Performance Of Activated Carbon Research Articles

Characterization of physicochemical properties of activated carbons prepared from penicillin mycelial residues and its adsorption properties for VOCs

In this study, adhering to the concept of "treat waste with waste", the physicochemical properties of activated carbons (ACs) prepared from penicillin mycelial residues (PMR) was characterized, and the adsorption performance of ACs for VOCs was explored. The results showed that AC230–1 exhibited the largest specific surface area (2187.50 m2/g), while AC290–0.5 exhibited the largest microporous surface area (1624.81 m2/g). With the increase of KOH ratio, microporous surface area of ACs decreased gradually, and the pore size distribution of ACs gradually developed to large micropores and mesopores. XRD and Raman results showed that AC290–0.5 had better graphite microcrystalline structure and stability. FT-IR results showed that ACs had similar surface functional groups, and XPS results indicated that AC290–0.5 contained more CO, C-OH, and abundant N-containing functional groups, which could effectively improve the adsorption capacity of ACs for VOCs. AC290–0.5 exhibited the highest dichloromethane (DCM) saturation adsorption capacity (204.83 mg/g), trichloroethylene (TCE) saturation adsorption capacity (732.59 mg/g) and chlorobenzene (CLB) saturation adsorption capacity (735.90 mg/g). The Y–N model could perfectly fit the adsorption breakthrough curve of ACs for VOCs, and adsorption kinetics indicated that the adsorption of ACs for VOCs was mainly physical adsorption. The microporous and surface chemical group of AC were the main factors that determined its adsorption capacity for VOCs.

Shaping metal-organic framework (MOF) with activated carbon and silica powder materials for CO2 capture

Metal-organic framework (MOF) UTSA-16 (Co) was shaped into pellets with diameters of 0.2 mm using activated carbon (AC), silica, and 8% polyvinyl butyral (PVB)/ethanol solution as a binder. A series of AC and silica pellets was prepared with different percentages of the UTSA-16 (Co) MOF. As the percentage of UTSA-16 (Co) increased, the CO2 adsorption capacity and CO2/N2 selectivity of the AC and silica pellets increased. AC/UTSA-16 (Co)− 30% pellets showed 83% enhancement in CO2 adsorption capacity and 800% improvement in CO2/N2 selectivity at 298 K compared to the AC pellet. The stability of AC-UTSA-16 (Co) pellets was analyzed by exposing them to SO2 and NO2 for 2 days. The performance of AC was further investigated by preparing an AC composite pellet using UTSA-16 (Zn). AC/UTSA-16 (Zn)− 30% pellets showed 75% enhancement in CO2 adsorption capacity and 1000% improvement in CO2/N2 selectivity than parent AC pellet. CO2 adsorption–desorption cycles were performed to examine the long-term stability of the pellet composites. The pellets were characterized by scanning electron microscopy (SEM) for particle morphology, thermogravimetric analysis (TGA) for thermal stability, and Brunauer–Emmett–Teller (BET) method for structural properties.

Nipa palm shell as a sustainable precursor for synthesizing high-performance activated carbon: Characterization and application for Hg2+ adsorption

We used for the first time nipa palm shell (NPS) waste as a renewable precursor to synthesize high-porous activated carbon (AC) via direct NaOH activation and investigated its Hg2+ adsorption properties. The characterization results exhibit the successful conversion of NPS into AC with the optimum impregnation weight ratio of NaOH to NPS of 0.5:1, resulting in a large surface area, pore volume, microporosity, and zeta potential of 1214 m2/g, 0.758 cm3/g, 86.4%, and −39.4 mV, respectively. The adsorptive performance of AC towards Hg2+ at 25 °C in a continuous mode was evaluated. High surface area, strongly negative surface charge, and oxygen-containing functional groups of the optimized AC presented a high Hg2+ adsorption capacity (227.86 mg/g). Element composition analysis confirmed the Hg2+ adsorption onto the AC layer. The findings denote the utility and effectiveness of NPS-based AC due to its favorable functional properties and cationic Hg2+ uptake in aqueous media.

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.

Facile Synthesis of NiO-CuO/Activated Carbon Nanocomposites for Use in the Removal of Lead and Cadmium Ions from Water.

