Characterization Of Activated Carbon Research Articles

Biomass-derived activated carbon nanocomposites with multicolor photoluminescence

In this research work, synthesis, structural, and optical properties of activated carbon (AC) and AC/metal oxide nanocomposites (AC/ZnO and AC/Fe3O4) have been studied. Uniformly distributed metal oxide in AC (AC/ZnO and AC/Fe3O4) nanocomposites were obtained by a single-step impregnation-carbonization method, using bamboo as the biomass precursor, ZnCl2, and FeCl3 as chemical activating agents. The microstructural evolutions and optical characteristics of AC, and the composites have been investigated using X-ray diffraction (XRD), Raman, X-ray photoelectron spectroscopy (XPS), and photoluminescence spectroscopy. Both AC and composites exhibited broad photoluminescence (PL) emissions in the visible region. The PL emissions at 462 and 603 nm by AC were due to the radiative recombination of electron-hole pairs generated by sp2 sites embedded in the sp3 matrix. However, two new emission centers in addition to the above appeared at 520 and 560 nm, in both AC/ZnO and AC/Fe3O4 nanocomposites. The study suggests that metal oxide formation in composites led to a new sp2 cluster formation with a new energy band resulting in two additional emission centers in the green light region. This work provides a simple, cost-effective, and efficient way to develop broadband luminescent materials in visible regions with potential optical and sensing applications.

Improved performance of flow-electrode capacitive mixing through N-doping of activated carbon

Flow electrodes, which are integral to flow-electrode capacitive mixing (F-CapMix), primarily consist of activated carbon (AC), conductive additive and an aqueous electrolyte with a salt. For the better performance of F-CapMix, the AC must have a high surface area and excellent electrical conductivity to facilitate efficient charge percolation and electron transport between the AC particles within the flow electrode. In this study, nitrogen-doped activated carbon (N-doped AC) was synthesized through a straightforward process involving the heating of a mixture of raw AC and melamine in a covered container. The resulting N-doped AC powder exhibited an average of 20 % higher electrical conductivity than raw AC powder without sacrificing the surface area (AC: 2284.7 m2/g vs N-doped AC: 2125.6 m2/g) owing to the incorporation of graphitic nitrogen and oxidized nitrogen into the raw AC surface. The surface characteristics of N-doped AC were found to be similar to those of raw AC. Electrochemical impedance spectroscopy analysis of F-CapMix utilizing N-doped AC in the flow electrode revealed reduced resistance and increased capacitance, leading to an enhancement in power density from 0.706 to 0.828 W/m2. Consequently, integrating N-doped AC into the flow electrode can contribute to the improved performance of F-CapMix.

Polyaniline/activated carbon composite based flowing electrodes for highly efficient water desalination with single-cycle operational mode

Flow-electrode capacitive deionization (FCDI) is a promising technique for water desalination and has received considerable attention. The desalination efficiency of FCDI is significantly influenced by the flowing electrode material. Therefore, it is necessary to develop highly efficient flowing electrode materials to obtain excellent desalination capability. Polyaniline (PANI) is regarded as a promising pseudocapacitive material with high conductivity and desirable hydrophilicity. Herein, in order to improve the stability of PANI, a rod-like polyaniline loaded on activated carbon (AC) was prepared by a simple in-situ polymerization to obtain the PAC composite for FCDI electrode. The composite successfully combined the characteristics of AC and polyaniline. The desalination performance of PAC composite for FCDI single-cycle mode was explored, and the mechanism was ascribed to the synergy between electric-double layer capacitance of AC and pseudocapacitance of PANI. The PAC-9 composite with the best electrochemical performance achieved a salt removal efficiency of 94.3 % and an average salt removal rate of 0.963 μmol cm−2 min−1 at 1.2 V. In addition, the PAC-9 composite did not decay after 12 h of long-term operation, showing that the composite is a promising active material for water desalination.

