the ash removal and coke oxidation stages. When the mixture of sludge and lignite is burned at a ratio of 10 wt %, the calorific value can still reach 20.3 MJ/kg, which is only about 4.2% lower than that of burning lignite alone. Application of the kinetic models of FWO, Starink, KAS, and Friedman, in turn, determined a minimum average activation energy of only 132.50 kJ/mol. In addition, the reaction was judged to be a simple complexation reaction by analyzing the thermodynamic parameters (ΔG, ΔS, ΔH, and A), with the combustion process approaching thermodynamic equilibrium and forming stable products. The nucleation model A4.2 can be used as the best reaction mechanism model for sludge-lignite mixed combustion.

Assessment of thermokinetic behaviour of tannery sludge in slow pyrolysis process through artificial neural network

In the leather industry, tannery sludge is produced in large volume. This study investigated the thermal degradation behavior of tannery sludge using thermogravimetric analysis (TGA). The experiments were carried out in an inert atmosphere using nitrogen gas at varied heating rates of 5, 10, 20, and 40 °C/min in the temperature range of 30-900 °C. For the kinetic parameters calculation, three different models, Friedman, Kissinger-Akahira-Sunose (KAS) and the Ozawa-Flynn-Wall (OFW), were employed. The average activation energy E_a obtained from Friedman method, KAS, and the OFW were 130.9 kJ mol^-1, 143.14 kJ mol^-1, and 147.19 kJ mol^-1 respectively. Along with that experiment of pyrolysis was accomplished in fixed bed reactor at temperature of 400 °C. Biochar produced has a yield of about 71%. The analysis of gas chromatography-mass spectroscopy shows the different chemical compounds present in the bio-oil containing hydrocarbons (alkanes and alkenes), oxygen containing compounds (alcohols, aldehyde, ketones, esters carboxylic acids and the esters) and the nitrogen containing compounds. The kinetic assessment was complemented by frequency distribution of activation energy model (DAEM). In the pyrolysis of tannery sludge six pseudo-components were found to be involved. Furthermore, artificial neural network (ANN) was used to predict the activation energy from conversion, temperature, and the heating rate data. MLP-3-11-1 described well the conversion behavior of tannery sludge pyrolysis.

Synergistic interactions between sewage sludge, polypropylene, and high-density polyethylene during co-pyrolysis: An investigation based on iso-conversional model-free methods and master plot analysis

Sewage sludge (SS) is a hazardous by-product of wastewater treatment processes that requires careful management for minimal environmental impacts and effective resource recovery. Through thermochemical processes such as pyrolysis, clean energy is recovered from SS in the form of bio-oil, biogas, and biochar. To improve the yield and quality of products, the co-pyrolysis of more than two materials is increasingly gaining interest. Here, the thermal behaviour, kinetics, and synergistic interactions during the co-pyrolysis of SS with polypropylene (PP) and high-density polyethylene (HDPE) were comparatively evaluated with thermogravimetric analysis at different mixing ratios and heat rates. Activation energies and reaction mechanisms were determined through iso-conversional model-free methods and master plot analysis. Evolved gases were monitored with thermogravimetric-mass spectrometry. Increased volatile conversion and degradation rates, and reduced activation energies during co-pyrolysis were mediated by synergistic interactions between H-radicals of PP/HDPE and oxygenated intermediates of SS. Contrary to the pyrolysis of SS, PP and HDPE, the co-pyrolysis processes are predominantly diffusion-controlled. Insights into the co-pyrolysis processes of SS/PP and SS/HDPE gained from this work provide the theoretical support for subsequent investigation, facilitate design of waste-to-energy reactor, and aid the adoption of the technology to harness the bioenergy potential of the feedstocks.

