Kinetics evaluation and thermal decomposition characteristics of co-pyrolysis of municipal sewage sludge and hazelnut shell

Co-pyrolysis of sewage sludge and biomass waste into biofuels and biochar: A comprehensive feasibility study using a circular economy approach

Enormous annual sewage sludge (SS) volumes pose global environmental challenges owing to contamination and significant greenhouse gas emissions. Here, we investigated the economic viability of co-pyrolyzing SS and biomass waste to produce biofuels (bio-oil and gas) and biochar. Net present worth (NPW) analysis, the sale product break-even price, and sludge handling price (SHP) were used to determine the profitability of co-pyrolysis compared with SS pyrolysis alone and conventional treatment methods. In this study, the sale prices of biochar based on quality (i.e., stability, carbon sequestration effectiveness, and heavy metal content) were estimated to be 2.24, 1.44, and 0.98 CAD/kg for high-, medium-, and low-grade biochar. The bio-oil prices, estimated based on the higher heating values of bio-oil and diesel, ranged from 0.80 to 1.22 CAD/kg. Sawdust (SD) and wheat straw (WS) were the chosen co-pyrolysis feedstocks, with four mixing ratios (20, 40, 60, and 80 wt%). Economically, SD (40 wt% mixing ratio) co-pyrolysis achieved the best performance, with a maximum NPW of 8.71 million CAD. SD single and co-pyrolysis were the only profitable scenarios. Moreover, SS single pyrolysis and WS co-pyrolysis exhibited higher profitability than conventional SS treatment methods, with SHPs of 65 and 40 CAD/1000 kg dry sludge, respectively. Sensitivity analysis highlighted the dependence of economic performance on biochar and bio-oil market value. This study offers the first economic analysis of this approach and enhances our understanding of the potential of co-pyrolysis for biofuel and biochar production, providing innovative solutions for the environmental challenges of SS disposal.

Recovery of lead and chlorine via thermal co-treatment of municipal solid waste incineration fly ash and lead-rich waste cathode-ray tubes: Analysis of chlorination volatilization mechanism

In this study, a new lead (Pb) and chlorine (Cl) recovery process via the thermal co-treatment of Municipal solid waste (MSW) incineration fly ash (FA) and waste cathode-ray tubes (CRT) was developed and the synergistic effects under different CRT ratios, temperatures, and residence times were comprehensively investigated. Thermogravimetric experiments revealed that the co-processing of FA and CRT exhibited a remarkable synergistic effect as evidenced by the considerable increase in mass loss and mass-loss rate when compared with the theoretical values. When the mixtures with 50% CRT addition was treated at 1200 °C for 60 min, Pb removal rate reached the maximum value of 98.67%, and the Cl removal rate considerably increased by 37.32% compared to that with FA treatment alone. Additionally, the Cl content in the residue was < 2%. It was mainly attributed to the volatilization of chlorides, such as PbCl2, NaCl, and KCl. CaCl2 generated from the decomposition of CaClOH in FA was conducive to improve Pb removal in CRT through indirect chlorination and destroying the glass structure in CRT. Co-processing of FA and CRT demonstrates promising potential for several benefits, including the reduction in melting temperature, recovery of Pb and Cl from secondary fly ash, and the reutilization of calcium-rich slag.

Co-pyrolysis of sewage sludge and waste tobacco stem: Gas products analysis, pyrolysis kinetics, artificial neural network modeling, and synergistic effects

This research comprehensively investigates the co-pyrolysis of sewage sludge (SS) and waste tobacco stem (WTS). Various SS and WTS ratios (1:0, 0.75:0.25, 0.50:0.50, 0.25:0.75, and 0:1) were tested over a range of heating rates (30 °C to 800 °C). Apparent activation energies were calculated using model-free methods, and the co-pyrolysis mechanism was described with the master plot method. Results suggest that SS and WTS co-pyrolysis follows power-law models (P3, P4). Among blends, S75W25 exhibited optimal synergy, with the lowest activation energy required for the pyrolysis reactions and inhibits CO2 emissions. S75W25's pyrolysis gas primarily contained acids (e.g., ethylxanthogenacetic acid, acetic acid), hydrocarbons (e.g., supraene, cyclopropyl carbinol), and other compounds (e.g., CO2, pyrazine, pyridine, indole). ANN was utilized to forecast the temperature-mass loss relationships in co-pyrolysis, with the optimal model being ANN21, yielding a high correlation coefficient (R2 = 0.99999). This study offers guidance for the efficient utilization of waste SS and WTS.

