Adsorption from aqueous phenol and aniline solutions on activated carbons with different surface chemistry

Activated carbons-preparation, characterization and their application in CO2 capture: A review

In this paper, we provide a comprehensive review of the latest research trends in terms of the preparation, and characteristics of activated carbons regarding CO2 adsorption applications, with a special focus on future investigation paths. The reported current research trends are primarily closely related to the synthesis conditions (carbonization and physical or chemical activation process), to develop the microporosity and surface area, which are the most important factors affecting the effectiveness of adsorption. Furthermore, we emphasized the importance of regeneration techniques as a factor determining the actual technological and economic suitability of a given material for CO2 capture application. Consequently, this work provides a summary and potential directions for the development of activated carbons (AC). We attempt to create a thorough theoretical foundation for activated carbons while also focusing on identifying and specific statements of the most relevant ongoing research scope that might be advantageous to progress and pursue in the coming years.

Removal of malachite green from water: Comparison of adsorption in a residue-derived AC versus photocatalytic oxidation with TiO2 and study of the adsorption-photocatalysis synergy

The literature rarely compiles studies devoted to the removal of pollutants in aqueous media comparing adsorption and photocatalytic degradation, and does not pay enough attention to the analysis of combined adsorption-photocatalytic oxidation processes. In the present manuscript, the removal of malachite green (MG) from aqueous solutions has been investigated in three different sustainable scenarios: i) adsorption on activated carbon (AC) derived from a residue, luffa cylindrica, ii) photocatalytic oxidation under simulated solar light using titanium dioxide (TP) and iii) combined adsorption-photocatalytic oxidation using TP-AC (70/30 wt./wt.) under simulated solar light. The study has revealed that in the three scenarios and studied conditions, the total removal of this endocrine-disrupting dye from the solution takes place in the assayed time, 2 h, in some cases just in a few minutes. MG adsorption in the AC is a very fast and efficient removal method. MG photocatalytic oxidation with TP also occurs efficiently, although the oxidized MG is not totally mineralized. MG removal using the TP-AC composite under simulated solar light occurs only slightly faster to the MG adsorption in the AC, being adsorption the dominating MG removal mechanism for TP-AC. Thus, more than 90% of the removed MG with TP-AC under simulated solar light is adsorbed in this carbon-containing composite. The obtained results highlight the interest in adsorption, being the selection of the most suitable removal method dependent on several factors (i.e., the cost of the AC regeneration, for adsorption, or the toxicity of the intermediate oxidation species, for photooxidation). Paying attention to MG photooxidation with TiO2, comparison of two working photodegradation schemes shows that the direct photodegradation of MG from solution, avoiding any initial dark equilibrium period, is more efficient from a time perspective. The use of scavengers has proved that MG photodegradation occurs via an oxidation mechanism dominated by superoxide anion radicals.

Effect of Modification of a Laccase-Based Electrochemical Biosensor with Carbon Nanotubes on Signal Separation of Dihydroxybenzene Isomers

This work describes a new electrochemical biosensor for the simultaneous determination of catechol and hydroquinone. A laccase biorecognition layer was deposited using an innovative soft plasma polymerization technique onto a multiwalled carbon nanotube (MWCNT)-modified glassy carbon electrode (GCE) to sufficiently separate catechol (CT) and hydroquinone (HQ) oxidation peaks. The electrochemical analysis carried out for MWCNTs with various morphologies was supported by density functional theory (DFT) calculations showing differences in the electronic structures of both dihydroxybenzene isomers and the MWCNTs forming the biosensor interlayer. The best biosensor peak separation and biosensor analytical parameters were observed for the device containing 75 μg of MWCNTs with a higher internal diameter. For this laccase-based biosensor, a linearity range from 0.1 to 57 μM for catechol and 0.5 to 57 μM for hydroquinone as well as a sensitivity of 0.56 and 0.54 μA/μM for catechol and hydroquinone was observed, respectively. The limit of detection (LOD) values were 0.028 and 0.15 μM for CT and HQ, respectively. This biosensor was also characterized by good selectivity, stability, and reproducibility. It was successfully applied for the quantification of contaminants in the analysis of natural water samples.

