Key factors and primary modification methods of activated carbon and their application in adsorption of carbon-based gases: A review

A novel naturally superoleophilic coconut oil-based foam with inherent hydrophobic properties for oil and grease sorption

Absorption methods using polyurethane foams (PUFs) have recently gained popularity in treating oil spills. However, conventional petroleum-based PUFs lack selectivity and are commonly surface-modified using complicated processes that require toxic and harmful solvents to enhance their hydrophobicity and oil sorption capacities. In this paper, a novel naturally superoleophilic foam with inherent hydrophobic properties has been developed through the conventional one-shot foaming method with the integration of coconut oil-based polyol. This bio-based polyol was explicitly handpicked as it is chiefly saturated, highly abundant, and inexpensive. The foam is characterized by an oil sorption capacity range of 14.89-24.65 g g-1 for different types of oil, equivalent to 578-871 times its weight. Its hydrophobic behavior is expressed through a water contact angle of ~ 139°. The foam also showcased excellent chemical stability and high recyclability without a significant loss in absorption capacity after 20 cycles. The incorporation of the coconut oil-based polyol is also shown to improve the morphological, mechanical, and thermal behavior of the foam. It can be inferred from these findings that this novel material holds great potential for revolutionizing sorbents, pioneering a more sustainable and eco-friendly functional material produced via a facile method.

Mandarin biochar-CO-TETA was utilized for Acid Red 73 dye adsorption from water, and its isotherm and kinetic studies were investigated

Environmental pollution is a major issue today due to the release of dyestuff waste into the environment through industrial wastewater. There is a need for affordable and effective adsorbents to remove harmful dyes from industrial waste. In this study, Mandarin biochar-CO-TETA (MBCOT) adsorbent was prepared and used to remove Acid Red 73 (AR73) dye from aqueous solutions. The efficiency of dye removal was influenced by various factors such as solution pH, contact time, initial AR73 dye concentration, and MBCOT dosage. All experiments were conducted at 25 ± 2 °C, and the optimal pH was determined to be 1.5. The optimal conditions for dye removal were found to be an AR73 dye concentration of 100 mg/L, an MBCOT dosage of 1.5 g/L, and a contact time of 150 min, resulting in a 98.08% removal rate. Various models such as pseudo-first-order (PFO), pseudo-second-order (PSO), film diffusion (FD), and intraparticle diffusion (IPD) were used to determine the adsorption kinetics of AR73 dye onto MBCOT. The results showed that the PSO model best explains the AR73 dye adsorption. Furthermore, Langmuir and Freundlich's isotherm models were studied to explain the adsorption mechanism using experimental data. The adsorption capacities at equilibrium (qe) in eliminating AR73 dye varied from 92.05 to 32.15, 128.9 to 65.39, 129.25 to 91.69, 123.73 to 111.77, and 130.54 to 125.01 mg/g. The maximum adsorption capacity (Qm) was found to be 140.85 mg/g. In conclusion, this study demonstrates that biochar produced from mandarin peels has the potential to be an effective and promising adsorbent for removing AR73 dye from water.

Physicochemical assessment of ammonium adsorption using a palm shell-based adsorbent activated with acetic acid: experimental and theoretical studies

The adsorption of ammonium from water was studied on an activated carbon obtained using raw oil palm shell and activated with acetic acid. The performance of this adsorbent was tested at different operating conditions including the solution pH, adsorbent dosage, and initial ammonium concentration. Kinetic and equilibrium studies were carried out, and their results were analyzed with different models. For the adsorption kinetics, the pseudo-first order equation was the best model to correlate this system. Calculated adsorption rate constants ranged from 0.071 to 0.074 g/mg min. The ammonium removal was 70-80% at pH 6-8, and it was significantly affected by electrostatic interaction forces. Ammonium removal (%) increased with the adsorbent dosage, and neutral pH condition favored the adsorption of this pollutant. The best ammonium adsorption conditions were identified with a response surface methodology model where the maximum removal was 91.49% with 2.27 g/L of adsorbent at pH 8.11 for an initial ammonium concentration of 36.90 mg/L. The application of a physical monolayer model developed by statistical physics theory indicated that the removal mechanism of ammonium was multi-ionic and involved physical interactions with adsorption energy of 29 kJ/mol. This activated carbon treated with acetic acid is promising to depollute aqueous solutions containing ammonium.