In this work, activated carbon (AC) was synthesized and then modified using nickel(II) oxide and copper(II) oxide. Pure-AC, 10, 20, 30, and 40 wt % nanohybrid NiO-CuO/AC nanocomposites (χ-NC/AC NCs) were characterized using XRD, IR, EDS, surface area, and FE-SEM techniques. Furthermore, the adsorbents obtained were tested for their ability to remove hazardous Pb(II) and Cd(II) from water. The fabricated x-NC/AC NC adsorbents showed the highest adsorptive performance toward the adsorption of Pb(II) and Cd(II) from water. The 30-NC/AC NC adsorbent showed the complete removal of Pb(II) at pH = 5 and Cd(II) at pH = 7 within 30 min. Overall, the obtained superior experimental results suggest that the adsorptive performance of AC was greatly enhanced after loading hybrid metal oxide nanoparticles, so its application in water treatment is potential and applicable.

PREPARATION OF ACTIVATED CARBON FROM TIRE DERIVED PYROLYTIC CHAR FOR ADSORPTION OF TETRACYCLINE HYDROCHLORIDE

Effects of activation variables on performance of the obtained activated carbon (AC) were investigated for removal of tetracycline hydrochloride (TCH). Pyrolytic char derived from waste tire was chemically activated via two-step of KOH impregnation following by thermal treatment. According to regression analysis and fitting with second-degree polynomial equation, empirical models were developed to correlate performance of AC in TCH adsorption (percentage removal and adsorption capacity at equilibrium) with three activation variables: impregnation ratio (IR), activation temperature (T) and holding time of thermal treatment (t). The analysis of variance indicated that only T, T2 and IR2 were significant to the prediction of both percentage removal and adsorption capacity. According to the developed models, it is suggested that the pyrolytic char should be activated at IR = 6, T = 750 °C and t = 2 h to obtain the highest efficiency of TCH removal in the tested range of activation condition.

CO2 Adsorption Performance on Surface-Functionalized Activated Carbon Impregnated with Pyrrolidinium-Based Ionic Liquid

The serious environmental issues associated with CO2 emissions have triggered the search for energy efficient processes and CO2 capture technologies to control the amount of gas released into the atmosphere. One of the suitable techniques is CO2 adsorption using functionalized sorbents. In this study, a functionalized activated carbon (AC) material was developed via the wet impregnation technique. The AC was synthesized from a rubber seed shell (RSS) precursor using chemical activation and was later impregnated with different ratios of [bmpy][Tf2N] ionic liquid (IL). The AC was successfully functionalized with IL as confirmed by FTIR and Raman spectroscopy analyses. Incorporation of IL resulted in a reduction in the surface area and total pore volume of the parent adsorbent. Bare AC showed the largest SBET value of 683 m2/g, while AC functionalized with the maximum amount of IL showed 14 m2/g. A comparative analysis of CO2 adsorption data revealed that CO2 adsorption performance of AC is majorly affected by surface area and a pore-clogging effect. Temperature has a positive impact on the CO2 adsorption capacity of functionalized AC due to better dispersion of IL at higher temperatures. The CO2 adsorption capacity of AC (30) increased from 1.124 mmol/g at 25 °C to 1.714 mmol/g at 40 °C.

Focusing on the impact of inherent minerals in coal on activated carbon production and its performance: The role of trace sodium on SO2 and/or NO removal

As a dominant share of coal's alkali metal, sodium has a significant effect on the coal's utilization. To elucidate the effect of sodium in coal on the textural and removal ability of activated carbon (AC), in this research, J/H-XNa-ACs (X is the sodium's contents) were obtained by mixing demineralized Jiangjunmiao (J) or Hongshaquan (H) coal with different concentrations of sodium (0–0.5 wt.%) through liquid impregnation method and followed by carbonization and steam activation. As-prepared ACs' textures and performance were characterized and determined. The results show that: (1) Sodium in coal favors the micropore generation and/or micro- and meso- pore transform into meso- and macro- pore and even collapse. The total BET specific surface area and micropore volume reduced from 741 m2/g and 0.26 cm3/g to 686 m2/g and 0.21 cm3/g of J-XNa-ACs, and 686 m2/g and 0.19 cm3/g to 557 m2/g and 0.17 cm3/g of H-XNa-ACs, respectively. Sodium promotes the increase of the oxygen atoms in carboxyl groups and the carbonyl oxygen of quinone groups of as-prepared ACs. (2) Sodium in coal slightly adjust the sulfur capacity and enhance NO removal obviously. The maximum value of NO conversion is reach 27.1% of J-0.5Na-AC and 47.6% of H-0.5Na-AC, which is higher than 44.9% and 29.7% than J-AC (18.7%) and H-AC (36.7%), respectively. The enhanced mechanism was proposed: sodium enhanced surface chemistry properties and optimized porosity of ACs, which promote the NO and NH3 adsorption, meanwhile, the sodium species in AC could promote the catalytic denitrification activity, and eventually strengthen denitrification. (3) Due to the NO and SO2 competitive adsorption, the lower sulfur capacity and NO conversion were achieved during the SO2 and NO simultaneous removal. This investigation would provide a primary and valuable reference for AC production by utilizing high sodium coal, and further facilitate its practical application.

