High Methylene Blue Adsorption Capacity Research Articles

NaOH activated Galla chinensis residue hydrochar for the adsorption of methylene blue

To achieve the resource utilization of waste materials, this study utilized Galla chinensis residue (GCR) as a raw material to synthesize green hydrochar (HC) in one step, activated with NaOH to obtain alkali-activated hydrochar (AHC), which was then used for the adsorption of organic dye methylene blue (MB). The results showed that when the temperature was 25 °C, the pH was 7 and the MB concentration was 300 mg/L, the adsorption capacity (AC) of MB by AHC was 278.97 mg/g and the removal rate was 78.67 %. Langmuir (R2 = 0.9949) and the pseudo-second-order dynamics model (R2 = 0.9983) described the adsorption behavior of MB on AHC, which was an exothermic process according to thermodynamics. The adsorption mechanism included electrostatic attraction, hydrogen bond, π-π interaction, and the pore filling effect. Even after 5 cycles of adsorption–desorption, the AHC adsorbent maintained a high AC for MB, indicating that the HC prepared from GCR was a sustainable and promising adsorbent for MB, providing a new application direction for the reuse of GCR.

Facile Fabrication of Hydroxyapatite and Bentonite Encapsulated Biopolymeric Hybrid Composites for Selective Removal of Methylene Blue

AbstractDyeing industries release their hazardous dyeing effluents into the environment which affects the human health and ecosystem. Hence, the removal of dye from waste‐water is mandatory one. In this present study, focus on the fabrication of bio‐clay‐ceramic hybrid composites by dispersing bentonite (BT) clay and ceramic hydroxyapatite (HA) into alginate (Alg) and gelatin (Gel) polymeric matrixes by in‐situ method which gives BTHAAlg and BTHAGel hybrid composites for methylene blue (MB) removal. The various adsorption influencing parameters such as shaking time, adsorbent dosage, pH and initial MB concentration were optimized under batch method. The highest MB adsorption capacities of BTHAAlg and BTHAGel composites were found to be 43.70 and 47.50 mg/g respectively with optimized conditions of 100 mg/L of initial MB concentration, 40 min shaking time and 0.1 g dosages. In pH studies, the high MB adsorption capacity of bio‐clay‐ceramic composites were noticed at pH 11. The characterization techniques like FTIR, SEM and EDAX analysis were performed to find the physico‐chemical properties of bio‐clay‐ceramic composites. The equilibrium data of hybrid composites towards MB adsorption was well fitted with Langmuir isotherm model than D‐R and Fruendlich models because of higher r and low sd values. The negative values of ▵Go at three different temperatures (303, 313 and 323 K) indicate that the spontaneous nature of MB adsorption, while positive values of ΔHo and ΔSo revealed that the MB adsorption onto hybrid composites was endothermic in nature and more randomness occurred at solid/liquid interfaces. In kinetic studies, the MB adsorption onto hybrid composites was well fitted with pseudo‐second‐order and intra‐particle diffusion models. The electrostatic attraction and hydrogen bonding plays a dominant role in MB adsorption onto BTHAAlg and BTHAGel bio‐clay‐ceramic composites. The regeneration studies proposed that the hybrid composites can be reusable upto five cycles. Hence, the developed bio‐clay‐ceramic hybrid composites were act as best adsorbents for MB removal.

Furfuryl-pyridinium-functionalization of flaxseed gum for effective methylene blue removal from aqueous solution

This study describes the modification of flaxseed gum (FSG) via furfural to obtain a furfuryl-pyridinium modified adsorbent (Flax-Py) with improved adsorption characteristics towards methylene blue (MB) versus results obtained for unmodified FSG. Materials characterization was achieved via complementary spectral methods (NMR, XPS, FT-IR, Raman, and XRD) as well as thermogravimetric analysis (TGA) and ζ-potential measurements. Synthetic modification of FSG to yield Flax-Py that led to enriched N-content (2.75 atom-% versus 0.76 atom-% for FSG), and the conversion of furfuryl to pyridinium was incomplete (ca. 50 %), where both moieties were identified. The adsorption isotherms at pH 7 showed that FSG possessed favorably high MB adsorption capacity (ca. 540 mg/g); while Flax-Py was notably lower (167 mg/g). Flax-Py facilitated 100% MB removal at low dye concentrations (1-10 mg/L) versus 50 % MB removal for the FSG bioadsorbent. Further, Flax-Py showed moderate loss of adsorption with MB (ca. 12-16% dye removal) after five regeneration cycles. Flax-Py revealed improved settling characteristics (time, density, gelation, and solubility) that facilitate enhanced phase separation of FSG fractions by circumventing the need for centrifugation. The adsorption mechanism was attributed primarily to H-bonding effects with secondary contributions due to electrostatic interactions (negative ζ-potential above pH 4.2). This study successfully modified FSG to obtain an improved adsorbent (Flax-Py) attaining nearly quantitative MB dye removal at environmentally relevant concentrations (< 15 mg/L).