On the use of plastic precursors for preparation of activated carbons and their evaluation in CO2 capture for biogas upgrading: a review

In circular economy, useful plastic materials are kept in circulation as opposed to being landfilled, incinerated, or leaked into the natural environment. Pyrolysis is a chemical recycling technique useful for unrecyclable plastic wastes that produce gas, liquid (oil), and solid (char) products. Although the pyrolysis technique has been extensively studied and there are several installations applying it on the industrial scale, no commercial applications for the solid product have been found yet. In this scenario, the use of plastic-based char for the biogas upgrading may be a sustainable way to transform the solid product of pyrolysis into a particularly beneficial material. This paper reviews the preparation and main parameters of the processes affecting the final textural properties of the plastic-based activated carbons. Moreover, the application of those materials for the CO₂ capture in the processes of biogas upgrading is largely discussed.

A review on production and application of activated carbon from discarded plastics in the context of 'waste treats waste'

In the post-COVID scenario, the annual increase in plastic waste has taken an upsurge due to the disposal of plastic masks, gloves and other protective equipment. To reduce the plastic load ending up in landfills and oceans or dumped at roadsides, the potential of using plastic polymers in different sectors has been investigated over the years leading to their potential application in pavement laying, concrete industry, fuel generation and production of carbon-based compounds among which activated carbons (AC) is a prime example. As one of the most recommended adsorbents for removing contaminants from water and adsorbing greenhouse gases, AC creates a potential sector for using discarded plastic to further treat pollutants and approach closer to a circular economy for plastics. This paper analyses the production process, the effect of production parameters on AC characteristics and properties that aid in adsorption. The interdependence of these factors determines the surface area, porosity, relative micropore and mesopore volume, thereby defining the utility for removing contaminant molecules of a particular size. Furthermore, this work discusses the application of AC along with a summary of the earlier works leading to the existing gaps in the research area. Production costs, formation of by-products including toxic substances and adsorbate selectivity are the major issues that have restricted the commercial application of this process towards its practical use. Research aimed at valorization of plastic waste into ACs would minimize the solid waste burden, along with treating other pollutants.

Diamond in the rough: Polishing waste polyethylene terephthalate into activated carbon for CO2 capture

The scientific community has believed the potential of waste PET plastics as an effective carbon precursor, however, developing PET-derived activated carbons (PETACs) for a specific application is still a challenge we are facing. To overcome the limitation, a whole chain from development method screening to experiments design, finally to sample optimization, for a sample with promising performance, is proposed in this work. By employing PETACs as CO₂ adsorbents, the waste PET plastics, which we believed the "diamond in the rough", have been polished successfully. Therewith the problems of plastic pollution and the greenhouse effect could be simultaneously solved. The first half part of this paper is a mini review: the PETACs development methods were reviewed and the most suitable solution to develop CO₂ adsorbent, i.e., the two-step chemical activation method, was selected. In addition to that, the necessary procedure variables and their value range were determined. In the second half part, the central composite design method was applied for experiments design in which the procedure variables obtained were regarded as the independent indicators (factors here) while the performance indicators, including yield, CO₂ adsorption uptake, and CO₂ over N₂ selectivity, were treated as the dependent indicators (responses here). The responses were obtained through the characterization of the samples developed and statistical analysis could be applied to reveal the relations between the factors and responses. A high-value PETAC, P600K600-1.5, with the highest gas selectivity (22.189) and decent CO₂ adsorption uptake (3.933 mmol/g) was successfully designed.

Investigation of light aromatics removal from industrial wastewater using nano metal organic framework

In this study, the adsorption of benzoic acid and phenols in the aqueous phase by MOF-Cu adsorbent was investigated. A high-performance liquid chromatography (HPLC) device was used to analyze the concentration of contaminants in the solution. Three isotherms, Freundlich, Langmuir, and Temkin were performed for adsorption of Benzoic Acid (BA) and Phenol contaminants. Correlation factor for adsorption isotherms were fitted into Langmuir aqueous BA and Phenol would be 99.89 and 99.98%, respectively. The equilibrium adsorption capacity MOF-Cu of BA and Phenol is 636.73 and 524.42 mg/g, respectively. In this study, high contaminant adsorption with π-π interaction and hydrogen bonding leads to the high capacity of MOFCu. In addition, the increase in adsorption capacity of benzoic acid is due to the electronegative property of oxygen in the carbonyl group and the similarity of the carboxylic acid functional group with the adsorbent. The result shows, that at initial time adsorption, has been a non-linear trend. In addition, the first-order kinetic model is not a suitable option for fitting the experimental data of adsorption kinetics and the adsorption kinetics of BA and Phenol is very well compatible with the semi-second order with the correlation Factor being 99.7 and 99.78, respectively. Also, the equilibrium adsorption capacity in pseudo-second order kinetic for BA and Phenol is 613.5 and 523.56 mg/g respectively.