Possible Sources of Trace Metals in Obese Females Living in Informal Settlements near Industrial Sites around Gauteng, South Africa

Trace metals have been reported in the literature to be associated with obesity. Exposure to some trace metals such as Mn, Cr, Ni, Cd, and Pb may pose a serious health risk to individuals living around a polluted environment. The present study assessed the levels of trace metals in the blood of obese females living around industrial areas in Gauteng, South Africa. The study was carried out using a mixed method approach. Only females with a BMI ≥ 30.0 were considered. A total of 120 obese females participated in the study (site 1: 40-industrial area, site 2: 40-industrial area, and site 3: 40-residential area), aged 18-45 and not in menopause. Blood samples were analysed for trace metals content using inductively coupled plasma mass spectrometry (ICP-MS). The mean concentrations of trace metals were in the order Pb > Mn > Cr > Co > As > Cd (site 1), Pb > Mn > Co > As > Cd (site 2), and Mn > Cr > Co > As > Pb > Cd (site 3). The blood Mn from site 1 ranged from 6.79 µg/L-33.99 µg/L, and the mean differences obtained from the participants from different sites were significant (p < 0.01). The blood levels of Mn, Pb, Cr, Co, As, and Cd were above the recommended limits set by the WHO in some of the participants. The present study noted, among others, closeness to industrial areas, lifestyle decisions such as the use of tobacco products by their partners indoors, and the method used for cooking as factors that might have accounted for the blood levels of Mn, Pb, Cd and Co. The study showed that there is a need for constant monitoring of the levels of trace metals in the blood of those living in these areas.

Co-pyrolysis technology for enhancing the functionality of sewage sludge biochar and immobilizing heavy metals

Sewage sludge (SS) is a frequent and challenging issue for countries with big populations, due to its massive output, significant hazard potential, and challenging resource utilization. Pyrolysis can simultaneously realize the reduction, harmlessness and recycling of SS. Co-pyrolysis offers a wide range of potential in terms of increasing product quality and immobilizing heavy metals (HMs), thanks to its capacity to use additives to address the mismatch between SS characteristics and pyrolysis. High-value utilization potential of SS biochar is the key to evaluating the advancement of treatment technology. A further requirement for using biochar resources is the immobilization and bioavailability reduction of HMs. Due to the catalytic and synergistic effects in the co-pyrolysis process, co-pyrolysis SS biochar exhibits enhanced functionality and has been applied in soil improvement, pollutant adsorption and catalytic reactions. This review focuses on the research progress of different additives in improving the functionality of biochar and influencing the behavior of HMs. The key limitation and challenges in SS co-pyrolysis are then discussed. Future research prospects are detailed from seven perspectives, including pyrolysis process optimization, co-pyrolysis additive selection, catalytic mechanism research of process and product, biochar performance improvement and application field expansion, cooperative immobilization of HMs, and life cycle assessment. This review will offer recommendations and direction for future research paths, while also assist pertinent researchers in swiftly understanding the current state of SS pyrolysis research field.

Recent Progress in Sludge Co-Pyrolysis Technology

With the development of society and industry, the treatment and disposal of sludge have become a challenge for environmental protection. Co-pyrolysis is considered a sustainable technology to optimize the pyrolysis process and improve the quality and performance of pyrolysis products. Researchers have investigated the sludge co-pyrolysis process of sludge with other wastes, such as biomass, coal, and domestic waste, in laboratories. Co-pyrolysis technology has reduced pyrolysis energy consumption and improved the range and quality of pyrolysis product applications. In this paper, the various types of sludge and the factors influencing co-pyrolysis technology have been classified and summarized. Simultaneously, some reported studies have been conducted to investigate the co-pyrolysis characteristics of sludge with other wastes, such as biomass, coal, and domestic waste. In addition, the research on and development of sludge co-pyrolysis are expected to provide theoretical support for the development of sludge co-pyrolysis technology. However, the technological maturity of sludge pyrolysis and co-pyrolysis is far and needs further study to achieve industrial applications.

Thermal Debinding Kinetics of Gelcast Ceramic Parts via a Modified Independent Parallel Reaction Model in Comparison with the Multiple Normally Distributed Activation Energy Model