Preparation of porosity-adjustable porous adsorbent materials derived from coal solid waste

Coal solid waste (CSW) was explored as precursor to prepare porous adsorption material (ACSW) by carbon dioxide activation. The effects of activation method (direct activation and pre-carbonization followed by activation), activation temperature, and activation time were systematically investigated. The burn-off characteristics of the CSW were measured, the ACSW were characterized by field emission scanning electron microscope, gas adsorption instrument and Raman spectrometer, and, in parallel, the adsorption ability was studied using methylene blue (MB) as a typical pollutant. The results showed that compared with direct activation, pre-carbonization reduced the carbon loss, increased the pore volume with pore size less than 1 nm, improved the carbon structural order and increased the MB adsorption performance. In addition, the evolution of the structure of the ACSW strongly depended on the activation temperature and time. With the increase of the activation time, the pore structure evolution underwent three stages: pore forming, expanding, and collapsing. Pore forming mainly involved clearing scattered graphite structures and amorphous carbon. Pore expanding mainly relies on consumption of regular graphite carbon crystal structure. At low temperature of 800 °C, micropores fully developed. As the activation temperature increased to 850–900 °C, pore expansion became apparent, mainly forming pores of 1–5 nm. Moreover, the MB adsorption capacity was positively correlated with the pore volume with pore size less than 5 nm. The burn-off can serve as an indicator for evaluating pore structure and the adsorption performance and when it was ∼25.5 %, the ACSW had the largest pore volume with pore size less than 5 nm and the highest MB adsorption capacity.

Adsorptive removal of methylene blue dye using durian peel waste reinforced polyvinyl alcohol‐based composite membrane

AbstractA large amount of dye effluents with biodegradable and highly toxic nature from the dyeing and finishing processes has discharged into natural water bodies without adequate treatment, which adversely impacted on aquatic life and human health. Herein, polyvinyl alcohol/agarose/maltodextrin composite membrane (PAM)‐reinforced durian skin fiber is fabricated for methylene blue (MB) uptake from aqueous medium. Structural analyses of the as‐prepared composite membrane are conducted using scanning electron microscopy, Fourier‐transform infrared spectroscopy, water contact angle, and nitrogen adsorption/desorption isotherm measurement. The important influence of experimental conditions including exposure time between adsorbates and adsorbents, initial MB concentration, solution temperature, and pH are also explored. Furthermore, thermodynamic behavior, nonlinear isotherms, and kinetics along with possible adsorption mechanism are provided to attain the insight into the adsorption nature. The results show that PAM‐reinforced durian peel waste possesses high MB adsorption capacity (105.54 mg g−1), which was controlled by diffusion and chemisorption mechanism. The thermodynamics of methyl blue removal on the composite membrane suggest that the adsorption is spontaneous, favorable, and endothermic in nature. This contribution is expected to inspire the efficient utilization of agriculture by‐products into eco‐friendly and biodegradable adsorbents to purify the dye‐contaminated water.

Design of a novel multifunctional soil conditioner based on Fe-modified hydroxyapatite/polydopamine/amino carbon nanotubes