Adsorption characteristics of rocks and soils, and their potential for mitigating the environmental impact of underground coal gasification technology: A review

This work presents the state-of-the-art review of investigations related to the adsorption process, adsorption models, experimental adsorption results, and influencing factors, considering the main contaminants produced by underground coal gasification (UCG) technology as adsorbates and the various rocks and soils surrounding the UCG cavity as adsorbents. Based on the literature reviewed, it is found that claystone, coal, coal char, shale, and clay materials present a good prospect for effective phenol adsorption; coal, coal char, shale, and clay materials can also remove benzene and some heavy metals from aqueous solutions. However, their performance varies under the effect of the influencing factors, such as the initial concentration of adsorbates in solution, the pH of the solution, the temperature and contact time controlled in the adsorption process, and the adsorbent dosage. A preliminary assessment of the potential of rocks and soils to act as natural buffers in UCG application is provided. The impact of UCG process on the adsorption of contaminants on the surrounding strata together with the major challenges and future perspectives are highlighted and outlined, to identify knowledge deficiencies regarding the retardation of UCG contaminants using the natural buffers. The prospect of surrounding strata as natural buffers can benefit the site selection, design, and commercialization of UCG.

DFT study on the effect of functional groups of carbonaceous surface on ammonium adsorption from water

Density functional theory (DFT) was used to study the adsorption of ammonium ion on carbon materials. The effects of single and multiple adjacent functional groups of carbon structures on ammonium ion adsorption were emphasized. The electrostatic potential, adsorption energy, charge transfer, molecular orbital, and dipole moment of different configurations were analyzed. Results showed that the carbonyl group was more likely to adsorb ammonium ion than lactone, carboxyl, and hydroxyl. When the carbon material contained multiple adjacent functional groups at the same time, the adsorption of ammonium ion can be promoted or inhibited due to the interaction among functional groups. The effect of functional groups on the adsorption of π bond in carbon materials was related to the electronegativity of functional groups, i.e., greater electronegativity led to smaller adsorption energy of π bond. Carbon material itself is nonpolar and hydrophobic, so adding oxygen-containing functional groups can increase the dipole moment of carbon material molecules, thereby enhancing its polarity and adsorption capacity.

Intensification of Dihydroxybenzenes Degradation over Immobilized TiO2 Based Photocatalysts under Simulated Solar Light

The work is focused on the assessment of possible methods for intensification of photocatalytic degradation of common water borne pollutants. Solar photocatalysis poses certain limitations for large scale application with several possible reactor designs which have shown an optimal performance. In the current study, a comparison between two types of pilot scale reactors was made: a flat-plate cascade reactor (FPCR) and tubular reactor with a compound parabolic collector (CPC). Apart from the reactor design, another aspect of possible intensification was a photocatalyst formulation. The efficiency of photocatalytic films that consisted of pure TiO2 nanoparticles was compared to the efficiency of films that consisted of TiO2/CNT composites. Intensification assessment was performed via detailed kinetic modelling, combining the optical properties of films, irradiation conditions and reactor mass balance. Intensification was expressed via intensification indices. Results showed the advantage of the CPC-based reactor design and an unbiased effect of sensitizing agent (CNT) in the photocatalytic film formulation.

Toward Magic Photoacids: Proton Transfer in Concentrated Sulfuric Acid

Photoacids are the most convenient way to deliver protons on demand. So far, their photoacidity allows for studying excited-state proton transfer (ESPT) only to protic or strongly basic solvent molecules. The strongest superphotoacids known so far exhibit excited-state lifetimes of their conjugate base on the order of 100 ps before recapturing the proton again. Here, we describe how we developed a new aminopyrene-based superphotoacid with an excited-state lifetime of its conjugate base of several nanoseconds. It will be shown by fluorescence titration and via Förster cycle that the excited-state acidity is as high as concentrated sulfuric acid and thus exceeding any previous photoacidity by several orders of magnitude. Its outstanding chemical stability and fluorescent properties make it suitable for time-resolved proton-transfer studies in concentrated mineral acids and organic solvents of low basicity.