Recent research progress on modified activated carbon from biomass for the treatment of wastewater: A critical review

AbstractWater is one of the most vital substances on the planet that supports and sustains life. One of the most crucial challenges of our time is water. It is a basic need for all living beings. Worldwide, a large amount of wastewater is produced daily from home and industrial sources, creating problems such a water shortage and environmental degradation. Water that has already been utilized is called wastewater. It has been observed that the wastewater released varies in composition according to the kind of industry and the municipal sources. Microorganisms, heavy metals, organic pollutants, pesticides, phthalates, polycyclic aromatic hydrocarbons, emerging contaminants, and potentially dangerous wastes are all present in it. Among the most effective methods for removing these contaminants in recent times is the adsorption phenomenon. The presence of various contaminants in wastewater can be efficiently reduced by the simple, efficient, and affordable process of adsorption. Selection of suitable adsorbent is the crucial technique in this operation of adsorption. A versatile adsorbent is activated carbon (AC). Their maximum surface reactivity, large surface area, and microporous form are what give them their adsorptive capabilities. To enable recovery and filter, eliminate, or change the toxic components from gases and liquid solutions, they are used to purify, decolorize, deodorize, dechlorinate, separate, and concentrate. As a result, a variety of industries are interested in AC for the process of adsorption. This review paper briefs the characteristics of AC and their preparation techniques. It discusses the numerous approaches for modifying the surface of AC with significant adsorption capability. It also emphasizes the usage of AC with the elimination of different toxins found in waste water.

The Effect of Carbonisation Heating Rates on the Properties of N-Doped Teak Sawdust Waste Activated Carbon

Biomass can be utilised in place of non-renewable raw resources like coal and petroleum residue in the production of activated carbon. Each biomass, however, requires different manufacturing process parameters to obtain the desired activated carbon characteristics due to their different chemical compositions. This study aims to examine the effects of carbonisation heating rates (8°C/min, 10°C/min and 12°C/min) on the characteristics of teak sawdust-derived activated carbon. Furthermore, finding the proper carbonisation heating rate to provide the optimum characteristics is the originality of this study. Activation was carried out at a temperature of 600°C, and simultaneously, 200 mL/min of nitrogen was doped. Thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and adsorption isotherm tests were performed as part of the characterisation. The results revealed that activated carbon carbonised at a rate of 10°C/min produced the best properties. This activated carbon contained 10.8% moisture, 15.26% volatile, 1.73% ash and 72.43% fixed carbon. The majority of the structure is mesopore, with an average pore diameter of 2.43 nm, a pore volume of 0.369 cm3 /g and a specific surface area of 409.698 m2 /g. Its ability to adsorb nitrogen was 239.102 cm3 /g. The successful production of activated carbon from biomass waste derived from teak sawdust offers hope for untapped sawdust waste and has the potential to be used in a number of applications that need adsorption mechanisms.

Advancements in Biomass-Derived Activated Carbon for Sustainable Hydrogen Storage: A Comprehensive Review.

The increasing global energy demand, which is being driven by population growth and urbanization, necessitates the exploration of sustainable energy sources. While traditional energy generation predominantly relies on fossil fuels, it also contributes to alarming CO2 emissions. Hydrogen has emerged as a promising alternative energy carrier with its zero-carbon emission profile. However, effective hydrogen storage remains a challenge. When exposed to hydrogen, conventional metallic vessels, once considered to be the primary hydrogen carriers, are prone to brittleness-induced cracking. This has spurred interest in alternative storage solutions, particularly porous materials like metal-organic frameworks and activated carbon (AC). Among these, biomass-derived AC stands out for its eco-friendly nature, cost-effectiveness, and optimal adsorption properties. This review offers a comprehensive overview of recent advancements in the synthesis, characterization, and hydrogen storage capabilities of AC. The unique benefits of biomass-derived sources are highlighted, as is the pivotal role of chemical and physical activation processes. Furthermore, we identify existing challenges and propose future research directions in AC-based hydrogen storage. This compilation aims to serve as a foundation for potential innovations in sustainable hydrogen storage solutions.

Experimental Studies of Methane Adsorption on Activated Carbon and 3D Graphene Materials

Two kinds of slit pore carbon materials, namely activated carbon (AC) and 3D graphene materials (3D-GS), were purchased to examine their methane storage capabilities. The structural analysis and characterization of AC and 3D-GS were carried out using X-ray diffraction (XRD), scanning electron microscopy (SEM), the X-ray energy dispersive spectrum (EDS), and N2 adsorption/desorption isotherms. Additionally, a thermodynamic framework was employed in the Henry’s law region to evaluate the potential well between the adsorbed fluid and adsorbent. The adsorption behavior of methane on two materials at room temperature and high pressure was also investigated. The results show that the Toth equation is the most suitable model for predicting adsorption isotherms than the Langmuir and L-F equations and determines that the absolute uptake of methane storage on AC and 3D-GS are, respectively, 7.86 mmol·g−1 and 8.9 mmol·g−1 at 298 K and 35 bar. In the Henry’s law region, the isosteric heat of methane adsorption on 3D-GS is larger than that of AC. Meanwhile, the potential well between methane and carbon-based materials decreases as the temperature increases. This indicates that the capacity of methane uptake is enhanced at lower temperatures, which is consistent with the measurements of adsorption isotherms. The research concludes that the 3D-GS is more suitable as a material storage medium than AC. This study provides valuable theoretical guidance for exploring the potential of methane storage on slit pore carbon-based material.