The relative dominance of surface oxygen content over pore properties in controlling adsorption and retrograde behavior of gaseous toluene over microporous carbon

The adsorption potential of activated carbon (AC) derived from macadamia nut shells (product code of Procarb-900: namely, AC-P) has been investigated using gaseous toluene as the target pollutant. The powder AC-P with high-microporosity (96%) and oxygen content (5.62%) exhibited very high adsorption capacity (214 mg·g-1) and partition coefficient (PC: 25 mol·kg-1·Pa-1) against 100 ppm (10 Pa) toluene at 99% breakthrough levels (1 atm dry N2). The factors governing toluene adsorption were explored with respect to the key variables such as surface functional groups, pore size distribution, sorbent bed mass (50, 100, and 150 mg), and particle size (i.e., 0.212-0.6 mm (powder AC: PAC)) vs. 0.6-2.36 mm (granular AC: GAC)). Accordingly, the adsorption process was physical, mainly due to the non-polar interactions (i.e., π-π interactions) between the adsorbent and adsorbate molecules. The high affinity of AC-P at low breakthrough levels was obtained through a combination of smaller particle size (PAC) and larger adsorbent mass (i.e., 150 mg) with the appearance of a very pronounced retrograde phenomenon (e.g., at < 1% breakthrough level). As such, toluene adsorption appeared to be affected more sensitively by particle size and adsorbent mass (especially at low breakthrough levels) than by high microporosity. Most importantly, the oxygen content of AC emerges as one of the key factors governing the maximum capacity, as the changes in pore volume are not crucial to explain the observed adsorption patterns of toluene.

Tuning the Hierarchical Pore Structure and the Metal Site in a Metal-Organic Framework Derivative to Unravel the Mechanism for the Adsorption of Different Volatile Organic Compounds

Volatile organic compounds (VOCs) are one of the main classes of air pollutants, and it is important to develop efficient adsorbents to remove them from the atmosphere. To do this most efficiently, we need to understand the mechanism of VOC adsorption. In this work, we described how the metal organic framework (MOF), ZIF-8, was used as a precursor to generate MOF derivatives (Zn-GC) through temperature-controlled calcination, which had adjustable metal sites and hierarchical pore structure. It was used as a model adsorbent to study the adsorption and desorption characteristics of different VOCs. Zn-GC-850 with developed pores exhibited higher adsorption performance for the benzene series, whereas Zn-GC-650 with more metal sites had a better adsorption capacity for oxygen-containing VOCs. By tuning the molecular structure of the VOCs, we revealed the adsorption mechanism of different VOCs at the molecular level. The more developed hierarchical pore structure obtained at the higher temperature facilitates the diffusion of the benzene series, and the noncovalent interaction between their methyl group(s) and the carbonized MOF derivatives improves the adsorption affinity; while the higher exposure of Zn sites obtained at lower temperature favors the adsorption of oxygen-containing VOCs by Zn-O bonds. The mass transfers of VOCs and the role of the adsorbent were simulated by multiple theoretical models. This study strengthens the basis for the design and optimization of the adsorbent and catalyst for VOCs treatment.