A composite soil conditioner based on Fe-doped hydroxyapatite/polydopamine/amino carbon nanotubes (Fe-HAP@PDA@CNT-NH2) was prepared for controlling release of flavic acid (FA) fertilizers and for the treatment of soil contaminants methylene blue (MB). Firstly, Fe-doped hydroxyapatite (Fe-HAP) was prepared by hydrothermal method. Then, Fe-doped hydroxyapatite/polydopamine/aminocarbon nanotube (Fe-HAP@PDA@CNT-NH2) composite was prepared by in situ polymerization of dopamine (DA) with amino carbon nanotubes (CNT-NH2) on the Fe-HAP surface. Finally, Fe-HAP@PDA@CNT-NH2@FA composite soil conditioner was obtained by loading with FA. Scanning electron microscopy (SEM), X-Ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) were applied to analyze the composition and morphology of the composites. The loading and slow release experiments showed that Fe-HAP@PDA@CNT-NH2 owned good loading efficiency on FA and had a wide applicability with different fertilizer slow release effects in different pH environments. Adsorption experiment revealed that Fe-HAP@PDA@CNT-NH2 possessed high adsorption capacity for MB under different pH conditions. The pseudo-second order and Langmuir models discussed above can be utilized to describe the adsorption mechanism utilizing kinetic and isothermal adsorption models. In addition, the plant experiment also proved the effect of the composite soil conditioner on soil and plants. Hence, the new composite soil conditioner has a great promoting effect on soil improvement and crop growth.

Enhanced Adsorption Capacity of Methylene Blue Dye onto Kaolin through Acid Treatment: Batch Adsorption and Machine Learning Studies

Algerian kaolinite, sourced from Djebel Debbagh nuance 3 (DD3), was used as a low-cost adsorbent to remove methylene blue (MB) dye from water. Its adsorption capacity was enhanced through sulfuric acid treatment (treated-DD3). In response to the urgent demand for clean water, various technologies have been developed to address dye removal from wastewater. This study, specifically delving into the treatment of textile wastewater, examined the efficacy of treated-DD3 through adsorption processes. The acid treatment increased the surface area and pore volume of DD3. X-ray diffraction showed crystalline phases in both, with treated-DD3 having higher crystallinity. Fourier-transform infrared spectroscopy found no significant differences post-acid treatment. Scanning electron microscopy revealed DD3 had large, stacked particles with low surface area, while treated-DD3 had increased porosity and a smoother surface. Various parameters affecting MB adsorption were studied. The Langmuir and Freundlich models were used for isotherm parameters. Treated-DD3 exhibited a higher MB adsorption capacity (64.58 mg/g according to the Langmuir model) than DD3 (44.48 mg/g). Thermodynamic analysis indicated spontaneous and endothermic MB adsorption onto both DD3-BM and treated-DD3-BM systems under different pH conditions. Treated-DD3 effectively reduced chemical oxygen demand (from 304.056 mg/L to 34.44 mg/L) and biological oxygen demand (from 80 mg/L to 20 mg/L) in real textile wastewater. The adsorbent exhibited rapid removal and decolorization, surpassing 93% within the first 7 min of the experiment. The Gaussian process regression and particle swarm optimization (GPR–PSO) predicted MB adsorption capacity effectively (R = 0.9989, R2 = 0.9978, adj-R2 = 0.9978, RMSE = 1.1390, and MAE = 0.3926).

Selective separation of methylene blue from aqueous solution using Mn/Pd decorated chemically modified MoS2 nanocomposites

The presence of dyes in wastewater is posing as serious threat to human health. There are a huge number of physical, chemical, biological and hybrid methods available for the removal of colorants (dyes) from aqueous environment. In this work, we demonstrate the fabrication of new nanocomposites, MoS2-COOH/gly@M (M= Mn, Pd), with high adsorption property fabricated by chemically immobilizing manganese and palladium metallic centers onto the glycine- modified molybdenum disulfide (MoS2) material. The chemical and physical properties of adsorbents were analyzed using Fourier transform infrared spectrometer (FT-IR), thermal gravimetric analysis (TGA), X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) companied by energy dispersive X-ray and mapping (EDAX & MAP) analyses. Zeta potential (ξ) technique was also used to measure the surface charge of adsorbents. Performances of nanocomposites were investigated on the sewage as adsorbent for dye removal. Synthesized nanocomposites revealed selective adsorption of methylene blue (MB) dye from aqueous mixture of MB and methyl orange (MO). Results displayed the equivalent high adsorption capacity for MB and MO up to 553 and 619 mg/g, respectively (green reaction condition= 120 min contact time, ,25 °C, pH 2.0 and pH 7.0, in the presence of 2 mg adsorbent and 50 mg/L (30 mL) initial concentration of MO and MB). The remarkable adsorption capacity of dye by MoS2-COOH/gly@M (M= Mn, Pd) nanocomposites can be attributed to the intermolecular interactions due to the presence of the amine, hydroxyl, and carboxyl functionalities. To describe the adsorption mechanism of MO and MB dye by synthesized nanomaterials, the pseudo-first-order and pseudo-second-order kinetics were further studied. Isotherm models displayed that the adsorption of MB and MO onto the MoS2-COOH/gly@M (M= Mn, Pd) nanocomposites is more correspondent with the Freundlich model with high-correlation coefficients. The results showed that the electrostatic attraction and H-bonding interaction were the basic cause of the adsorption of these anionic and cationic dyes on the surface of the nanocomposites. One of the distinguished properties of adsorbents is their capability to selectively adsorb MB from an admixture of MO and MB. The adsorption selectively has expanded in the following order: MoS2 < MoS2-COOH/gly@Mn < MoS2-COOH/gly@Pd. Based on the results, this new type of nanocomposites has potential to act as an effective and affordable adsorbent material for dye removal from an industrial sewage.