Removal performance and mechanisms of aqueous Cr (VI) by biochar derived from waste hazelnut shell

Cr (VI) is still of great concern due to its high toxicity, solubility, and mobility. The transformation of waste biomass to biochar is favorable for sustainable development. Hazelnut shell, an agriculture waste, was utilized as precursor to prepare biochar at 700 °C and firstly conducted for Cr (VI) removal. Nearly all 50 mg L-1 of Cr (VI) was removed from aqueous media in 180 min under the optimal conditions. The best compliance with pseudo-second-order kinetic model (R2 = 0.999) and Langmuir isotherm model (R2 = 0.999) indicated Cr (VI) removal was a monolayer chemisorption process. The hazelnut shell biochar exhibited superior performance on Cr (VI) removal at low pH (2.0) and Cr (VI) concentrations (≤ 50 mg L-1). Various techniques illustrated that the predominant mechanism of Cr (VI) removal by hazelnut shell biochar involved electrostatic attraction, reduction, and complexation. This study provides a promising low-cost alternative for Cr (VI) elimination from acidic wastewater and groundwater after extraction following by pH adjustment to 2.0.

Thermogravimetric Analysis and Kinetic Modeling of the AAEM-Catalyzed Pyrolysis of Woody Biomass

This work analyzes the catalytic effects induced by alkali and alkaline earth metals (AAEMs) on pyrolysis kinetics. To this end, thermogravimetric analyses (TGA) were carried out with raw beech wood and samples impregnated with NaCl, KCl and MgCl₂ at four heating rates (5, 10, 15 and 30 °C/min). Obtained results showed that AAEM compounds promote the decomposition of biomass by reducing the initial and peak pyrolysis temperatures. More specifically, the catalytic effect of the alkaline earth metal was shown to be stronger than that of alkali metals. To further interpret the obtained trends, a kinetic modeling of measured data was realized using two isoconversional methods (the Ozawa-Flynn-Wall (OFW) and Kissinger-Akahira-Sunose (KAS) models). With a view to identifying a suitable reaction model, model fitting and master plot methods were considered to be coupled with the isoconversional modeling approaches. The 3-D diffusion reaction model has been identified as being well suited to properly simulate the evolution of the conversion degree of each sample as a function of the temperature. Furthermore, the kinetic parameters derived from the present modeling work highlighted significant decreases of the activation energies when impregnating wood with AAEM chlorides, thus corroborating the existence of catalytic effects shifting the decomposition process to lower temperatures. A survey of the speculated pathways allowing to account for the impact of AAEMs on the thermal degradation of woody biomass is eventually proposed to better interpret the trends identified in this work.

Effect of interactions during co-combustion of organic hazardous wastes on thermal characteristics, kinetics, and pollutant emissions

Thermal disposal of organic hazardous wastes (OHWs) in a rotary kiln is an effective method to destroy organic pollutants and reduce the volume, but the complex interactions between various OHWs may result in sharp degradation on combustion performance and the increase in gaseous pollutants emission. Herein, three typical types of OHWs (i.e., pesticide waste, dyeing waste, and organic resin waste, labeled as HW1, HW2, and HW3, respectively) were chosen and thermally co-treated, and the co-combustion characteristics, kinetics, and gas evolutions were systematically studied. A strong positive interaction between HW1 and HW2 was found between 440 and 680 °C possibly due to the catalytic effect of Fe (III) and alkali metals in HW1. The experimental DTG peaks of mixtures at 480 °C were advanced by 60 °C compared with the calculated ones, resulting from the volatiles combustion of HW2 and the catalytic effect from Fe₂O₃ formed during the combustion. The decrease of ignition temperature of mixtures was found helpful for stable combustion, while the decrease of burnout temperature during co-combustion of HW2 and HW3 exhibited the potential to reduce the clinker ignition loss.