Improving the adsorption performance of non-polar benzene vapor by using lignin-based activated carbon

Both indoor and outdoor contamination continually contain benzene vapor. It has primary concerns about long-term health risks to the living environment. Benzene is a crucial airborne pollutant in the environment due to its apparent acute toxicity, high volatility, and poor degradability. It is especially urgent to restrain benzene emissions due to the persistent concentration increase and stringent processes. Benzene adsorption is a highly efficient mechanism with low cost, low energy consumption, and a simple process. In this study, biomass-derived porous carbon materials (TCACs) were synthesized by pyrolysis activation combined with H3PO4, HNO3, and HCl. TCAC44 has the best activation conclusion, showing that surface area and pore volume were 1107 m2/g and 0.58 cm3/g treated with H3PO4 and so was chosen for subsequent benzene adsorption/desorption tests. The adsorption capacities of benzene for TCAC44 were increased from 58 mg/g for 35 °C + 95% RH to 121 mg/g for 25 °C + 15% RH and presented a higher adsorption capacity of benzene than TCAC101 and TCAC133. Otherwise, well recyclability of TCAC44 was revealed as the benzene adsorption capacity reductions were 22.49% after five adsorption-desorption cycles. Furthermore, the present study established the property-application relationships to promote and encourage future research on the newly synthesized innovative TCAC44 for benzene removal.

Management of typical VOCs in air with adsorbents: status and challenges

The serious harm of volatile organic compounds (VOCs) to the ecological environment and human health has attracted widespread attention worldwide. With economic growth and accelerated industrialization, the anthropogenic emissions of VOCs have continued to increase. The most crucial aspect is to choose the appropriate adsorbent, which is very important for the VOCs removal. The search for environmentally friendly VOCs treatment technologies is urgent. The adsorption method is one of the most promising VOCs emission reduction technologies with the advantages of high cost-effectiveness, simple operation, and low energy consumption. One of the most critical aspects is the selection of the appropriate adsorbent, which is very important for the removal of VOCs. This work provides an overview of the sources and hazards of VOCs, focusing on recent research advances in VOCs adsorption materials and the key factors controlling the VOCs adsorption process. A summary of the key challenges and opportunities for each adsorbent is also provided. The adsorption capacity for VOCs is enhanced by an abundant specific surface area; the most efficient adsorption process is achieved when the pore size is slightly larger than the molecular diameter of VOCs; the increase in the number of chemical functional groups contributes to the increase in adsorption capacity. In addition, methods of activation and surface modification to improve the adsorption capacity for VOCs are discussed to guide the design of more advanced adsorbents.

Potential of fluorescent tracers to appraise biochar amendment strategies for pesticide mitigation - insights from comparative sorption

Mitigation of pesticide dispersion in soil and water is required to protect ecosystem health and the anthropic uses of water bodies. Biochar amendments have been suggested to reduce pesticide dispersion due to their high sorption potentials. Nevertheless, appraisals at different scales have been limited by the costs of pesticide analyses. The aim of this study was to evaluate the potential of two fluorescent tracers, uranine (UR) and sulforhodamine B (SRB), for use as pesticide proxies in the context of biochar amendments used for mitigation purposes. Therefore, we compared the sorption processes of both fluorescent tracers and those of three pesticides, glyphosate, 2,4-D, and difenoconazole for soils; three wood biochars (pine, oak, and beech/charm blend); and soil/biochar mixtures representing agricultural usages. The results showed that the sorption of glyphosate by soil was unaffected by amendment with the tested pine, oak, and wood blend biochars. In contrast, the sorption coefficients of UR, SRB, 2,4-D, and difenoconazole were significantly increased with these biochar amendments. SRB, in particular, exhibited sorption behavior similar to that of the hydrophobic fungicide difenoconazole. This indicates promise for the use of SRB as a proxy for hydrophobic pesticides, in testing biochar amendments.