How to Quantify the Adsorption of Cyanuric Acid on Activated Carbon Used from Swimming Pool Disinfection?

The physical and chemical characteristics of an adsorbent are key factors determining its efficiency in relation to a particular adsorbate molecule. The adsorption of cyanuric acid (cya) on activated carbon (AC) has not been extensively explored in terms of its basic phenomenon and specific surface interactions. Cya is an important molecule in the swimming pool industry, as it protects free chlorine from UV light degradation. A proper characterization of AC will be beneficial for swimming pool product suppliers to determine the criteria while purchasing it to remove excess cya accumulated in pools. A detailed investigation of the physicochemical properties of activated carbon was conducted to assess its potential to adsorb cya from water. The effect of the adsorption capacity under various pH conditions was studied and it was found that acidic pH favors the adsorption process. With the help of temperature-programmed desorption coupled with mass spectrometry (TPD-MS) and X-ray photoelectron spectroscopy (XPS), the surface chemistry was well analyzed for a proper understanding of the adsorbent-adsorbate interaction. While conventional pool test equipment gives inconsistent readings of the cya concentration, a UV-vis spectroscopy-based methodology has been developed to accurately measure traces of cya in water. This method can be helpful to validate the accuracy of pool-testers for research and development purposes. The batch adsorption experiments revealed that cya adsorption on activated carbon follows pseudo-second-order kinetics, which confirms that the adsorption mechanism is chemisorption, which in fact, depends highly on the surface chemistry of the AC and the reaction pH.

Performance and dynamic behavior of H2 layered-bed PSA processes using various activated carbons and zeolite LiX for steam methane reforming gas

Layered-bed pressure swing adsorption (PSA) processes using activated carbons (ACs) and zeolite LiX were investigated to elucidate the performance and dynamic behavior of each AC in H2 separation. Experimental adsorption and re-adsorption breakthrough characteristics of ACs (CAC: parent AC, KACa: KOH-activated CAC, and KACi: KOH-impregnated CAC) and zeolite LiX were compared using a steam methane reforming gas. A rigorous dynamic model was used to evaluate the performance of four and six layered-bed PSA processes in terms of purity, recovery, productivity, and impurities. The KACi bed demonstrated the longest breakthrough time of impurities, but its desorption performance was adversely affected by the strong affinity induced by intercalated potassium compounds. While KACa showed higher adsorption capacities than CAC, its slow adsorption rate resulted in the shortest breakthrough time. On the other hand, CAC presented a separation performance between KACi and KACa beds, but its weak CO adsorption affinity led to a relatively wide CO mass transfer zone. Zeolite LiX demonstrated the longest CO breakthrough time, indicating its potential to purify trace CO in the layered-bed, but its layer length must be carefully decided to prevent CO2 propagation. The four layered-bed PSA produced a fuel cell grade H2 (99.9999% purity, 81.54% recovery, 115 mol/kg/day productivity, and < 0.2 ppm CO), which was further improved by the six layered-bed PSA to 1.5% at the same H2 purity. The dynamic behaviors and sensitivity analysis (P/F ratio, adsorption time, AC/LiX ratio, AC type, and number of beds) provide valuable insights and guidelines for the design and optimization of H2 layered-bed PSA.

Adsorptive removal of benzene and toluene from aqueous solutions by oxygen-functionalized multi-walled carbon nanotubes derived from rice husk waste: A comparative study