Nanoscale zero-valent iron particles supported on sludge-based biochar for the removal of chromium (VI) from aqueous system

Biochar (BC) obtained by the co-pyrolysis of municipal sewage sludge (MSS) and sunflower seed shells (SSS) was utilized to support nanoscale zero-valent iron particles (nZVI) for the synthesis of a composite material (nZVI-BC) for Cr(VI) removal from aqueous systems. A series of characterization methods confirmed successful immobilization of nZVI on the surface of biochar with no aggregation. Batch experiments showed that the initial pH, initial Cr(VI) concentration, and nZVI-BC dose all significantly affected the Cr(VI) removal using nZVI-BC. The kinetics for Cr(VI) removal via nZVI-BC could be better explained by the pseudo-second-order (PSO) adsorption model. Adsorption isotherms analysis demonstrated the superior Cr(VI) removal capability of nZVI-BC in comparison to bare nZVI and BC. nZVI-BC can be reused after the regeneration process by applying 0.1 M H2SO4 and 0.1 M NaBH4 solutions. The reaction mechanism for Cr(VI) removal might involve its chemical reduction on the nZVI-BC surface. Overall, environmentally friendly nZVI-BC was highly efficient in Cr(VI) removal from aqueous systems.

Thermogravimetric pyrolysis of onion skins: Determination of kinetic and thermodynamic parameters for devolatilization stages using the combinations of isoconversional and master plot methods

Thermogravimetric pyrolysis of onions skins was studied thoroughly for the first time. Kinetic calculations of devolatilization stages were performed applying direct Arrhenius plot (DAP) method and combinations of isoconversional and Criado's Z(α) master plot (CZMP) methods. The kinetic parameters calculated using combined methods were utilized successfully to reproduce the experimental kinetic curves whereas those calculated using DAP method failed in this sense. The average E_a values of isoconversional methods were between 164.0 and 172.0 kJ/mol. The CZMP method yielded multiple F-type reaction mechanisms. The simplified kinetic models of combined methods were also developed by using single reaction mechanisms deduced from multiple reaction mechanisms. The Friedman-CZMP combination was the best option for developing simplified/unsimplified kinetic models. Determination of reaction mechanism using DAP method by searching for the highest R² value of regression equation among several candidates was found unreliable. ΔH, ΔG and ΔS values were calculated for 10 °C/min heating rate.

Influence of rice husk addition on phosphorus fractions and heavy metals risk of biochar derived from sewage sludge

This study investigated the effects of rice husk dose and pyrolysis temperature on the phosphorus (P) fractions and environmental risk of heavy metals in biochar co-pyrolyzed from sewage sludge and rice husk. Biochar properties were analyzed, and the transformation of P and heavy metals speciation during co-pyrolysis were also discussed. Co-pyrolysis of raw sludge and rice husk (10-50 wt%) could increase the carbonization degree and stability of biochar at 500 °C. The organic P (OP) in raw sludge (68 wt%) was transformed to inorganic P (IP) during co-pyrolysis, indicating that the addition of rice husk could improve biochar-P bioavailability by promoting the transformation of IP. The IP content increased from 71.5 wt% of sludge biochar to 92 wt% of blended biochar (50 wt% sludge and 50 wt% rice husk) at a pyrolysis temperature of 500 °C. With the mass ratio of sludge to rice husk of 5:5, the OP content decreased from 3 mg g^-1 to 0.75 mg g^-1 as the pyrolysis temperature increased from 300 °C to 700 °C. The ³¹P nuclear magnetic resonance spectra and X-ray photoelectron spectroscopy results showed that P species in biochar mainly existed as orthophosphate, which can be directly taken up by plants. After co-pyrolysis, the toxicity and mobility of heavy metals gradually decreased with increasing rice husk dose and pyrolysis temperature. The study indicates that co-pyrolysis of sewage sludge and rice husk could be a promising P reuse strategy.

Thermodynamics, kinetics and thermal decomposition characteristics of sewage sludge during slow pyrolysis

Pyrolysis has shown great potential for sewage sludge valorisation and management by producing value-added chemicals. Although the product process yields are extensively studied, a few studies exist without consensus on the kinetic properties of sewage sludge pyrolysis. As a result, a study to investigate the thermal decomposition characteristics of Gauteng sewage sludge (GSS) at various heating rates (10, 20, and 30 °C/min), its pyrolysis kinetic parameters, reaction mechanism and thermodynamic properties was meticulously conducted. The results show that sewage sludge decomposition occurs in three stages, whereby the main decomposition (active pyrolysis) takes place at 150-570 °C. Fourier transform infrared spectroscopy (FTIR) analysis results confirm progression of thermal decomposition of GSS and drive off volatile compounds and formation of aromatic structures during TGA studies of GSS. An increase in heating rate shifts the characteristic temperatures towards higher temperatures with the highest decomposition rate of 1.10%/min.mg at 30 °C/min. The activation energies of GSS pyrolysis were calculated using Flynn-Wall-Ozawa, Kissinger-Akahira-Sunose and Starink methods and averaged as 225.92, 218.04 and 218.97 kJ/mol, respectively. GSS pyrolysis involves complex reaction chemistry with high reactivity whereby reactions that follow third order and three-dimensional diffusion-reaction mechanisms dominated the process. However, these mechanisms cannot be used explicitly to define the global pyrolysis kinetics due to the occurrence of multiple simultaneous reactions. The obtained thermodynamic and kinetic data will advance and amplify the design, simulation and optimisation of global energy pyrolysis units for production of value-added chemicals.