This work aims to provide useful insights into the thermal debinding kinetics of gelcast ceramic parts, especially for debinding kinetics prediction involving heat preservation. Debinding experiments were conducted in a differential thermogravimetric analyzer at five heating rates (5, 8, 10, 15, and 20 °C/min) in the temperature range of 35-900 °C under an air atmosphere. The conversion (α) and pyrolysis rate (dα/dT) data were simulated using a modified independent parallel reaction (IPR) model and a multiple normally distributed activation energy model (M-DAEM). Their validity was assessed and compared by checking the agreement between the experimental results and the prediction capability. The results showed that both the modified IPR model and M-DAEM had high predictability for thermal debinding kinetics under linear heating conditions. The fitting quality parameters (Fit) were less than 1.406 and 1.01%, respectively. The activation energies (E _i , i = 1, 2, 3, 4, and 5) calculated by the M-DAEM ranged from 153.312 to 217.171 kJ/mol. The relationships between E _i of pseudo components 1 to 5 calculated by the modified IPR model were a function of the conversion rate. The E _i values were E ₁(α) = 116.750 + 11.153α - 26.772α² + 4.362α³ kJ/mol, E ₂(α) = 139.595 - 66.162α + 75.702α² - 38.041α³ kJ/mol, E ₃(α) = 190.854 + 135.755α - 214.801α² + 116.093α³ kJ/mol, E ₄(α) = 64.068 + 280.086α - 380.270α² + 264.724α³ kJ/mol, and E ₅(α) = 188.257 - 77.086α + 74.129α² - 48.669α³ kJ/mol, respectively. However, it is noteworthy that the α and dα/dT curves predicted by the modified IPR model with a deviation of less than 8% were better than those predicted by the M-DAEM for the linear thermal debinding process with the holding stage. Accordingly, it is believed that the proposed modified IPR model is suitable for describing the thermal debinding kinetics involving the heat preservation of gelcast green parts.

Tailoring biochar for persulfate-based environmental catalysis: Impact of biomass feedstocks

Biochar, a carbonaceous material with engineering potential, has gained attention as an efficient catalyst in persulfate-based advanced oxidation processes (PS-AOPs). Although biomass feedstocks are known as a critical factor for the performance of biochar, the relationship between the catalytic efficiency/mechanism and the types of biomass feedstocks is still unclear. Thus, according to recent advances in experimental and theoretical researches, this paper provides a systematic review of the properties of biochar, and the relationship between catalytic performance in PS-AOPs and biomass feedstocks, where the differences in physicochemical properties (surface properties, pore structure, etc.) and activation path of different sourced biochars, are introduced. In addition, how the tailoring of biochar (such as heteroatomic doping and co-pyrolysis of biomass) affects its activation efficiency and mechanism in PS-AOPs is summarized. Finally, the suitable application scenarios or systems of different sourced biochars, appropriate methods to improve the catalytic performance of different types of biochar and the prospects and challenges for the development of biochar in PS-AOPs are proposed.

Optimization of primary sewage sludge and coal lignite by microwave-assisted pyrolysis for the production of bio-oil

In the present study, the raw materials and produced bio-oil were characterized in terms of physical and chemical properties. Response surface methodology (RSM) based on central composite was used to investigate the process parameter significance on bio-oil yield. The statistical significance is indicated by P-value of less than 0.05 at 95% confidence level. For raw material, coal lignite spectrum showed potential existence of phenols, alcohol and water linked to mineral water associated with the hydroxyl group found in stretching vibrations that are between 3200 and 3400 cm^-1. The oxygen-containing groups such as C = O, C-O and aromatic skeletal lignin from lignocellulosic materials were observed on the coal lignite spectrum. Sewage sludge spectrum showed the presence of amide I, amide II, aliphatic methylene, lipids and fats. Si-O of clay minerals and silicates impurities were attributed by peaks 872 and 1031 cm^-1 on the primary sewage sludge spectrum, respectively. The produced bio-oil results from Gas chromatography-Mass spectrometry (GC-MS) were in agreement with Nuclear magnetic resonance (NMR) and Fourier-transform infrared (FTIR) spectroscopy results. Maximum bio-oil of 42 wt% was obtained under the following conditions : temperature, 550°C, heating rate, 180.3°C/min and particle size 425 µm.