Degradation pathways of aniline in aqueous solutions during electro-oxidation with BDD electrodes and UV/H2O2 treatment

In this work, it has been studied the mineralization of aniline, a toxic substance of low biodegradability typically found in many industrial wastewaters, through electro-oxidation using boron doped diamond (BDD) electrodes and photo-oxidation (UV photolysis and UV/H₂O₂ treatments). It was observed that in electro-oxidation and UV/H₂O₂, it was feasible to reach aniline mineralizations higher than 85%. Two different degradation routes have been observed during the aniline oxidation in these two treatments. The first route was the mineralization pathway, in which aniline was oxidized to CO₂, water and nitrate. The second route was the polyaniline pathway in which polyanilines of high molecular weight are formed. The intermediate compounds involved in both degradation routes are different depending on the treatment used. In the electro-oxidation, denitrification processes were also observed. From an economical point of view, electro-oxidation of aniline using BDD electrodes is more interesting than UV/H₂O₂ due it has an 87% lower operational cost. So, electro-oxidation using BDD electrodes seems to be a more suitable technique for the mineralization of wastewater containing aniline than UV or H₂O₂ based technologies.

A key parameter on the adsorption of diluted aniline solutions with activated carbons: The surface oxygen content

A total of 11 different commercial activated carbons (AC) with well characterized textural properties and oxygen surface content were tested as adsorbents for the removal of aniline as a target water pollutant. The maximum adsorption capacity of aniline for the studied AC was from 138.9 to 257.9 mg g(-1) at 296.15 K and it was observed to be strongly related to the textural properties of the AC, mainly with the BET surface area and the micropore volume. It was not observed any influence of the oxygen surface content of the AC on the maximum adsorption capacity. However, it was found that at low aniline aqueous concentration, the presence of oxygen surface groups plays a dominant role during the adsorption. A high concentration of oxygen surface groups, mainly carboxylic and phenolic groups, decreases the aniline adsorption regardless of the surface area of the AC.

Self-Powered Electrochemistry for the Oxidation of Organic Molecules by a Cross-Linked Triboelectric Nanogenerator

A cross-linked triboelectric nanogenerator with high performance is designed for the first time, which harvests vibrational energy to self-power the electrochemical oxidation of organic molecules. This system lays the groundwork for applications to an environmentally friendly production of important organic molecules and the waste treatment of organic pollutants.

Removal of 1,2-dichlorobenzene from water emulsion using adsorbent catalysts and its regeneration

Purification of emulsions of 1,2-dichlorobenzene (1,2-DCB) by carbon-based adsorbent catalysts has been studied. The cycle of purification includes: (1) adsorption of 1,2-DCB from the aqueous phase and (II) reductive regeneration by hydrodechlorination of the adsorbed 1,2-DCB by molecular hydrogen in the liquid phase. 1,2-DCB adsorption from aqueous solutions has been found to proceed by the mechanism of volume filling of pores. The rate of hydrodechlorination was shown to correlate with the particle size of the active component: the finer the particles, the higher the activity of the adsorbent catalyst. Pd/FAS with an average Pd particle size of 2.8 nm was found to be the most efficient catalyst.

Kinetic and isotherm studies of adsorption and biosorption processes in the removal of phenolic compounds from aqueous solutions: comparative study

The phenolic compounds are known by their carcinogenicity and high toxicity as well as creating unpleasant taste and odor in water resources. The present study develops a cost-effective technology for the treatment of water contaminated with phenolic compounds, including Phenol (Ph), 2-chlorophenol (2-CP), and 4-chlorophenol (4-CP). So, two sorbents, rice bran ash (RBA) and biomass of brown algae, Cystoseiraindica, were used and results were compared with the commercially granular activated carbon (GAC). The phenolic compounds were determined using a high performance liquid chromatography (HPLC) under batch equilibrium conditions. The effects of contact time, pH, initial adsorbate concentration, and adsorbent dosages on the removal efficiency were studied. The adsorption data were simulated by isotherm and kinetic models. Results indicated that RBA and GAC had the lowest efficiency for the removal of 2-CP, while the order of removal efficiency for C. indica biomass was as follows: 2-CP > 4-CP > phenol. The efficiency of GAC was higher than those of other adsorbents for all of the phenolic compounds. Furthermore, the adsorption capacity of RBA was found to be higher than that of C. indica biomass. The optimal initial pH for the removal of phenol, 2-CP and 4-CP was determined to be 5, 7, and 7 for RBA, GAC, and algal biomass, respectively. Kinetic studies suggested that the pseudo-second order best fitted the kinetic data.