High Efficiency of Formaldehyde Removal and Anti-bacterial Capability Realized by a Multi-Scale Micro-Nano Channel Structure in Hybrid Hydrogel Coating Cross-Linked on Microfiber-Based Polyurethane

Inspired by the transpiration in the tree stem having a vertical and porous channel structure, high efficiency of formaldehyde removal is realized by the multi-scale micro-nano channel structure in a hybrid P(AAm/DA)-Ag/MgO hydrogel coating cross-linked on microfiber-based polyurethane. The present multi-scale channel structure is formed by a joint effect of directional freezing and redox polymerization as well as nanoparticles-induced porosity. Due to the large number of vertically aligned channels of micrometer size and an embedded porous structure of nanometer size, the specific surface area is significantly increased. Therefore, formaldehyde from solution can be rapidly adsorbed by the amine group in the hydrogels and efficiently degraded by the Ag/MgO nanoparticles. By only immersing in formaldehyde solution (0.2 mg mL^-1) for 12 h, 83.8% formaldehyde is removed by the hybrid hydrogels with a multi-scale channel structure, which is 60.8% faster than that observed in hydrogels without any channel structure. After cross-linking the hybrid hydrogels with a multi-scale channel structure to microfiber-based polyurethane and exposing to the formaldehyde vapor atmosphere, 79.2% formaldehyde is removed in 12 h, which is again 11.2% higher than that observed in hydrogels without any channel structure. Unlike the traditional approaches to remove formaldehyde by the light catalyst, no external conditions are required in our present hybrid hydrogel coating, which is very suitable for indoor use. In addition, due to the formation of free radicals by the Ag/MgO nanoparticles, the cross-linked hybrid hydrogel coating on polyurethane synthetic leather also shows good anti-bacterial capability. 99.99% of Staphylococcus aureus can be killed on the surface. Based on the good ability to remove formaldehyde and to kill bacteria, the obtained microfiber-based polyurethane cross-linked with a hybrid hydrogel coating containing a multi-scale channel structure can be used in a broad field of applications, such as furniture and car interior parts, to simultaneously solve the indoor air pollution and hygiene problems.

BET and Kelvin Analyses by Thermogravimetric Desorption

Porous solids with nanometer-sized pores and large surface areas are a highly important class of materials. Uses of such materials include filtration, batteries, catalysts, and carbon sequestration. These porous solids are characterized by their surface areas, typically >100 m²/g, and pore size distributions. These parameters are typically measured using cryogenic physisorption, frequently referred to as Brunauer-Emmett-Teller (BET) analysis when BET theory is applied to interpret experimental results. Cryogenic physisorption and related analysis elucidate how a particular solid interacts with the cryogenic adsorbate, but this can be a poor predictor of how that solid will interact with other adsorbates, limiting the applicability of the results. Additionally, the cryogenic temperatures and deep vacuum required for cryogenic physisorption can cause kinetic limitations and experimental difficulties. This method nevertheless remains the standard technique to characterize porous materials for a wide variety of applications due to limited other options. In this work, a thermogravimetric desorption technique for determining surface areas and pore size distributions of porous solids available to adsorbates having boiling points above ambient temperature at ambient pressure is presented. A thermogravimetric analyzer (TGA) is used to measure temperature-dependent adsorbate mass loss, and isotherms are derived. For systems that exhibit multilayer formation, BET theory is applied to isotherms to derive specific surface areas. For systems that do not exhibit multilayer formation, the Kelvin equation is applied to determine pore size distributions and surface areas for the porous materials. In this study, the thermogravimetric method is applied to four adsorbents and two adsorbates─water and toluene─and results are compared to cryogenic physisorption results.

Synthesis of double-shelled periodic mesoporous organosilica nanospheres/MIL-88A-Fe composite and its elevated performance for Pb2+ removal in water

Herein, we report the synthesis of double-shelled periodic mesoporous organosilica nanospheres/MIL-88A-Fe (DSS/MIL-88A-Fe) composite through a hydrothermal method. To survey the structural and compositional features of the synthesized composite, a variety of spectroscopic and microscopic techniques, including FT-IR, XRD, BET, TEM, FE-SEM, EDX, and EDX-mapping, have been employed. A noteworthy point in this synthesis procedure is the integration of MOF with PMO to increase the adsorbent performance, such as higher specific surface area and more active sites. This combination leads to achieving a structure with an average size of 280 nm and 1.1 μm long attributed to DSS and MOF, respectively, microporous structure and relatively large specific surface area (312.87 m²/g). The as-prepared composite could be used as an effective adsorbent with a high adsorption capacity (250 mg/g) and quick adsorption time (30 min) for the removal of Pb²⁺ from water. Importantly, DSS/MIL-88A-Fe composite revealed acceptable recycling and stability, since the performance in Pb²⁺ removal from water remained above 70% even after 4 consecutive cycles.