Rice husk-derived activated carbon electrode in redox-active electrolyte – New approach for enhancing supercapacitor performance

Processing of renewable, abundant, and low-cost biomass into porous carbon materials for application in supercapacitor electrodes has been attracting interest in last years. In this study, activated carbons (ACs) were produced via carbonization of rice husk followed by the chemical activation with KOH. SEM, Raman spectroscopy, XPS, and low temperature nitrogen physisorption were used to characterize the morphology, defectiveness, surface composition and textural parameters of the synthesized ACs. Activation significantly increased the specific surface area of AC up to 2700 m2·g−1 forming a well-developed porous structure favorable for charge accumulation. The electrochemical performance of ACs was tested in the 1 M Na2SO4 and 1 M Na2SO4 + 0.03 M K3Fe[CN]6 electrolytes by cyclic voltammetry, galvanostatic charge – discharge measurements and impedance spectroscopy. The addition of redox-active K3Fe[CN]6 to the conventional 1 M Na2SO4 electrolyte noticeably (in 3.6 times) increased the specific capacitance of the AC-based electrode up to 400 F·g−1 at a current density of 0.5 A·g−1. The high capacitance retentions of 99.6 % in 1 M Na2SO4 and 97.7 % in 1 M Na2SO4 + 0.03 M K3Fe[CN]6 after 5000 charge–discharge cycles, developed microporosity and high electrochemical performance make the rice husk-derived AC a promising electrode material for energy storage applications. At a current density of 0.5 A·g−1 the symmetric AC2-based supercapacitor with the redox-active electrolyte delivered an energy density of 16.7 Wh·kg−1 at power density of 0.4 kW·kg−1.

Performance evaluation and prediction of activated carbon for VOCs via experiments and LFER methods

Due to the diversity and fluidity of volatile organic compounds (VOCs), it is difficult to conduct experimental studies on activated carbon (AC) used to capture VOCs in industry. Therefore, predicting the adsorption capacity of AC for VOCs is of great significance for evaluating the adsorption performance of AC and developing its promising applications. Herein, based on the experimental data of dynamic adsorption, the poly parameter linear free energy relationship (pp-LFER) model was developed to quantify the interactions between VOCs and AC. Through the dynamic adsorption curves of 25 VOCs on a fixed bed packed with the AC, the partition coefficient (PC) and adsorption capacity (q) of AC for VOCs were calculated, and the pp-LFER equations used to predict them were established. For the PC values, the pp-LFER model consists of the excess molar refractive index (E), molar polarizability (S), hydrogen-bond acidity (A), and logarithmic hexadecane-air partition coefficient (L), and the R2 of it was 0.86. For the ln q values, the developed model can predict it in R2 of 0.83, and the increased adsorption capacity was predominantly attributed to the dispersive interaction (lL). Finally, the internal and external validation results confirmed that the developed models have reliability, robustness, and predictability.

Removal of car battery heavy metals from wastewater by activated carbons: a brief review.

Spent automobile batteries are one of the most significant secondary sources of harmful heavy metals for the environment. After being incorporated into the aquatic ecosystems, these metals disseminate to various plants, microorganisms, and the human body and cause multiple adverse effects. Activated carbons (ACs) have long been used as an effective adsorbent for different heavy metals in wastewater treatment processes. Although numerous research works have been published to date on this topic, they are scattered in the literature. In this review, we have assembled these works and provided an extensive overview of the application of ACs for treating spent car battery heavy metals (CBHMs) from aquatic systems. The preparation of ACs from different precursor materials, their application in the adsorption of CBHMs, the adsorption mechanism, kinetics, adsorption isotherms and various parameters that may affect the adsorption processes have been discussed in detail. A brief comparative analysis of the adsorption performances of ACs prepared from different precursor materials is also provided. Finally, recommendations for future research works are also offered.