Enhanced removal of ibuprofen by heterogeneous photo-Fenton-like process over sludge-based Fe3O4-MnO2 catalysts

Heterogeneous photo-Fenton-like catalysts with low cost, little hazard, high effectiveness and facile separation from aqueous solution were highly desirable. In this study, sludge-based catalysts combining nano Fe₃O₄-MnO₂ and sludge activated carbon were successfully synthesized by high-temperature calcination method and then characterized. These synthetic materials were applied to remove ibuprofen in the heterogeneous photo-Fenton process. The preparation conditions of sludge-based catalysts optimized by orthogonal experiments were 2.0 M of ZnCl₂, a temperature of 500 °C, a pyrolysis time of 60 min, and a sludge ratio: Fe₃O₄-MnO₂ of 25:2. In batch experiments, the optimal experimental conditions were determined as catalyst dosage of 0.4 g·L^-1, hydrogen peroxide concentration of 3.0 mL·L^-1, pH value of 3.3, and contact time of 2.5 h. The degradation rate sludge/Fe₃O₄-MnO₂ catalyst to ibuprofen is up to 95%. The removal process of ibuprofen fitted the pseudo-second-order kinetic model, and the photocatalytic degradation process was the main factor controlling the reaction rate. The catalytic mechanism was proposed according to the Fourier transform infrared analysis and mass spectrometry product analysis; it was mainly attributed to the interaction between hydroxyl groups and benzene rings.

A validated Distributed Activation Energy Model (DAEM) to predict the chemical degradation of biomass as a function of hydrothermal treatment conditions

This study proposes a DAEM (Distributed Activation Energy Model) approach to predict the chemical alterations of lignocellulosic biomass as a function of hydrothermal treatment conditions. The model is first tuned by an original device allowing the sample shrinkage to be continuously assessed during hydrothermal treatment in saturated water vapor up to 190 °C. The shrinkage dynamic is supplied in the DAEM model as an indicator of the degree of biomass conversion. A set of chemical analyses was performed at selected residence times and treatment temperatures to correlate this degree of conversion with the resulting chemical molecules. A set of functions was then derived from this database to correlate the degree of conversion with the components concentrations. Finally, a validation database was built with different combinations of temperature levels and residence times. The model was proved to be predictive on this new dataset.

Multi-distribution activation energy model on slow pyrolysis of cellulose and lignin in TGA/DSC

Developing a kinetic model to analyze the multi-step reaction of biomass pyrolysis is pivotal to elucidate the mechanism of the pyrolysis. For this purpose, a model-fitting method such as multi-distribution the Distributed Activation Energy Model (DAEM) is one of the most reliable methods. DAEM with 4 different distribution functions of Gaussian, Logarithmic, Gumbel, and Cauchy was utilized to characterize the pyrolysis of cellulose and lignin during Thermogravimetric Analysis/Differential Scanning Calorimetry (TGA/DSC) instrumentation. By comparing Derivative Thermogravimetry (DTG) and DSC profiles, determination of pseudo-components can be done more accurately. A kinetics analysis on the pyrolysis of cellulose with a single Gaussian distribution DAEM yielded a single activation energy of 178 kJ mol⁻¹ with a narrow standard deviation. This result was justified by a single and dominant endothermic peak followed by minor exothermic peaks in the DSC result. For lignin pyrolysis, the presence of multiple peaks is characterized by four pseudo-components in DAEM with activation energies of 157, 174, 194, and 200 kJ mol⁻¹. These pseudo-components were confirmed by the DSC result which indicated the occurrences of two exothermic peaks with two lesser exothermic or possibly endothermic peaks at the same temperature range. These findings imply the importance of DSC to support a kinetics study of thermogravimetric pyrolysis.

Application of sectionalized single-step reaction approach (SSRA) and distributed activation energy model (DAEM) on the pyrolysis kinetics model of upstream oily sludge: Construction procedure and data reproducibility comparison

As the dominant hazardous waste discharged from petroleum industry, the pyrolysis features of the upstream oily sludge (UOS) were scrutinized by way of TGA/DSC. The pyrolysis kinetics model of UOS was systematically constructed by sectionalized single-step reaction approach (SSRA) and distributed activation energy model (DAEM), and the data reproducibility was further evaluated. The results showed that when the pyrolysis operation temperature interval was set from 380 K to 1170 K, two weigh loss step, two endo/exothermic regions and three significant mass-loss peak were respectively emerged in TG, DSC and DTG curves, based on which the TG curves could be sectionalized into three stages. Attributing to the ∆E/E_α¯ value of each stage was higher than 10% but lower than 20% derived from the activation energy assessment, it is not only revealed three multi-step reactions were carried out in sequence with an individual dominant single-step reaction which was sufficient for the SSRA utilization, but also displayed a well fitted by the Gaussian distribution which satisfied the requirement of DAEM implementation. Based on the five-step construction procedure introduced in this paper, pyrolysis kinetics model of UOS could be successful established and interpret as SSRA-based and DAEM-based piecewise function. The latter exhibited a better performance on the data reproduction than the former because the nRSS value of the reproduced data derived from DAEM-based model was lower than 1.86%. The higher mathematical flexibility of DAEM-based model function was the major attribution to a better data reproducibility, also, it possessed a potential ability in predicting the reaction rate at an arbitrary reaction temperature once the heating ratio was preset.