Extraction of sediment-associated polycyclic aromatic hydrocarbons with granular activated carbon

Addition of activated carbon (AC) to sediments has been proposed as a method to reduce ecotoxicological risks of sediment-bound contaminants. The present study explores the effectiveness of granular AC (GAC) in extracting polycyclic aromatic hydrocarbon (PAH) from highly contaminated sediments. Four candidate GAC materials were screened in terms of PAH extraction efficiency using single-step 24-h GAC extractions, with traditional 24-h Tenax extraction as a reference. Subsequently, sorption of native PAHs to the best performing GAC 1240W (0.45-1.70 mm) was studied for sediment only and for GAC-sediment mixtures at different GAC-sediment weight ratios, using 76-µm polyoxymethylene (POM) passive samplers. Granular AC sorption parameters for PAHs were determined by subtracting the contribution of PAH sorption to sediment from PAH sorption to the GAC-sediment mixture. It appears that the binding of PAHs and the effectiveness of GAC to reduce sediment porewater concentrations were highly dependent on the GAC-sediment mixing ratio and hydrophobicity of the PAH. Despite the considerable fouling of GAC by organic matter and oil, 50 to 90% of the most available PAH was extracted by the GAC during a 28-d contact time, at a dose as low as 4%, which also is a feasible dose in field-scale applications aimed at cleaning the sediment by GAC addition and removal.

Effect of the pH in the adsorption and in the immersion enthalpy of monohydroxylated phenols from aqueous solutions on activated carbons

An activated carbon Carbochem--PS230 was modified by chemical and thermal treatment in flow of H(2) in order to evaluate the influence of the activated carbon chemical surface in the adsorption of the monohydroxylated phenols. The solid-solution interaction was determined by analyzing the adsorption isotherms at 298 K at pH 7, 9 and 11 during 48 h. The adsorption capacity of activated carbons increases when the pH solution decreases. The amount adsorbed increases in the reduced carbon at the maximum adsorption pH and decreases in the oxidized carbon. In the sample of granulated activated carbon, CAG, the monohydroxylated phenols adsorption capacity diminishes in the following order catechol >hydroquinone >resorcinol, at the three pH values. The experimental data are evaluated with Freundlich's and Langmuir's models. The immersion enthalpies are determined and increase with the retained amount, ranging between 21.5 and 45.7 J g(-1). In addition, the immersion enthalpies show more interaction with the reduced activated carbon that has lower total acidity contents.

Adsorption of phenol and its derivatives from water using synthetic resins and low-cost natural adsorbents: a review

In this article, the technical feasibility of the use of activated carbon, synthetic resins, and various low-cost natural adsorbents for the removal of phenol and its derivatives from contaminated water has been reviewed. Instead of using commercial activated carbon and synthetic resins, researchers have worked on inexpensive materials such as coal fly ash, sludge, biomass, zeolites, and other adsorbents, which have high adsorption capacity and are locally available. The comparison of their removal performance with that of activated carbon and synthetic resins is presented in this study. From our survey of about 100 papers, low-cost adsorbents have demonstrated outstanding removal capabilities for phenol and its derivatives compared to activated carbons. Adsorbents that stand out for high adsorption capacities are coal-reject, residual coal treated with H3PO4, dried activated sludge, red mud, and cetyltrimethylammonium bromide-modified montmorillonite. Of these synthetic resins, HiSiv 1000 and IRA-420 display high adsorption capacity of phenol and XAD-4 has good adsorption capability for 2-nitrophenol. These polymeric adsorbents are suitable for industrial effluents containing phenol and its derivatives as mentioned previously. It should be noted that the adsorption capacities of the adsorbents presented here vary significantly depending on the characteristics of the individual adsorbent, the extent of chemical modifications, and the concentrations of solutes.

Analyzing a liquid-solid phase countercurrent two- and three-stage adsorption process with the Freundlich equation

Adsorbent consumption advantages of a countercurrent two- and three-stage process are described. The Freundlich equation and equilibrium-stage were used to deduce these adsorption processes; it was proved that large adsorbent savings were obtained from operations of these systems in most cases. Microporous activated carbon was prepared from plum kernels with KOH chemical activation. Isotherm equilibrium adsorptions of three dyes (BB1, MB, and AB74) and three phenols (phenol, 4-CP, and 2,4-DCP) were used to explain both the superior adsorption capability of activated carbon and the advantages of analyzing adsorption system operations with the Freundlich equation, and to calculate the countercurrent two- and three-stage adsorption processes and explain the design procedures. A continuous-flow countercurrent three-stage adsorption process was developed to provide for design in practical application.