Thermogravimetric Study of the Kinetics of the Reaction C + CO2 under Pore-Diffusion Control

This study presents experimental studies of charcoal gasification with CO2 at different heating rates (1, 5, 10, 20, and 50 K min−1). The kinetics of the reaction C + CO2 under pore-diffusion control is studied. We propose a new method for the proper determination of activation energy during the processing of thermogravimetric curves of porous carbon gasification under conditions of pore-diffusion resistance. The results of the inverse kinetic problem solution are compared with different hypotheses about the regime of the investigated heterogeneous reaction process (kinetic, diffusion, pore-diffusion). The change of reaction regimes from kinetic to diffusion is detected during charcoal gasification at different heating rates. At heating rates of 5–20 K min−1, the values of activation energy of carbon gasification reaction in the carbon dioxide atmosphere, obtained by the proposed method, closely match the data found in the previous studies. The use of diffusion models in the processing of thermogravimetric curves determines the conditions under which conventional kinetic models fail to provide adequate information about the temperature dependence of the heterogeneous reaction rate.

Preparation of Porous Biochars by the Co-Pyrolysis of Municipal Sewage Sludge and Hazelnut Shells and the Mechanism of the Nano-Zinc Oxide Composite and Cu(II) Adsorption Kinetics

Municipal sewage sludge (MSS) and hazelnut shells were selected for co-pyrolysis and chemically activated with K2CO3 in a N2 atmosphere. The biochar was then modified by photocatalysis. Hazelnut shells, as a solid waste, were selected as a carbon source additive because of its high cellulose content and similar structure to natural wood. Using hazelnut shells could increase the specific surface area, enhance the porosity, and improve the adsorption capacity of the biochar. Hazelnut shells could also reduce the content of heavy metals in the raw biochar materials, along with increasing the ecological security of biochar and contributing to its further development and utilization. FTIR was used to study the changes in the functional groups on the biochar surface. The layered porous structure of the biochar was observed by SEM. The Cu(II) adsorption capacity of the biochar was 42.28 mg/g after 24 h. The Langmuir and pseudo-second-order models effectively described Cu(II) adsorption.

Stabilization of heavy metals during co-pyrolysis of sewage sludge and excavated waste

In this paper, excavated waste was added to sewage sludge for co-pyrolysis, aiming to stablize the heavy metals in sewage sludge. The effect of co-pyrolysis with various pretreatment (e.g. cooling, drying and hydrothermal pretreatment) on heavy metals stabilization was studied using orthogonal test. The results showed that the optimal conditions are 600 °C, nitrogen flow rate of 200 mL/min, mixing excavated waste with sewage sludge (25:75, wt%) and hydrothermal pretreatment. 90% of the heavy metals in the sewage sludge and excavated waste mixtures were transformed to biochars after co-pyrolysis. Moreover, the state of heavy metals changed from bio-available fractions to stable state, thereby reducing the potential ecological risk index (RI) from 116.8 to below 50, which represented a reduction in contamination levels and ecological risks from considerate to low. Finally, the study found that the synergy between hydrothermal and pyrolysis made full use of the moisture in sewage sludge and was more conducive to the solidification of heavy metals. This paper provides a good option to dispose multiple wastes and reduce their environmental risks.

Effect of potentially toxic metals (PTMs) on the thermal decomposition of phytoremediation plant wastes: Thermokinetic and gas evolution analysis by TG-DTG-MS

Thermal conversion is a promising approach for the disposal of phytoremediation biowastes. The thermal characteristics of potherb mustard biowaste contaminated by potentially toxic metals were studied in this work. Thermogravimetric (TG) and derivative thermogravimetric (DTG) analyses of four feedstocks with different Cd/Zn content were conducted in an inert environment. Evolved gases were identified online by mass spectrometry (MS) coupled with TG. The TG-DTG profiles of the four feedstocks presented similar decomposition stages, whereas the samples with low Cd/Zn had a faster degradation rate, suggesting that the presence of Cd/Zn had little effect on thermal decomposition mechanism. The maximum evolution of H₂ and CH₄ occurred at 500-650 °C, while CO was released at a low temperature. PTMs could catalyze the H₂ production during the pyrolysis of biowaste. This investigation revealed the effects of different Cd/Zn contents on thermal conversion, providing a practical reference for the thermal treatment of phytoremediation biowastes.