Structural properties and photocatalytic activity of amorphous-crystalline TiO2 thin films

TiO2-coated glass plates were prepared by dip coating using TiO2 coating sol with a mixed amorphous and crystalline structure. These samples were dried at 100°C or calcined at 500°C, which were referred to as MT and CT, respectively. The TiO2 thin films on glass plates were characterized by X-ray diffraction, thermogravimetry-differential thermal analysis, X-ray photoelectron spectroscopy, Fourier transformed infrared spectroscopy, Brunauer-Emmett-Teller surface area measurement, scanning electron microscopy, and ultraviolet–visible diffuse reflectance spectra. The TiO2 thin films of MT samples had mixed amorphous and crystalline structures, while those of CT samples had only crystalline structures. The photocatalytic activity of the samples was investigated on the basis of methylene blue (MB) decomposition under ultraviolet and visible light irradiation. In the dark stabilization, MT samples had a higher MB adsorption capacity than CT samples. MT samples had a smaller amount of anatase TiO2 than CT samples, but both glass plate samples showed the same MB photocatalytic activity under ultraviolet light irradiation. We presumed that these results were because the amorphous-crystalline TiO2 thin films had a high specific surface area, so they had more adsorption and active sites. Under visible light irradiation, only the MT samples had photocatalytic activity, which can be attributed to their high visible light absorbance, which may be due to their peroxo groups, disordered structure, and larger specific surface area.

Hydrogel beads based on sodium alginate and quince seed nanoparticles for the adsorption of methylene blue

In this paper, bioadsorbents containing sodium alginate and quince seed nanoparticles were prepared using the ionotropic gelation method for the adsorption of methylene blue. The structural characterization of the bioadsorbents and nanoparticles was performed by using Fourier Transform-Infrared Spectroscopy (FT-IR), Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD), thermogravimetric (TG), and Brunauer-Emmett-Teller (BET) analysis. Cationic dye (methylene blue, MB) was used for the adsorption studies and some operational parameters such as initial pH solution, temperature, contact time, initial dye concentration, and adsorbent dose were optimized. The pseudo-first, and second order kinetics, Langmuir, and Freundlich isotherm models were used to analysis of the experiment results. The findings showed that the experimental results were fitted to the pseudo-second order kinetic and Langmuir isotherm models. The highest methylene blue adsorption capacity was obtained as 192.3 mg/g at 60 °C in the presence of sodium alginate bioadsorbent containing 5.0% quince seed nanoparticles at pH 7. The thermodynamic parameters (ΔG°, ΔH°, and ΔS°) were also calculated, and the MB adsorption on the bioadsorbents was performed as spontaneous and exothermic due to the negative value of the ΔG° and ΔH°.

Activation temperature dependence of Adonidia merrillii palm seed porous activated carbons textural properties. Adsorption of methylene blue in batch systems

From a char of Palm seed (CSP), activated carbon at 973, 1073, and 1173 K was obtained (CASPs). These temperatures developed textural properties to favor the adsorptive properties. The CASPs percentage of burning decreased with the increase of the activation temperature from 76 to 26%. These products were obtained with a CO2 flow (as activating gas) and a short time of activation. The CASPs were characterized by mercury porosimetry, adsorption of N2, CO2, and methylene blue at 77, 273, and 298 K, respectively. Wide supermicropores were obtained for CASP1173 and narrow mesoporosity was achieved for CASP973 and CASP11073 (1.4–2.0 nm and 2.0–5.0 nm, respectively). Mercury porosimetry determined that the activated carbons have mesopores with diameters smaller than 50 nm and macropores with diameters greater than 50 nm. The use of Dubinin and Langmuir models showed that the adsorption occurred in the larger diameter micropores and smaller diameter mesopores of the highest and shortest diameters (above 3.85 mmol/g). The activated carbon at 973 K showed a higher methylene blue adsorption capacity (181.03 mg/g). The MB adsorption was determined by the diameters of the adsorbent pores. For this reason, a batch adsorption system to remove this contaminant was proposed.