Copper oxide modified activated carbon for enhanced adsorption performance of siloxane: An experimental and DFT study

CuO is successfully introduced into activated carbon (AC) by a simple impregnation method to improve the adsorption performance of AC on Octamethylcyclotetrasiloxane (D4), and the adsorption mechanism is investigated by combining adsorption experiments and theoretical calculations. Adsorption experiments demonstrate that introducing CuO could significantly enhance the adsorption performance of AC on D4. 10-CuO/AC-800 has the best adsorption performance (495 mg g−1). The density functional theory (DFT) calculations indicate that the adsorption energy of the D4 siloxane molecule on the CuO surface is about −1.40 eV, which is larger than other adsorption sites such as bare AC surface and AC with phenolic hydroxyl groups (AC-OH). In addition, more charge transfer occurs during the adsorption of D4 on the CuO surface, which greatly facilitates the formation of bonds. IGMH analysis proved that D4 siloxane is adsorbed on the CuO surface through CH---Cu hydrogen bond, which is much stronger than the interaction with the bare AC and AC-OH, thus significantly enhancing the adsorption capacity. The present work successfully applies CuO/AC to the adsorption of D4 siloxane, providing a new perspective for improving the treatment of siloxanes by AC.

An Efficient, Multi‐element AC/TiO2/WO3 Photocatalyst for the Degradation of Tetracycline Hydrochloride

AbstractIn this study, a simple one‐step hydrothermal synthesis of three‐element complex system photocatalyst technology is systematically studied. The results show that due to the complex heterojunction formed by titanium dioxide (TiO2), tungsten trioxide (WO3) and activated carbon (AC) and the strong adsorption performance of AC, the catalytic efficiency and cycle stability of the composite have been significantly improved. The excellent electron transport ability of AC is conducive to the separation of carriers, so that the electron transfer between AC/TiO2 and AC/WO3 can make it achieve a heterojunction effect similar to TiO2/WO3. The rich specific surface area of AC and the pores of the “labyrinth” structure can provide a higher concentration of degradable substances inside the catalyst, and the degraded substances are quickly transferred to the active site for degradation. Therefore, by controlling the mass ratio of AC/TiO2/WO3, a photocatalyst with high catalytic efficiency and strong cycle stability was successfully prepared (the degradation efficiency is above 95 %, and the degradation efficiency after 5 cycles is above 80 %).

Formation and availability of methylmercury in mercury-contaminated sediment: effects of activated carbon and biochar amendments

PurposeAs the formation of toxic and bioaccumulative methylmercury (MeHg) in Hg-contaminated sediments is of great concern worldwide, suitable remediation options are needed. Activated carbon (AC) amendment is a contested alternative due to uncertainties surrounding sorption efficiency and its potential role in aiding MeHg formation. The purpose of this study was therefore to demonstrate AC performance under favourable conditions for Hg-methylation and to further understand the role AC plays in the methylation process.Materials and methodsMercury-contaminated sediment (57.1 mg kg−1) was sampled from the Gunneklev fjord, a site known as the most heavily contaminated fjord in Norway. In a laboratory experiment, lignite AC (A-AC, 5%) or activated biochar (A-BC, 5%) along with dried algae biomass, serving as an excess source of easily degradable organic matter (OM) and sulphate, were added to sediment samples that were kept anoxic and dark over a period of 12 months.Results and discussionThe amount of MeHg in sediment and porewater of the amended samples were measured at 0, 1, 3, 6, and 12 months and compared to an unamended control. A net increase of MeHg in the sediment was observed in both control and amended samples, but contrary to expectations, sediment MeHg was 5 and 3 times higher in the A-AC and A-BC treatments, respectively, relative to the control after 12 months. As the stimulation of Hg-methylation could not be attributed to the sorbents supplying more available OM or sulphate for dissimilatory sulphate reduction, it is speculated that the sorbents rather aid this process through shuttling of electrons between the substrates involved. Meanwhile, the A-AC and A-BC amendments strongly reduced the available MeHg-concentration in porewater (by 87% for A-AC and by 93% for A-BC after 12 months), confirming that AC sorbents can be used to effectively limit the transport of MeHg from sediments.ConclusionWhen considering remediation of OM-rich Hg-contaminated sediments with AC, caution is thus warranted, as the overall effect of reducing MeHg-transport out of the sediment could partly be offset by an increased fraction of MeHg in the sediment. Thin-layer capping with AC might therefore be preferable to complete mixing of AC and sediment.