Comparison of adsorption behavior studies of methylene blue by microalga residue and its biochars produced at different pyrolytic temperatures

The adsorption behaviors of methylene blue (MB) on microalga residue powder (MRP) and biochars derived from microalga residue (MRB) produced at different pyrolytic temperatures were compared. Six biochars were prepared from residual Chlorella sp. and Spirulina sp. at different pyrolytic temperatures in the range of 200-550 °C. The adsorption kinetics, isotherms, thermodynamics, and the effect of pH were studied, and chemical analyses of MB-loaded MRP and MRB were conducted using SEM, FTIR, and XPS techniques. The results found that the pseudo-second-order, Elovich, and Freundlich models could effectively describe the MB adsorption process on MRP and MRB. The thermodynamic results confirmed that the adsorption processes were spontaneous and endothermic. Further, MRP showed an excellent adsorption ability on MB through electrostatic interaction, complexation with oxygen/nitrogen-containing functional groups and π-π interaction. However, massive oxygen-containing functional groups after pyrolysis were lost, leading to a significant decrease in the adsorption capacity of MRB on MB. This phenomenon was further observed with increasing pyrolytic temperature. Overall, this study demonstrated that microalga residue performed better for MB removal compared with their pyrolyzed analogs. Graphical abstract.

Investigation on the adsorption of antibiotics from water by metal loaded sewage sludge biochar

Application of sewage sludge biochar as an adsorbent for antibiotics treatment has obtained special attention owning to its low cost and surface functionality. Three metal ions were selected to modify sewage sludge biochar through the pyrolysis with the metal loaded method. Fe loaded sewage sludge biochar (BC-Fe), Al loaded sewage sludge biochar (BC-Al) and Mn loaded sewage sludge biochar (BC-Mn) were characterized and used to explore the performance of adsorbing tetracycline (TC), sulfamethoxazole (SMZ) and amoxicillin (AMC). BC-Fe, BC-Al and BC-Mn possessed rougher surfaces, larger specific surface area and better pore structure. Intra-particle diffusion and Langmuir models were more suitable to describe the adsorption process. The maximum adsorption amount of TC, SMZ and AMC could reach 123.35, 99.01 and 109.89 mg/g by BC-Fe. Furthermore, the main mechanism of antibiotics adsorption by metal loaded sewage sludge biochars might be pores filling, Van der Waals forces and H-bonding. The study can not only solve the problems associated with the pollution of antibiotics from wastewater, but also reduced the treatment pressure of sewage sludge effectively.

Combustion Characteristics, Kinetics, and Thermodynamics of Pine Wood Through Thermogravimetric Analysis

The thermal conversion of woody biomass is increasingly critical for the development of the energy processing technologies and fire safety engineering. The combustion characteristics, kinetics, and thermodynamics of pine wood were characterized through a thermogravimetric analyzer in the air atmosphere. There were two apparent peaks in the derivative TG curves for pine wood. The combustion process of pine wood was divided into two stages. Therein, the first stage occurring in the conversion degree range of 0-0.6 may be considered a one-step reaction. It was easier for pine wood to decompose under air than under nitrogen. Moreover, the first stage of pine wood combustion may be characterized by the diffusion model g(α) = [1 - (1 - α)^1/3]². The kinetic modeling showed a good agreement between the predicted and experimental conversion degree curves. In addition, the high comprehensive combustion index of pine wood at 10 K min^-1 (6.73 × 10^-7 %² min^-2 K^-3) showed its great potential for bioenergy generation. Besides, both the value of ΔH and ΔS exhibited similar patterns with the activation energy value versus conversion degree, while the ΔG value almost remained at a positive constant with conversion degree. The average ΔH, ΔG, and ΔS value was nearly equal under different heating rates.