Adsorption of heavy metal onto biomass-derived activated carbon: review

Due to the rapid development of the social economy and the massive increase in population, human beings continue to undertake processing, and commercial manufacturing activities of heavy metals, which has caused serious damage to the environment and human health. Heavy metals lead to serious environmental problems such as soil contamination and water pollution. Human health and the living environment are closely affected by the handling of heavy metals. Researchers must find several simple, economical and practical methods to adsorb heavy metals. Adsorption technology has been recognized as an efficient and economic strategy, exhibiting the advantages of recovering and reusing adsorbents. Biomass-derived activated carbon adsorbents offer large adjustable specific surface area, hierarchically porous structure, strong adsorption capacity, and excellent high economic applicability. This paper focuses on reviewing the preparation methods of biomass-derived activated carbon in the past five years. The application of representative biomass-derived activated carbon in the adsorption of heavy metals preferentially was described to optimize the critical parameters of the activation type of samples and process conditions. The key factors of the adsorbent, the physicochemical properties of the heavy metals, and the adsorption conditions affecting the adsorption of heavy metals are highlighted. In addition, the challenges faced by biomass-derived activated carbon are also discussed.

Adsorption Capacity and Desorption Efficiency of Activated Carbon for Odors from Medical Waste

Five types of odor-emitting exhaust gases from medical waste were selected, and their adsorption capacity and desorption efficiency were investigated using activated carbon. The selected gases included polar gases (hydrogen sulfide (H2S) and ammonia (NH3)) and non-polar gases (acetaldehyde (AA), methyl mercaptan (MM), and trimethylamine (TMA))). Commercial activated carbon with a specific surface area of 2276 m2/g was used as the adsorbent. For the removal of odor from medical waste, we investigated: (1) the effective adsorption capacity of a single gas (<1 ppm), (2) the effect of the adsorbed NH3 gas concentration and flow rate, and (3) the desorption rate using NH3 gas. The values of the effective adsorption capacity of the single gas were in the following order: H2S < NH3 < AA < MM < TMA, at 0.2, 4.2, 6.3, 6.6, and 35.7 mg/g, respectively. The results indicate that polar gases have a lower effective adsorption capacity than that of non-polar gases, and that the size of the gas molecules and effective adsorption capacity exhibit a proportional relationship. The effective adsorption performance of NH3 gas showed an increasing trend with NH3 concentration. Therefore, securing optimal conditions for adsorption/desorption is imperative for the highly efficient removal of odor from medical waste.

A Peripherally Located Air Recirculation Device Containing an Activated Carbon Filter Reduces VOC Levels in a Simulated Operating Room

Electrosurgery procedures produce airborne contaminants including volatile organic compounds (VOCs). The effectiveness of commercial grade activated carbon at removing toluene, a typical VOC, from the air in an enclosed simulated operating room (OR) when interfaced with an air recirculation device was tested. The concentration of toluene in the air was measured using gas sensitive semiconductor VOC sensors. When the air recirculation device containing activated carbon was turned on, the concentration of toluene in the air decayed exponentially. When the device was off, the toluene concentration reduced much more slowly. After 130 min, a VOC sensor placed near the air recirculation device showed VOC reductions of approximately 30% when the device is on and less than 1% when the device is off. Changing the activated carbon filter after 22 h of constant use showed an abrupt increase in the rate of toluene removal.