Synergetic effect of N/O functional groups and microstructures of activated carbon on supercapacitor performance by machine learning

Heteroatoms-rich activated carbon (AC) can effectively promote the pseudo-capacitance of AC-based electrodes used in supercapacitors. The well-known microstructural properties of AC immensely contribute to electric double layer (EDL) capacitance. The synergistic role of these multi physio-chemical features of ACs material can enhance the capacitance performance. In this work, Artificial Neural Network (ANN) achieves a superior model to interpret how microstructural features, N/O configurations, and operational parameters influence the EDLCs performance. Multilayer perceptron neural network (MLP-NN) model predicts the in-operando performance of N/O co-doped AC, using electrode materials. The training algorithms in the MLP-NN model show the high feasibility of the model in predicting AC performance with the least error. Among them, the trainbr and trainlm provide the best prediction accuracy. The sensitivity analysis exhibits the maximum effects of microstructural characteristics (<2 nm); and oxidized, pyrolytic of N groups on EDLCs performance by excluding features based on the MLP model. The utilized model presents insights into possible procedures to fabricate the N/O co-doped porous carbon electrodes with maximized specific capacitance. Finally, the genetic algorithm predicts the optimal AC in 6 M KOH at a three-electrode system with a specific capacitance of 550 Fg-1 at 1 Ag-1.

The competing role of moisture in adsorption of gaseous benzene on microporous carbon

The effects of moisture on adsorption of gaseous benzene have been investigated using microporous activated carbon (AC). Here, the performance metrics of an AC bed are explored in terms of the interplay between benzene concentrations (1–20 Pa) and relative humidity (RH, 0–100%). At lower benzene levels (<10 Pa), the adsorption capacity of AC bed was affected sensitively by water vapor with the performance reduction by 27–65% at 100% RH (e.g., relative to 0% RH). In contrast, the negative effect of water on AC performance was not so evident at higher benzene levels (~20 Pa) with only less than 5.3% decrease in the adsorption capacity. A test on the combinatory effects of temperature (25, 40, and 60 °C) and humudity (0 and 100% RH) confirms the relative dominance of temperature over moisture conditions in lowering AC performance. The isotherm analysis of benzene indicates complex fitting results of microporous AC across varying RH levels. The kinetic analysis further demonstrates that the physical nature of benzene is best explained by the pseudo-first order fitting. The test of temperature-swing cycles between adsorption–desorption clarifies the slight decreases in the adsorption capacity (reduction of 11.9% at 0% RH and 3.4% at 50% RH) at lower RH levels, although there is a prominent reduction (35.5%) at the saturated RH. As a whole, the commercial AC product is verified as an excellent adsorbent for purifying the atmosphere from gaseous aromatic pollutants like benzene under dynamically varying environmental conditions (e.g., in the presence of competing component like water vapor at different temperature conditions).

Surface and chemical characteristics of platinum modified activated carbon electrodes and their electrochemical performance.

Platinum (Pt) loaded activated carbons (ACs) were synthesized by the thermal decomposition of platinum (II) acetylacetonate (Pt(acac)2) over chemically activated glucose-based biochar. The effect of Pt loading on surface area, pore characteristics, surface chemistry, chemical structure, and surface morphology were determined by various techniques. XPS studies proved the presence of metallic Pt0 on the AC surface. The graphitization degree of Pt loaded ACs were increased with the loaded Pt0 amount. The electrochemical performance of the Pt-loaded ACs (Pt@AC) was determined not only by the conventional three-electrode system but also by packaged supercapacitors in CR2032 casings. The capacitive performance of Pt@AC electrodes was investigated via cyclic voltammetry (CV), galvanostatic charge-discharge curves (GCD), and impedance spectroscopy (EIS). It was found that the Pt loading increased the specific capacitance from 51 F/g to 100 F/g. The ESR drop of the packaged cell decreased with the Pt loading due to the fast flow of charge through the conductive pathways. The results showed that the surface chemistry is more dominant than the surface area for determining the capacitive performance of Pt loaded AC-based packaged supercapacitors.