One of the current directions for sustainable development is to use waste resources to create materials that reduce environmental pollution. In this study, multi-walled carbon nanotubes (MWCNT) and their oxygen-functionalized forms (HNO3/H2SO4-oxidized MWCNT, NaOCl-oxidized MWCNT, and H2O2-oxidized MWCNT) were first synthesized from activated carbon (AC) derived from rice husk waste. A comprehensive comparison of the morphological and structural properties of these materials was conducted using FT-IR, BET, XRD, SEM, TEM, TGA, Raman spectroscopy, and surface charge analysis. The morphology study suggests that the synthesized MWCNTs have an average outer and inner diameter of about 40 and 20 nm, respectively. Additionally, the NaOCl-oxidized MWCNT possesses the largest interspaces between nanotubes, while the HNO3/H2SO4-oxidized CNT has the most oxygen-functional groups, including –COOH, (Ar)-OH, and C–OH. The adsorption capacities of these materials were also compared for the removal of benzene and toluene. Experimental results have shown that while porosity is the primary factor governing the benzene and toluene adsorption onto AC, functionalization degree and surface chemical characteristics are the determining factors in the adsorption capacity of the as-prepared MWCNTs. The adsorption capacity of these aromatic compounds in an aqueous solution increases in the following order: AC < MWCNT < HNO3/H2SO4-oxidized MWCNT < H2O2-oxidized MWCNT < NaOCl-oxidized MWCNT, and in all cases, toluene is more readily adsorbed than benzene under similar adsorption conditions. Wherein the uptake of both pollutants by the prepared adsorbents in this study is best described by the Langmuir isotherm and obeys the pseudo-second-order kinetic model. The adsorption mechanism was discussed in a detailed manner.

Role of grinding method on granular activated carbon characteristics.

A coconut shell (AC1230CX) and a bituminous coal based (F400) granular activated carbon (GAC) were ground with mortar and pestle (MP), a blender, and a bench-scale ball milling unit (BMU). Blender was the most time-efficient for particle size reduction. Four size fractions ranging from 20 × 40 to 200 × 325 were characterized along with the bulk GACs. Compared to bulk GACs, F400 blender and BMU 20 × 40 fractions decreased in specific surface area (SSA, -23% and -31%, respectively) while smaller variations (-14% to 5%) occurred randomly for AC1230CX ground fractions. For F400, the blender and BMU size fraction dependencies were attributed to the combination of (i) radial trends in the F400 particle properties and (ii) importance of shear (outer layer removal) versus shock (particle fracturing) size reduction mechanisms. Compared to bulk GACs, surface oxygen content (At%-O1s) increased up to 34% for the F400 blender and BMU 20 × 40 fractions, whereas all AC1230CX ground fractions, except for the blender 100 × 200 and BMU 60 × 100 and 100 × 200 fractions, showed 25-29% consistent increases. The At%-O1s gain was attributed to (i) radial trends in F400 properties and (ii) oxidization during grinding, both of which supported the shear mechanism of mechanical grinding. Relatively small to insignificant changes in point of zero charge (pHPZC) and crystalline structure showed similar trends with the changes in SSA and At%-O1s. The study findings provide guidance for informed selection of grinding methods based on GAC type and target particle sizes to improve the representativeness of adsorption studies conducted with ground GAC, such as rapid small-scale column tests. When GACs have radial trends in their properties and when the target size fraction only includes larger particle sizes, manual grinding is recommended.

Activation of biomass (cola nut shell) with KOH and K2C2O4: The distinct influence on evolution of volatiles and pore structures of activated carbon

KOH and K2C2O4 are frequently used for activation of biomass to produce activated carbon (AC) but they could impact the evolution of pore characteristics of AC and bio-oil/gas during activation in different ways. This was investigated herein by activation of cola nut shell with KOH or K2C2O4 at 600 to 800 °C. The results indicated that cracking and gasification reactions dominated with presence of either KOH or K2C2O4, diminishing the production of solid products and shifting main products from bio-oil to gases. Nevertheless, KOH was more active than K2C2O4 for cracking of carboxylic acids, furans, nitrogen-containing organics, diminishing their formation in bio-oil while promoting the formation of phenolics from lignin. Additionally, K2C2O4 was more effective than KOH in developing pores at a lower temperature of 600 °C but not at 800 °C (1232.20 cm2g-1 with K2C2O4 versus 1376.0 cm2g-1 with KOH). Nevertheless, K2C2O4 favored formation of macropores, which, however, did not help to enhance the adsorption of phenol. The in-situ IR characterization suggested that KOH or K2C2O4 were highly active to crack -OH and C=O, suppressing their transformation to unsaturated functionalities. Substantial amount of oxygen species could be retained in resulting AC, but mainly in the thermally more stable form of C-O-C bonds for bridging benzene rings.