Inferring the favorable adsorption level and the concurrent multi-stage process with the Freundlich constant

This paper proposes a method for inferring a favorable level for the adsorption isotherm curve with the Freundlich constant (1/n), explains that a favorable level is only a function of 1/n, and then, five favorable levels are classified according to 1/n value. The adsorbent consumption ratio of the concurrent multi-stage to single-stage system was deduced in order to investigate the relationship between favorable level and the most suitable number of stages. Activated carbon (TGBAC) was prepared from Taiwan Giant Bamboo with steam activation. The isotherm equilibrium of the adsorption of three phenols (phenol, 3-CP, and 4-CP), two dyes (MB and BB 69), and tannic acid on TGBAC was obtained. According to the Freundlich constant (1/n), the adsorption of MB was inferred in a strongly favorable zone. The favorable zone for BB69, phenol, 3-CP, and 4-CP was determined. The tannic acid, the pseudo-linear zone and their most suitable number of stages were also determined. The 1/n values and favorable levels summarized from more than a hundred sources/studies indicate that the favorable levels of the adsorption of dyes and phenols on TGBAC are excellent. This paper proposes a simple method for inferring the favorable level and the most suitable number of stages for the concurrent multi-stage adsorption system.

Effect of activated carbons modification on porosity, surface structure and phenol adsorption

The primary objective of this work was the examination of modified activated carbons with tailored adsorption capacity properties. Production of activated carbons with desired properties was accomplished by modification of surface functional groups and introduction of acidic/basic properties. Modification of an activated carbon was performed using partial oxygen gasification, nitric acid treatment, urea impregnation followed by pyrolysis and pyrolysis in a urea saturated stream. The surface properties of the produced samples were estimated by the multibasic titration method of Boehm and by the CO/CO2 gas evolution profiles, while pore structure development was measured by the N2 and CO2 gas adsorption isotherms. Oxygen gasification resulted in samples with surface area slightly lower that the raw activated carbon; the introduction of surface functional groups depended upon the severity of the treatment: carbonylic and phenolic type groups were introduced in all partially gasified samples, while low temperatures and short reaction times enhanced the basic character of the carbon. However, nitric acid treatment resulted in the introduction of high nitrogen amounts in the samples, the reduction of surface area and the development of a surface containing carboxylic, lactonic, phenolic and carbonylic groups with negligible HCl neutralization capacity. Treatment of activated carbon by urea supported the formation of basic groups and carbonyls. The presence of surface functional groups affected the adsorption capacity of the produced samples for the removal of specific pollutants such as phenols. Urea treated samples with a basic character and high nitrogen content presented the highest phenol uptake capacity; nitric acid treated carbons and oxygen gasified samples presented an acidic surface functionality and a low phenol adsorption capacity. The beneficial role of nitrogen on phenol adsorption was attributed to adsorbate-adsorbent interactions.

Waste materials for activated carbon preparation and its use in aqueous-phase treatment: a review

Commercial activated carbon is a preferred adsorbent for the removal of micropollutants from the aqueous phase; however, its widespread use is restricted due to high associated costs. To decrease treatment costs, attempts have been made to find inexpensive alternative activated carbon (AC) precursors, such as waste materials. Some reviews report the use of waste materials for the preparation of AC; however, these studies are restricted to either type of wastes, preparation procedures, or specific aqueous-phase applications. The present work reviews and evaluates literature dedicated both to the preparation of AC by recycling different types of waste materials and also to its application in various aqueous-phase treatments. It is clear that conventional (from agriculture and wood industry) and non-conventional (from municipal and industrial activities) wastes can be used to prepare AC, that can be applied in various aqueous treatment processes, namely to remove organic pollutants, dyes, volatile organic compounds, and heavy metals. Moreover, high surface areas can be obtained using either physical or chemical activation; however, combined treatments might enhance the surface properties of the adsorbent, therefore increasing its adsorption capacity. It is evident from the revision made that AC prepared from both conventional and non-conventional wastes might effectively compete with the commercial ones. This happens mostly when the activation procedures are optimized considering both the raw material used to produce the carbons and the contaminants to be removed.