Waste treat waste: Alginate calcium versus alginate acid gels in upcycling waste cotton linter as composite biosorbent

Transforming waste materials into biosorbent offers a valuable solution for cost-effective water decontamination while simultaneously promoting waste upcycling. This study focused on the gelation of alginate calcium (AC) and alginate acid (AA) in recycling waste cotton linters (WCL) to create composite hydrogels for dye removal. Both hydrogel systems effectively incorporate WCL, displaying an impressive 80 wt% WCL entrapping capacity in the composite hydrogels. The presence of WCL leads to a fascinating volume expansion phenomenon, particularly noticeable in AC composite systems after freeze-drying. Additionally, the composite hydrogels demonstrate efficient adsorption of methylene blue (MB), ranging from 5 to 22 mg/g in MB dye solution (30 mg L−1), and exhibit good compatibility with various adsorption kinetic models. However, AC composite systems outperform AA composite systems and display higher MB adsorption capacity, faster adsorption rate, and more consistent performance. Mechanistic studies reveal that electrostatic forces contribute to volume expansion and dye adsorption, while the denser crosslinking structure and more abundant carboxylate groups in the AC composite system contribute to its superior performance. Our current study not only establishes the criteria for selecting proper alginate system as bio-composite hydrogel matrices, but also provides a sustainable “waste treat waste” upcycling strategy.

Efficient removal of methylene blue from aqueous solution by ZIF-8-decorated helicoidal electrospun polymer strips

Immobilization of metal-organic frameworks (MOFs) on electrospun products for wastewater treatment has garnered considerable attention in recent years. However, the effect of the overall geometry and surface-area-to-volume ratio of MOF-decorated electrospun architectures on their performances have rarely been investigated. Herein, we prepared polycaprolactone (PCL)/polyvinylpyrrolidone (PVP) strips with helicoidal geometries via immersion electrospinning. By regulating the weight ratio of PCL to PVP, the morphologies and surface-area-to-volume ratios of the PCL/PVP strips could be controlled precisely. Then, the zeolitic imidazolate framework-8 (ZIF-8) for removing methylene blue (MB) from an aqueous solution was immobilized on the electrospun strips, resulting in ZIF-8-decorated PCL/PVP strips. The key characteristics of these composite products, such as adsorption and photocatalytic degradation behavior toward MB in the aqueous solution, were carefully investigated. Owing to the desired overall geometry and high surface-area-to-volume ratio of the ZIF-8-decorated helicoidal strips, a high MB adsorption capacity of 151.6 mg g−1 was obtained, which is significantly higher than those with conventional electrospun straight fibers. In addition, higher MB uptake rates, higher recycling and kinetic adsorption efficiencies, higher MB photocatalytic degradation efficiencies, and faster MB photocatalytic degradation rates were confirmed. This work provides new insights to improve the performance of existing and potential electrospun product-based water treatment strategies.

From Waste to Added-Value Product: Synthesis of Highly Crystalline LTA Zeolite from Ore Mining Tailings.

The use of wastes is necessary to contribute to environmental sustainability. In this study, ore mining tailings were used as the raw material and precursor for the synthesis of LTA zeolite, a value-added product. Pre-treated mining tailings were submitted to the synthesis stages under specific established operational conditions. The physicochemical characterization of the synthesized products was performed with XRF, XRD, FTIR and SEM, to identify the most cost-effective synthesis condition. The LTA zeolite quantification and its crystallinity were determined as effects of the SiO2/Al2O3, Na2O/SiO2 and H2O/Na2O molar ratios used, as well as the influence of the synthesis conditions: mining tailing calcination temperature, homogenization, aging and hydrothermal treatment times. The zeolites obtained from the mining tailings were characterized by the LTA zeolite phase accompanied by sodalite. The calcination of mining tailings favored the production of LTA zeolite, and the influence of the molar ratios, aging and hydrothermal treatment times were determined. Highly crystalline LTA zeolite was obtained in the synthesized product at optimized conditions. Higher methylene blue adsorption capacity was associated with the highest crystallinity of synthesized LTA zeolite. The synthesized products were characterized by a well-defined cubic morphology of LTA zeolite and lepispheres of sodalite. The incorporation of lithium hydroxide nanoparticles over LTA zeolite synthesized (ZA-Li+) from mining tailings yielded a material with improved features. The adsorption capacity towards cationic dye was higher than for anionic dye, especially for methylene blue. The potential of using ZA-Li+ in environmental applications related to methylene blue deserves detailed study.