Bio-Derived Porous Carbon from Agar as an Anode Material for Lithium-Ion Batteries

In past decades, environmental concerns and fossil fuel depletion have spurred the development of green and renewable technologies that can efficiently convert and store energy sources. In particular, lithium-ion batteries (LIBs) have been gaining increasing attention due to their high reversible capacity, outstanding rate performance and cycling stability as well as portability and low pollution. However, the commercially available LIBs with graphite anode cannot meet the ever-increasing demand for high energy density devices, therefore, the exploring of an alternative anode is essential to enhance the energy storage capacity of LIBs. Recently, biomass-derived carbon materials have shown excellent electrochemical performance as a negative electrode, making them an ideal candidate as a new host material for lithium ions.Here we propose a one-pot, low-cost, and environmentally friendly synthesis method of a bio-derived porous carbon with a high surface area as an anode electrode for LIBs. Four chemical activators such as H2SO4, H3PO4, KOH, and ZnCl2 have been investigated as a facilitator to the formation of the porous structure of activated carbon (AC) from the agar precursor. Among the used chemical activators, AC prepared with the addition of KOH demonstrated the best electrochemical performance in a reaction with lithium metal. The initial discharge capacity reached 931 mAh g-1 and a reversible capacity of 320 mAh g-1 was maintained over 100 cycles at 0.1C. The high rate performance up to 10 C demonstrated stable cycling performance of AC from agar. Keywords: activated carbon; agar; anode; lithium-ion battery, chemical activators.Acknowledgments:This work was supported by the project 091019CRP2114 “Three-Dimensional All Solid State Rechargeable Batteries” from Nazarbayev University. Graphical abstract Disordered carbonaceous materials synthesized from an environmentally sustainable agar precursor and their electrochemical characteristics as the anode for LIBs. Figure 1

Flax-Derived Carbon: A Highly Durable Electrode Material for Electrochemical Double-Layer Supercapacitors.

Owing to their low cost, good performance, and high lifetime stability, activated carbons (ACs) with a large surface area rank among the most popular materials deployed in commercially available electrochemical double-layer (EDLC) capacitors. Here, we report a simple two-step synthetic procedure for the preparation of activated carbon from natural flax. Such ACs possess a very high specific surface area (1649 m2 g–1) accompanied by a microporous structure with the size of pores below 2 nm. These features are behind the extraordinary electrochemical performance of flax-derived ACs in terms of their high values of specific capacitance (500 F g–1 at a current density of 0.25 A g–1 in the three-electrode setup and 189 F g–1 at a current density of 0.5 A g–1 in two-electrode setup.), high-rate stability, and outstanding lifetime capability (85% retention after 150,000 charging/discharging cycles recorded at the high current density of 5 A g–1). These findings demonstrate that flax-based ACs have more than competitive potential compared to standard and commercially available activated carbons.

A comprehensive review on the synthesis, performance, modifications, and regeneration of activated carbon for the adsorptive removal of various water pollutants

Rapid urbanization has led to the generation of a large quantum of complex wastewater comprising of recalcitrant organic and inorganic pollutants. The inability of the conventional treatment techniques to bring down the recalcitrant pollutant concentrations below desired standards has paved the way for the emergence of tertiary treatment technologies. Among various tertiary treatment techniques, adsorption is widely preferred due to the ease of operation, high removal performances, and diverse on-field applications. Activated carbon (AC) has found immense popularity due to easy synthesis routes, high stability, large specific surface area (SSA), etc. The synthesis and performance of AC derived from different carbonaceous precursors for pollutants removal, the role of activation techniques, pollutant specific modifications, regeneration techniques, and their disposal, are covered in this article. Trend analysis showed that research on AC derived from agricultural waste and sludge has a high potential for at least another 50 and 25 years, respectively. Most of the precursors are chemically activated to prepare the AC, which may be further modified using the metal impregnation technique for removing specific pollutants. Among various ACs, maximum mean pore volume has been shown by sludge-based AC (1.17 cm3/g) and the maximum mean SSA value has been exhibited by husk-based AC (1339 m2/g). AC is mostly used to treat dyes and metals, followed by pharmaceuticals, pesticides, and other recalcitrant organics. Moreover, by implementing microwave-assisted and biological-based regeneration techniques, the life of the AC can be increased and may serve as an efficient adsorbent for wastewater treatment for a prolonged duration.