Получение гранулированного активированного угля из коксовой мелочи Шубаркольского угольного месторождения

The article presents the results of research work on the production of granulated active coal from coke breeze, coal from the Shubarkol deposit. The authors carried out work to determine the binder, the optimal coke/binder weight ratios. The physicochemical characteristics of granular active carbon have been studied. The results of the studies showed that the characteristics of the obtained GAC-Sh based on coke breeze are comparable to those of activated carbon grade AG-3

Effects of Oxygen-Containing Functional Groups on the Electrochemical Performance of Activated Carbon for EDLCs

Activated carbon (AC) is used in commercial electric double-layer capacitors (EDLC) as electrode active material owing to its favorable properties. However, oxygen functional groups (OFGs) present in AC reduce the lifespan of EDLCs. Thus, we investigated the correlation between the OFGs in AC and their electrochemical characteristics. Samples were prepared by heat-treating commercial AC at 300 °C-900 °C for 1 h under two gas atmospheres (N2 and 4% H2/N2 mixed gas). The textural properties were studied, and the reduction characteristics of AC under Ar and H2/Ar mixed gas atmospheres were investigated. Additionally, changes in the OFGs with respect to the heat-treatment conditions were examined via X-ray photoelectron spectroscopy. The specific surface areas of AC-N and AC-H were 2220-2040 and 2220-2090 m2/g, respectively. Importantly, the samples treated in hydrogen gas exhibited a higher yield than those treated in nitrogen while maintaining their pore characteristics. Additionally, the electrochemical performance of the AC was significantly enhanced after the reduction process; the specific capacitance increased from 62.1 F/g to 81.6 F/g (at 0.1 A/g). Thus, heat treatment in hydrogen gas improves the electrochemical performance of EDLCs without destroying the pore characteristics of AC.

Degradation of PAHs in soil by activated persulfate system with activated carbon supported iron-based bimetal

We developed a material of activated carbon (AC)-supported highly active iron-based bimetal (iron–copper bimetal/AC, Fe-Cu/AC) with high efficiency for polycyclic aromatic hydrocarbons (PAHs) degradation in soil by activating persulfate, benefiting from the synergistic effect that the characteristics of AC with porous carbon backbone, multiple active functional groups, high loading capacity and the characteristics of FeCu bimetal with high activity. The addition of Cu to the Fe-based/AC activator not only improved the dispersibility of Fe particles but also maintained the stability of the metal in the Fe-Cu/AC. The thermal activation (50 °C) promoted the degradation of PAHs by the Fe-Cu/AC-activated S2O82− system. Of the various systems tested, the Fe-Cu/AC-activated S2O82− system had the best degradation efficiency for 19 PAHs, with the overall efficiency following the order of Fe-Cu/AC + S2O82− > Fe-Cu + S2O82− > Fe-Cu/AC > S2O82−. The degradation mechanism of the Fe-Cu/AC-activated S2O82− system on soil PAHs showed that OH, OOH, and SO4− were the main active groups involved in the degradation of target PAHs. The target pollutants and their degradation products in the Fe-Cu/AC-activated S2O82− system indicated specific exposure pathways, providing a theoretical basis for the remediation of PAH-contaminated soil.

A Critical Review of the Removal of Radionuclides from Wastewater Employing Activated Carbon as an Adsorbent.

Radionuclide-contaminated water is carcinogenic and poses numerous severe health risks and environmental dangers. The activated carbon (AC)-based adsorption technique has great potential for treating radionuclide-contaminated water due to its simple design, high efficiency, wide pH range, quickness, low cost and environmental friendliness. This critical review first provides a brief overview of the concerned radionuclides with their associated health hazards as well as different removal techniques and their efficacy of removing them. Following this overview, this study summarizes the surface characteristics and adsorption capabilities of AC derived from different biomass precursors. It compares the adsorption performance of AC to other adsorbents, such as zeolite, graphene, carbon nano-tubes and metal-organic frameworks. Furthermore, this study highlights the different factors that influence the physical characteristics of AC and adsorption capacity, including contact time, solution pH, initial concentration of radionuclides, the initial dosage of the adsorbent, and adsorption temperature. The theoretical models of adsorption isotherm and kinetics, along with their fitting parameter values for AC/radionuclide pairs, are also reviewed. Finally, the modification procedures of pristine AC, factors determining AC characteristics and the impact of modifying agents on the adsorption ability of AC are elucidated in this study; therefore, further research and development can be promoted for designing a highly efficient and practical adsorption-based radionuclide removal system.