Facile, green approach for aqueous methylene blue dye adsorption: Coconut vinegar treated Trema orientalis wood biochar

Biochar is widely utilized in low-cost water treatment. However, chemicals used in most of the recorded activation techniques are corrosive, may cause secondary pollution, and not accessible by rural communities, reducing their value of being cost-effective. In this study, &lt;i&gt;Trema orientalis&lt;/i&gt; wood biochar (WB) was successfully activated with natural coconut vinegar employing a facile technique to produce a green adsorbent for efficient aqueous methylene blue (MB) removal. Batch studies showed a three-fold higher MB adsorption capacity of coconut vinegar treated wood biochar (CVWB) compared to WB. Percentage removal ranged between 98-79% at lower dye concentrations (50-100 mg/L) and 79-48% at higher dye concentrations (100-300 mg/L). Isotherm data best fitted to the Freundlich model. Kinetic data fitted to both pseudo second order and intraparticle diffusion models, suggesting that the adsorption was governed by a pore filling mechanism with predominant electrostatic attractions, and the reaction rate was diffusion controlled. FTIR, XPS, and water contact angle measurements confirmed increased surface oxygenated groups of CVWB. XPS showed a three-fold increase in O/C atomic ratio. BET and AFM studies gave evidence to the increased porosity. Therefore, the enhanced MB adsorption capacity of CVWB was attributed to both the increased surface oxygenated functional groups and porosity.

Porous material based on modified carbon and the effect of pore size distribution on the adsorption of methylene blue dye from an aqueous solution.

Carbon porous materials obtained through KOH activation of a furfural + hydroquinone + urotropine mixture were applied as adsorbent for the remediation of methylene blue (MB). The impact of porous structure with special attention to pore size distribution along with well-known pore volume and specific surface area on the remediation of MB was well investigated and elucidated. Findings obtained revealed that pore size distribution plays a crucial role in the liquid-phase adsorption of organic dyes like MB. By varying the synthesis mode parameters, in particular, the activating agent/precursor mass ratio, with the composition and initial components ratios remaining unchanged, samples with different pore size distribution were obtained. It was found that the material predominantly containing pores with an average equivalent diameter of ~ 3.5nm appears to be the efficient MB adsorbent. The resulting highly porous carbon materials demonstrated high MB adsorption capacity (up to 2555mg/g). Furthermore, to fully elucidate the adsorption mechanisms occurring on the obtained materials, a comprehensive mathematical processing of experimental data was performed out using the known kinetic and diffusion models (pseudo-first- and pseudo-second order, and intraparticle diffusion), as well as adsorption equilibrium isotherm models (Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich).It can be concluded that the porous carbon materials obtained and described in the present work are effective adsorbents for the removal of MB and may possess great potential for the treatment of dye-containing wastewater.

Ammonia modification of activated carbon derived from biomass via gamma irradiation vs. hydrothermal method for methylene blue removal

Local biomass (water hyacinth, “WH” and eucalyptus charcoal, “EU”) were turned to high-quality activated carbon (WHAC and EUAC) for methylene blue adsorbents. The carbonization (at 800°C for 5 hours under an N2 atmosphere) and chemical activation (KOH) were applied for the AC production. Two methods of ammonia modification were used: gamma irradiation and hydrothermal treatment, to improve the adsorption ability of AC. The nitrogen contents of WHAC and EUAC modified by hydrothermal method (3-4%) are slightly higher than that of gamma irradiation (1.5-2.0%). The sequence of methylene blue (MB) adsorption ability of WHAC is the gamma irradiation (587.92 mg/g) > the hydrothermal technique (565.15 mg/g) > unmodified (462.98 mg/g), which is similar to EUAC (552.16 > 541.88 > 453.52 mg/g, respectively). The higher MB adsorption capacity of WHAC may be due to the combination of high surface area and naturally occurring calcium oxide. Gamma irradiation successfully doped nitrogen to the WHAC surface and gives a significantly larger surface area, increasing from 1038.70 m2/g (WHAC unirradiated) to 1765.52 m2/g (WHAC irradiated at 100 kGy) without harmful chemicals, heat, and chemical waste.