Developing an all-round combustion kinetics model for nonspherical waste-derived solid fuels

The utilization of challenging solid fuels in the energy industry (especially the ones derived from wastes) has a big priority nowadays, as it is a valid option to keep the recent EU directive related to the decrease of landfills. However, there are serious technical challenges, connecting to the lack of knowledge about the behavior of these fuels in the combustion chamber. This paper discusses the specific aspects of developing particle models concerning the combustion of these non-conventional fuels. A new modeling approach is presented, using which it is possible to develop an all-round particle model that includes every significant influencing process. Moreover, it does not have any restrictions regarding the shape, size and the origin of the particle. As an integral component of this model, the distinctive aspects of intrinsic reaction kinetics related to waste fuels are presented as well.

Study of the Influence of the Almond Shell Variety on the Mechanical Properties of Starch-Based Polymer Biocomposites

This article is focused on the development of a series of biodegradable and eco-friendly biocomposites based on starch polymer (Mater-Bi DI01A) filled with 30 wt% almond shell (AS) of different varieties (Desmayo Rojo, Largueta, Marcona, Mollar, and a commercial mixture of varieties) to study the influence of almond variety in the properties of injected biodegradable parts. The different AS varieties are analysed by means of Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), Scanning Electron Microscopy (SEM), and X-ray Diffraction (XRD). The biocomposites are prepared in a twin-screw extruder and characterized in terms of their mechanical (tensile, flexural, Charpy impact, and hardness tests) and thermal properties (differential scanning calorimetry (DSC) and TGA). Despite observing differences in the chemical composition of the individual varieties with respect to the commercial mixture, the results obtained from the mechanical characterisation of the biocomposites do not present significant differences between the diverse varieties used. From these results, it was concluded that the most recommended option is to work with the commercial mixture of almond shell varieties, as it is easier and cheaper to acquire.

Comparison of Combustion and Pyrolysis Behavior of the Peanut Shells in Air and N2: Kinetics, Thermodynamics and Gas Emissions

The influences of four heating rates on the combustion and pyrolysis behavior in the N2 and air atmosphere were investigated by the Fourier transform infrared spectrometry (FTIR) and thermogravimetric (TG) analysis. the distributed activation energy model (DEAM) and Flynn-Wall-Ozawa (FWO) were used to estimate Ea and A, ΔH, ΔG and ΔS. Experimental results showed that the similar thermal behavior emerged, but the temperatures in the air and N2 atmospheres representing the end of the reaction were about 500 °C and 550 °C, respectively. The results of FTIR showed the peak positions were basically the same, but the concentrations of aromatics, aldehydes and ketones produced by pyrolysis in the N2 atmosphere were higher. When the heating rate was 20 K/min, the comprehensive combustion parameters were 56.442 and 6.871 × 10−7%2/(min2• K3) in the air and N2 atmospheres, respectively, indicating that the peanut shells had great potential to become bioenergy.

Biochar produced from the co-pyrolysis of sewage sludge and walnut shell for ammonium and phosphate adsorption from water

Pyrolysis of sewage sludge to obtain biochar is an environmentally friendly method of sewage sludge utilization. In this study, sewage sludge and walnut shell were co-pyrolyzed to produce biochar, which was utilized in the adsorption of ammonium and phosphate from water. Brunauer-Emmett-Teller analysis, X-ray diffraction spectroscopy, scanning electron microscopy, and Fourier transform infrared techniques were applied to analyze the physical and chemical properties of the biochar. The sewage sludge-based biochar consisted of rich metal oxides and functional groups, and the addition of walnut shell was beneficial for the development of porous structure. When the mixing ratio of sewage sludge and walnut shell was 3:1, the derived biochar (MBC3-1) showed a high adsorption capacity for NH₄⁺ in neutral or weak alkaline water. Pure sewage sludge biochar (SBC) was the best option for the adsorption of PO₄^3- in a wide pH range of water. The adsorption of NH₄⁺ and v on MBC3-1 and SBC were controlled by intraparticle diffusion and pseudo-second-order kinetic models, respectively. Isothermal studies indicated that multiple adsorption processes occurred in the adsorption of NH₄⁺ and PO₄^3-, and the maximum adsorption capacity of NH₄⁺ and PO₄^3- reached 22.85 mg/g and 303.49 mg/g on MBC3-1 and SBC, respectively. Thermodynamic analysis confirmed the exothermic and endothermic nature for NH₄⁺ and PO₄^3- adsorption on biochar, respectively.