Carbon Dioxide Adsorption over Activated Carbons Produced from Molasses Using H2SO4, H3PO4, HCl, NaOH, and KOH as Activating Agents

Cost-effective activated carbons for CO2 adsorption were developed from molasses using H2SO4, H3PO4, HCl, NaOH, and KOH as activating agents. At the temperature of 0 °C and a pressure of 1 bar, CO2 adsorption equal to 5.18 mmol/g was achieved over activated carbon obtained by KOH activation. The excellent CO2 adsorption of M-KOH can be attributed to its high microporosity. However, activated carbon prepared using HCl showed quite high CO2 adsorption while having very low microporosity. The absence of acid species on the surface promotes CO2 adsorption over M-HCl. The pore size ranges that are important for CO2 adsorption at different temperatures were estimated. The higher the adsorption temperature, the more crucial smaller pores were. For 1 bar pressure and temperatures of 0, 10, 20, and 30 °C, the most important were pores equal and below: 0.733, 0.733, 0.679, and 0.536 nm, respectively.

Activated Carbon Modified by Ester Hydrolysis of Ethyl Acetate for Water Vapor Adsorption Enhancement

To improve water vapor adsorption, this study employed oxalic acid–ethyl acetate acidic hydrolysis to modify honeycomb activated carbon and introduce hydrophilic functional groups. Scanning electron microscopy (SEM), Boehm titration, Fourier transform infrared spectroscopy (FT-IR), and an automatic surface area analyzer (BET) were used to characterize the microscopic morphology, surface functional groups, specific surface area, and pore size changes. The results showed that, when the concentration of oxalic acid is 0.0006 mol/cm3, the specific surface area is 179.06 m2/g. After hydrolysis with ethyl acetate, the original functional groups became more abundant, while the number of total acidic functional groups on the surface grew from 0.497 mmol/g to 1.437 mmol/g. The static water vapor adsorption experiments were conducted on modified activated carbon under constant temperature and humidity conditions. Compared with unmodified activated carbon, the activated carbon modified with 0.0006 mol/cm3 oxalic acid increased the adsorption capacity of water vapor by 15.7%. The adsorption capacity of activated carbon after being combined with 0.0006 mol/cm3 oxalic acid and ester hydrolysis modification increased by 37.1%. At the same temperature, the adsorption capacity increased with a higher relative humidity. At the same relative humidity, the adsorption capacity decreased as the temperature rose. Therefore, this modification method may provide clues for the application of enhancing the hygroscopic ability of activated carbon.

Activated Carbon-Loaded Titanium Dioxide Nanoparticles and Their Photocatalytic and Antibacterial Investigations

Activated carbon doping TiO2 nanoparticles were synthesised by zapota leaf extract using the co-precipitation method. The bio-constituents of plant compounds were used in the reactions of stabilization and reductions. The carbon loading on the TiO2 nanoparticles was characterised by XRD, FTIR, UV-DRS, SEM with EDX, and TEM analysis. The loading of activated carbon onto the TiO2 nanoparticles decreased the crystallite size and optical bandgap, and their doping improved the surface structure of AC/TiO2 nanoparticles. Mesoporous/microporous instability was remodified from the activated carbon, which was visualised using SEM and TEM analysis, respectively. The photocatalytic dye degradation of Rh-B dye was degraded in TiO2 and AC/TiO2 nanoparticles under visible light irradiation. The degradation efficiencies of TiO2 and AC/TiO2 nanoparticles were 73% and 91%, respectively. The bacterial abilities of TiO2 and AC/TiO2 nanoparticles were examined by E. coli and S. aureus. The water reclamation efficiency and bactericidal effect of TiO2 and AC/TiO2 nanoparticles were examined via catalytic dye degradation and bacterial efficiency of activated carbon-doped titanium dioxide nanoparticles.