Facile synthesis of carbon nanotubes and cellulose nanofiber incorporated graphene aerogels for selective organic dye adsorption

We introduced a facile and economical method to fabricate graphene aerogels (GAs) with controllable structural properties by incorporating carbon nanotubes (CNTs) and carbon nanofibers (CNFs), and its application in organic dye adsorption is demonstrated. The GAs combined with CNTs and CNFs were synthesized by the hydrothermal method. The adsorption capacity of these CNT-CNF-GA (CCGA) towards cationic dyes (rhodamine 6G (R6G) and methylene blue (MB)) and anionic dyes (methyl orange (MO)) was examined. The presence of oxygen functionalities gives an overall negative charge to CCGA, which exhibited a high adsorption capacity for cationic MB and R6G (96.1 mg/g and 79.2 mg/g, respectively) dyes and a relatively low adsorption capacity towards MO (51.6 mg/g). Further, by adjusting the hydrothermal treatment time, the oxygen functional group content and the surface area of CCGA were optimized to improve the adsorption capacity. All these imply that the porosity of GA, chemical and physical interaction of functional groups, overall charge on GA and the dye molecules, and the size of the dye molecules are the main criteria that affect the selective dye adsorption. These CCGAs exhibited a better adsorption capacity as well as good reusability, indicating their potential for practical use as a dye adsorbent.

Preparation of novel biochar containing graphene from waste bamboo with high methylene blue adsorption capacity

Biochar containing graphene (BCG) was synthesized using the precursor of bamboo biomass and K2CO3 as the activating agent utilizing microwave heating with short duration. The biochar had a typical graphene structure with abundant micropore and extremely high surface area up to 1565 m2/g. The activating agent K2CO3 played an important role in the catalytic graphitization, facilitating transformation of amorphous carbon into graphene like carbon. The adsorption experiment exhibited an excellent adsorption capacity of BCG for methylene blue (MB), with a maximum adsorption capacity of 1100 mg/g. The adsorption process was governed both by physical and chemical adsorption. The work further presents the mechanism of activation, adsorption isotherms, adsorption kinetics, adsorption thermodynamics. The experimental resulted proved the successful and fast preparation methodology for graphene contained carbon materials by microwave heating.

Synergistic effect of bulking agents and biodegradation on the pyrolysis of biodried products derived from municipal organic wastes: Product distribution and biochar physicochemical characteristics

Derived from municipal organic wastes (MOWs), biodried products (BPs) are widely accepted as carbon-neutral and renewable energy resources. In this study, the pyrolytic products of BPs, i.e., syngas, tar and biochar, were comprehensively investigated, with a special focus on the synergistic effect of bulking agents (BAs) and the modification of biodegradation. Compared with the theoretical yields (31.12%–34.94%), the interactions of MOWs and BAs promoted biochar formation (34.65%–37.74%) during pyrolysis of raw materials (RMs). Biodegradation further enhanced the biochar yield (40.73%–49.50%) but limited the liquid yields (29.49%–38.04% vs. 39.75%–43.40%) during pyrolysis of BPs. Furthermore, biodegradation also enriched H2 in the syngas and promoted the formation of phenolic compounds (30.19%–47.83% vs. 11.08%–26.55%) in the tars during BP pyrolysis. In addition, the BP-biochar presented a higher porosity of mesopores, larger total volume (0.130–0.170 cm3/g) and pore size (4.15–4.77 nm); therefore, it had a higher methylene blue adsorption capacity than the RM-biochar (50.9–84.4 vs. 21.1–44.5 mg/g). These findings suggested that the interactive effect of BAs and the modification of biodegradation were effective in upgrading the pyrolytic products, including H2-rich syngas, phenolic-rich tar and mesoporous biochar. This study provides a promising strategy for the efficient utilization of MOWs by integrating biodrying and pyrolysis.