Combustion behaviors of pileus and stipe parts of Lentinus edodes using thermogravimetric-mass spectrometry and Fourier transform infrared spectroscopy analyses: Thermal conversion, kinetic, thermodynamic, gas emission and optimization analyses

The combustion behaviors of both Lentinula edodes pileus (LEP) and stipe (LES) were characterized in response to four heating rates in the air atmosphere using thermogravimetric (TG)-mass spectrometry and TG-Fourier transform infrared spectroscopy analyses. There were two and three main peaks of the derivative TG curves for LEP and LES, respectively, with their main combustion stage occurring between 130 and 620 °C. Four iso-conversional models were compared to estimate activation energy values of their combustions. The main emission peaks of most gases ranged from 200 to 350 °C and from 500 to 600 °C for LEP and LES. Their comprehensive combustion parameters at 20 K/min (1.53 and 2.40 × 10^-6 %²/(min²·K³) for LEP and LES, respectively) as well as joint optimizations confirmed their great potential for bioenergy generation. The waste stream of LEP and LES could be well disposed through their combustions with a low level of air pollution.

Thermal debinding behavior of a low-toxic DMAA polymer for gelcast ceramic parts based on TG-FTIR and kinetic modeling

In this work, the pyrolysis characteristics of a low-toxic N,N-dimethylacrylamide (DMAA) gel polymer was investigated through nonisothermal thermogravimetry (TG) and TG-FTIR analyses. Moreover, the thermal debinding kinetics of gelcast SiAlON ceramic parts was studied through three different kinetic models: the Coats–Redfern (C–R) method, distributed activation energy model (DAEM) and three-Gaussian-DAEM-reaction model (3-DAEM). The rationality and adaptability of the three models to the thermal debinding kinetics study were analyzed by comparison with experimental data. The results showed that three mass loss zones were observed in the temperature ranges of 100–320 °C, 320–520 °C and 520–600 °C, respectively, and the main pyrolysis gas products were CO₂, H₂O and CH₄. The conversion rate (α) curves calculated by 3-DAEM were more consistent with the experimental values than those calculated with the C–R and DAEM methods. The fitting quality parameter (Fit%) was less than 2.63%, and the reaction rate (dα/dT) curves calculated by 3-DAEM were bimodal distribution curves, which were in good agreement with the experimental results. The kinetic parameters (E_0,i, k_0,i and σ_i) of the global thermal debinding process calculated by 3-DAEM were 116.00–145.79 kJ mol⁻¹, 1.10 × 10⁹ s⁻¹ and 1.67–43.25 kJ mol⁻¹, respectively. It is anticipated that the study achievements can be used to help predict the thermal debinding behavior and design a reasonable debinding technology for the gelcasting of ceramic parts.

This work successfully extends the distributed activation energy model (DAEM) and the three-Gaussian-DAEM-reaction model to thermal debinding kinetics analysis of gelcast SiAlON green parts.

General distributed activation energy model (G-DAEM) on co-pyrolysis kinetics of bagasse and sewage sludge

In this work, pyrolysis kinetic evolution of mixture of bagasse and sewage sludge with 10%, 30% and 50% (respect to dry initial weight). In terms of kinetic mechanism, the uncertainty of the activation energy obtained by mode-free method was barely known. We found that increasing number of heating rates made result more reliable, but the modeling process more dependent on redundant experiments with extra data. We adapted a novel general distributed activation energy model (G-DAEM) with 5 pseudocomponents for the analysis of kinetic evolution with proposing a more applicable approximation to the general temperature integral. The G-DAEM was trained by data for 20 K/min, and the predictions were performed on data for 15 K/min and 25 K/min. The predictions were well matched to the experimental data. The G-DAEM enhances modeling efficiency of kinetics and provides a effective pathway for high precise model of complicated co-pyrolysis process.