Phytoremediation of indoor formaldehyde by plants and plant material

Formaldehyde evolves from various household items and is of environmental and public health concern. Removal of this contaminant from the indoor air is of utmost importance and currently, various practices are in the field. Among these practices, indoor plants are of particular importance because they help in controlling indoor temperature, moisture, and oxygen concentration. Plants and plant materials studied for the purpose have been reviewed hereunder. The main topics of the review are, mechanism of phytoremediation, plants and their benefits, plant material in formaldehyde remediation, and airtight environmental and health issues. Future research in the field is also highlighted which will help new researches to plan for the remediation of formaldehyde in indoor air. The remediation capacity of several plants has been tabulated and compared, which gives easy access to assess various plants for remediation of the target pollutant. Challenges and issues in the phytoremediation of formaldehyde are also discussed.Novelty statement: Phytoremediation is a well-known technique to mitigate various organic and inorganic pollutants. The technique has been used by various researchers for maintaining indoor air quality but its efficiency under real-world conditions and human activities is still a question and is vastly affected relative to laboratory conditions. Several modifications in the field are in progress, here in this review article we have summarized and highlighted new directions in the field which could be a better solution to the problem in the future.

Conversion of Waste Biomass into Activated Carbon and Evaluation of Environmental Consequences Using Life Cycle Assessment

In this article, activated carbon was produced from Lantana camara and olive trees by H3PO4 chemical activation. The prepared activated carbons were analyzed by characterizations such as scanning electron microscopy, energy-dispersive X-ray spectroscopy, Brunauer–Emmett–Teller, X-ray diffraction, thermogravimetric analysis, and Fourier transform infrared spectroscopy. H3PO4 is used as an activator agent to create an abundant pore structure. According to EDX analysis, the crystalline structure destroys and increases the carbon content of the olive tree and Lantana camara by 77.51 and 76.16%, respectively. SEM images reveal a porous structure formed as a result of H3PO4 activation. The Brunauer–Emmett–Teller (BET) surface area of the olive tree and Lantana camara activated carbon was 611.21 m2/g and 167.47 m2/g, respectively. The TGA analysis of both activated carbons shows their thermal degradation starts at 230 °C but fully degrades at temperatures above 450 °C. To quantify the potential environmental implications related to the production process of the activated carbon (AC) from olive trees, the life cycle assessment (LCA) environmental methodology was employed. For most of the tested indicators, chemical activation using H3PO4 showed the greatest ecological impacts: the ozone layer depletion potential (42.27%), the acidification potential (55.31%), human toxicity (57.00%), freshwater aquatic ecotoxicity (85.01%), terrestrial ecotoxicity (86.17%), and eutrophication (92.20%). The global warming potential (5.210 kg CO2 eq), which was evenly weighted between the phases, was shown to be one of the most significant impacts. The total energy demand of the olive tree’s AC producing process was 70.521 MJ per Kg.

Comparison of Novel Biochars and Steam Activated Carbon from Mixed Conifer Mill Residues

There is increasing demand in environmental remediation and other sectors for specialized sorbents made from renewable materials rather than hard coals and minerals. The proliferation of new pyrolysis technologies to produce bio-based energy, fuels, chemicals, and bioproducts from biomass has left significant gaps in our understanding of how the various carbonaceous materials produced by these systems respond to processes intended to improve their adsorption properties and commercial value. This study used conventional steam activation in an industrial rotary calciner to produce activated carbon (AC) from softwood biochars made by three novel pyrolysis systems. Steam was injected across four heating zones ranging from 816 °C to 927 °C during paired trials conducted at calciner retention times of 45 min and 60 min. The surface area of the three biochars increased from 2.0, 177.3, and 289.1 m2 g−1 to 868.4, 1092.9, and 744.8 m2 g−1, respectively. AC iodine number ranged from 951 to 1218 mg g−1, comparing favorably to commercial AC produced from bituminous coal and coconut shell. The results of this study can be used to operationalize steam activation as a post-processing treatment for biochar and to expand markets for biochar as a precursor in the manufacture of specialized industrial sorbents.