Enhanced Catalytic Activity of a Coal-Based Powdered Activated Carbon by Thermal Treatment

Thermal treatment is simple and has high potential in activated carbon (AC) modification because its functional groups, structures, and pores can be significantly modified. However, the changes in characteristics of ACs, affecting catalytic activity, have not been investigated enough. Therefore, in this study, a coal-based powdered AC (PAC) was thermally treated, characterized, and subjected to the removal of an antibiotic (oxytetracycline, OTC). The PAC treated at 900 °C (PAC900) showed the best OTC removal compared to the PACs treated under lower temperatures via both adsorption and catalytic oxidation in the presence of peroxymonosulfate (PMS). The results of N2 adsorption/desorption, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, X-ray diffraction, and Boehm titration showed increases in basicity, specific surface area, graphitic structures with higher crystallinity and more defects, and C=O in PAC900 compared to PAC. Stronger signals of DMPO-X and TEMP-1O2 were shown for PAC900+PMS compared to PAC+PMS in electron paramagnetic resonance spectroscopy. It is suggested that a simple thermal treatment can significantly change the characteristics of a PAC, which improves organic micropollutants removal. The changes in the properties, affecting the performance, would provide important information about the improvement of carbonaceous catalysts.

Small particle size activated carbon enhanced flow electrode capacitive deionization desalination performances by reducing the interfacial concentration difference

Flow electrode capacitive deionization (FCDI) has great advantages in high salinity wastewater desalination. However, due to the limited adsorption capacity of electrode material, membrane concentration polarization would form and increase energy consumption, and affect the continuity of desalination. In this work, milling technology was used to modify original activated carbon (AC), the obtained ball milled activated carbon (BAC) was used as FCDI electrode material. The milling process modified multiple physical and electrochemical characteristics of original AC. The highest average salt removal rate (ASRR) of BAC was 2.2 times of that of AC, which was attributed to the modified surface properties including more oxygenated functional group, larger electrostatic gravitation characteristics and better hydrophilicity. The reduced concentration polarization during the desalination was responsible for the increased adsorption capacity, which was due to larger electrolyte contact area, enhanced ions capacity by more suitable pore structures, and 5 times higher energy normalized removal salt (ENRS) of BAC flow electrode than that of AC. Because of its simple operation and remarkable modification effect, ball milling technology shows great potential in large scale modification of electrode materials.

Facile synthesis of mesoporous activated carbons based on ash tree for methylene blue adsorption: Mechanism, kinetics, isotherm, and thermodynamic studies

Activated carbons(AC) were synthesized as a result of chemical activation with ZnCl2, NaOH, H3PO4, and H3BO3 from the ash tree(AH), which is abundant in Turkey and the world. It was investigated that the obtained ACs could be used as effective adsorbents for the removal of methylene blue(MB) from the aqueous solution. SEM, EDX, BET, FTIR, and CHNS elemental analyses were used for the characterization of raw and ACs. The results show that carbonaceous materials contain both mesoporous and active functional groups. The maximum adsorption capacities obtained as a result of chemical activation of ZnCl2 (AH-ZnCl2) and NaOH (AH-NaOH) with the best surface area values were determined as 334 mg g−1 and 364 mg g−1, respectively. The adsorption mechanism was evaluated with pseudo-first-order and pseudo-second-order kinetic models. It can be concluded that ACs prepared from ash wood are quite ideal when compared with different adsorbents in the literature for removing methylene blue from aqueous solutions.

A review on activated carbon modifications for the treatment of wastewater containing anionic dyes

Polluted water resources, particularly those polluted with industrial effluents' dyes, are carcinogenic and hence pose a severe threat to sustainable and longstanding worldwide development. Meanwhile, adsorption is a promising process for polluted/wastewater treatment. In particular, activated carbon (AC) is popular among various wastewater treatment adsorbents, especially in the organic contaminants' remediation in wastewater. Hence, the AC's synthesis from degradable and non-degradable resources, the carbon activation involved in the AC synthesis, and the AC's modification to cutting-edge and effective materials have been modern-research targets in recent years. Likewise, the main research focuses worldwide have been the salient AC characteristics, such as its surface chemistry, porosity, and enhanced surface area. Notably, various modified-AC synthesis methods have been employed to enhance the AC's potential for improved contaminants-removal. Hence, we critically analyze the different modified ACs (with enhanced (surface) functional groups and textural properties) of their capacity to remove different-natured anionic dyes in wastewater. We also discuss the corresponding AC modification techniques, the factors affecting the AC properties, and the modifying agents' influence on the AC's morphological/adsorptive properties. Finally, the AC research of future interest has been proposed by identifying the current AC research gaps, especially related to the AC's application in wastewater treatment.