Thermogravimetric and kinetic analysis to discern synergy during the co-pyrolysis of microalgae and swine manure digestate

BACKGROUND

Co-pyrolysis of wastes with other feedstock can synergistically improve the rate of biomass decomposition and also help to resolve the issues related to limited availability feedstock. In this regards, synergistic interaction between feedstock during co-pyrolysis is an important aspect of research. As the constituents of aquatic and lignocellulosic biomass are different, and the decomposition pattern of aquatic biomass is dissimilar when compared to lignocellulosic biomass, it is important to understand whether these two biomasses interact during co-pyrolysis.

RESULTS

Synergism in the co-pyrolysis of microalgae (MA), swine manure digestate (SWD), and their blends (MA/SWD) (w/w %), 2.5/7.5 (MD-1), 5/5 (MD-2), and 7.5/2.5 (MD-3), was evaluated based on decomposition behavior, gas yields, extent of thermal degradation, and kinetics. Extractives and volatiles in biomass enhanced the reaction kinetics and products yields, as indicated by the reduction in apparent activation energy of the blends, accompanied by an increase in H2, total gas yield, and extent in degradation. Thermogravimetric data, via isoconversional methods, were interpreted to achieve the apparent activation energies for the thermal degradation of the MA, SWD, and their blends. The best fit reaction models were identified using compensation effect and generalized master plots methods. Semi-quantitative method was used to quantify the evolved gas species. H2, CO, and CO2 were noted to be the dominant gases, implying that tar cracking and reforming reactions were predominant.

CONCLUSIONS

Overall, synergy was noticed with respect to the pyrolysis of SWD biomass to gas products in the presence of MA biomass, whereas synergy was witnessed up to 50 w/w % MA in view of kinetic parameters as evaluation criteria.

Pyrolysis kinetics and thermodynamic parameters of the hydrochars derived from co-hydrothermal carbonization of sawdust and sewage sludge using thermogravimetric analysis

The thermal behavior of the hydrochars from co-hydrothermal carbonization (co-HTC) of sawdust (SD) and sewage sludge (SS) was investigated using thermogravimetric analysis. The comprehensive devolatilization index indicated that the devolatilization performance of SS was decreased by HTC, while it was significantly improved 7.38-23.69 times by co-HTC. The kinetic analysis showed that HTC of SS decreased the average activation energy from 308.96 and 314.78 kJ mol^-1 to 220.86 and 221.27 kJ mol^-1 by Flynn-Wall-Ozawa (FWO) and Kissinger-Akahira-Sunose (KAS), respectively, while it was increased from 182.37 to 207.06 kJ mol^-1 and from 181.06 to 207.05 kJ mol^-1 with the increasing proportion of SD from 25% to 75% during co-HTC, respectively. The thermodynamic parameters revealed that pyrolysis reactivity of the hydrochar derived from SD was improved by co-HTC of SD and SS. Kinetic and thermodynamic findings were useful for the design of pyrolysis process using hydrochar as solid fuel.

Characterizing and optimizing (co-)pyrolysis as a function of different feedstocks, atmospheres, blend ratios, and heating rates

(Co-)pyrolysis behaviors were quantified using TG and Py-GC/MS analyses as a function of the two fuels of sewage sludge (SS) and water hyacinth (WH), five atmospheres, six blend ratios, and three heating rates. Co-pyrolysis performance, gaseous characterizations and optimization analyses were conducted. Relative to N₂ atmosphere, co-pyrolysis was inhibited at low temperatures in CO₂ atmosphere, while the CO₂ atmosphere at high temperatures promoted the vaporization of coke. The main (co-)pyrolysis products of SS and WH were benzene and its derivatives, as well as alkenes and heterocyclic compounds. Average apparent activation energy decreased gradually with the increased atmospheric CO₂ concentration and was highest (377.5 kJ/mol) in N₂ atmosphere and lowest (184.7 kJ/mol) in CO₂ atmosphere. Significant interaction effects on the mean responses of mass loss, derivative TG, and differential scanning calorimetry were found for fuel type by heating rate and atmosphere type by heating rate.

Synergistic effect on co-pyrolysis of rice husk and sewage sludge by thermal behavior, kinetics, thermodynamic parameters and artificial neural network

This study investigates the thermal decomposition, thermodynamic and kinetic behavior of rice-husk (R), sewage sludge (S) and their blends during co-pyrolysis using thermogravimetric analysis at a constant heating rate of 20 °C/min. Coats-Redfern integral method is applied to mass loss data by employing seventeen models of five major reaction mechanisms to calculate the kinetics and thermodynamic parameters. Two temperature regions: I (200-400 °C) and II (400-600 °C) are identified and best fitted with different models. Among all models, diffusion models show high activation energy with higher R²(0.99) of rice husk (66.27-82.77 kJ/mol), sewage sludge (52.01-68.01 kJ/mol) and subsequent blends (45.10-65.81 kJ/mol) for region I and for rice husk (7.31-25.84 kJ/mol), sewage sludge (1.85-16.23 kJ/mol) and blends (4.95-16.32 kJ/mol) for region II, respectively. Thermodynamic parameters are calculated using kinetics data to assess the co-pyrolysis process enthalpy, Gibbs-free energy, and change in entropy. Artificial neural network (ANN) models are developed and employed on co-pyrolysis thermal decomposition data to study the reaction mechanism by calculating Mean Absolute Error (MAE), Root Mean Square Error (RMSE) and coefficient of determination (R²). The co-pyrolysis results from a thermal behavior and kinetics perspective are promising and the process is viable to recover organic materials more efficiently.

The hierarchical porous structure bio-char assessments produced by co-pyrolysis of municipal sewage sludge and hazelnut shell and Cu(II) adsorption kinetics

The co-pyrolysis technology was applied to municipal sewage sludge (MSS) and hazelnut shell with alkaline activating agent K₂CO₃ under N₂ atmosphere. The innovative bio-char produced by co-pyrolysis had significant physical and chemical characteristics. The specific surface area reached 1990.23 m²/g, and the iodine absorption number was 1068.22 mg/g after co-pyrolysis at 850 °C. Although hazelnut shell was a kind of solid waste, it also had abundant cellulose resource, which could contribute to porous structure of bio-char during co-pyrolysis with MSS and decrease total heavy metals contents of raw material to increase security of bio-chars. Meanwhile, the residual fractions of heavy metals in bio-char were above 92.95% after co-pyrolysis at 900 °C except Cd to prevent heavy metals digestion, and the bio-char presented significant immobilization behavior from co-pyrolysis technology. Moreover, the yield and the iodine absorption number of bio-chars under different process variables were analyzed, and it was confirmed that appropriate process variables could contribute the yield and the iodine absorption number of bio-char and prevent to etch pore structure excessively to collapse. The changes of surface functional groups and crystallographic structure before and after co-pyrolysis were analyzed by FTIR and XRD, respectively. The hierarchical porous structure of bio-char was presented by SEM and N₂ adsorption-desorption isotherm. The Cu(II) adsorption capacity of the bio-char was 42.28 mg/g after 24 h, and surface functional groups acted as active binding sites for Cu(II) adsorption. Langmuir model and pseudo-second-order model can describe process of Cu(II) adsorption well.

Recycling of Waste Sludge: Preparation and Application of Sludge-Based Activated Carbon

With the rapidly increasing industrial and agricultural development, a large amount of sludge has been produced from much water treatment. Sludge treatment has become one of the most important environmental issues. Resource utilization of sludge is one of the important efficient methods for solving this issue. Sludge-based activated carbon (SBAC) materials have high adsorption performance and can effectively remove environmental pollutants including typical organic matter and heavy metals through physical and chemical processes. Therefore, developing efficient SBAC materials is important and valuable. At present, preparation, modification, and application of SBAC materials have gained widespread attention. This paper provides a review of the research on SBAC preparation and modification and its utilization in removing environmental pollutants. It included the following topics present in this review: conventional and new methods for preparation of SBAC were clearly present; the effective methods for improving SBAC performance via physical and chemical modification were reviewed; and the correlation of their physic-chemical properties of SBAC with pollutants’ removal efficiencies as well as the removal mechanisms was revealed. SBAC has a better adsorption performance than commercial activated carbon in some aspects. Furthermore, it is a cost-effective technique and has a wide range of raw materials. However, there are still some drawbacks to its research; thus, some suggestions for further research were given in this review.