MB Adsorption Capacity Research Articles

Preparation of ZIF‐8‐Based Functionalized Magnetic Nanocomposites and Their Application in Aqueous Environment

ABSTRACTIn this study, a functionalized magnetic powder complex porous carbon derived from ZIF‐8 (ZIF‐8@Na‐Cit@Fe3O4NPs@AC(500°C)) was prepared and applied for the waste liquid containing MB, TC, and Cu2+ adsorption removal. The ZIF‐8@Na‐Cit@Fe3O4NPs@AC(500°C) perfectly inherited the feature of parent ZIF‐8, posed a high specific surface area (SBET = 812.73 m2 g−1), be rich in surface nitrogen functional groups, and resulting in a good dynamic adsorption of the MB, TC, and Cu2+. The ZIF‐8@Na‐Cit@Fe3O4NPs@AC(500°C) exhibited the best adsorption performance of high‐concentration waste liquid containing MB, TC, and Cu2+, with equilibrium adsorption capacity of MB (408 mg g−1), TC (417 mg g−1), and Cu2+ (386 mg g−1), respectively. The acetone and toluene adsorption were spontaneously and exothermic, given the negative values of free energy (ΔG) and enthalpy (ΔH). The difference of MB, TC, and Cu2+ adsorption on ZIF‐8@Na‐Cit@Fe3O4NPs@AC(500°C) attributed to the affinity difference (polarity and molecular diameter) and the nitrogen‐containing functional groups (π‐π interaction and electrostatic attraction). Therefore, it was found that ZIF‐8@Na‐Cit@Fe3O4NPs@AC(500°C) could effectively adsorb MB, TC, and Cu2+, and ZIF‐8@Na‐Cit@Fe3O4NPs@AC(500°C) could remove more than 70% of the above pollutants after repeated use for four times; it has a good application prospect.

Green, sustainable and eco-friendly approach for extraction of silica nanoparticles from Ananas comosus and Saccharum ravannae: a comparative study of dye removal from aqueous solution

ABSTRACT Silica nanoparticles (SiNPs) were extracted in an eco-friendly manner from the crown of Ananas comosus (pineapple, AC SiNPs) and leaves of Saccharum ravannae (weed grass, SR SiNPs). Initial studies were performed to examine the adsorption of various cationic (Methylene blue, MB; Safranin, SA), anionic (Trypan Blue, TB; Eosin yellow, EY), and neutral dyes (Neutral red, NR). The investigation revealed that the maximum removal was achieved at an adsorbent dose of 1 g L−1 at an optimum pH of 7–8, at an equilibrium contact time of ∼15 mins for the dye concentration of 10 mg L−1 at 298 K. Adsorption followed the pseudo-second-order kinetic model and Freundlich isotherm model, indicating multi-layered heterogeneous adsorption. The maximum adsorption capacity (qmax) for MB, SA, and NR was found to be 81.3 mg g−1, 21.74 mg g−1, and 24.75 mg g−1 respectively, for AC SiNPs. The qmax for SR SiNPs was found to be 78.12 mg g−1, 47 mg g−1, and 70 mg g−1 for MB, SA, and NR respectively. Moreover, desorption studies showed that till 4–5 cycles, >90% of the removal efficiency was retained. Thus, the biogenic and non-toxic SiNPs can be a greener, eco-friendly alternative material for dye removal from wastewater.

Efficient construction of low shrinkage xerogels via coordination-catalyzed in-situ polymerization for activated carbon xerogels with multi-dyes adsorption

Obtaining large specific surface areas (SSA) for carbon xerogels poses a significant challenge due to the inevitable volume shrinkage of xerogel. Here, the Zn2+ coordination-catalyzed in-situ polymerization approach was proposed to fabricate xerogels with a low shrinkage of 13.03 % and a short preparation period of 24 ​h. In resorcinol-formaldehyde (RF) polymerization, ZnCl2 could accelerate the reaction kinetics through the coordination of the Zn2+ and hydroxyl groups. The gel network with adjustable RF particles (46.5 nm-1.89 ​μm) and narrow neck structures was constructed by changing ZnCl2 and ethanol contents, which could resist volume shrinkage during atmospheric drying without solvent exchange. The activated carbon xerogels (ACXs) with hierarchical structure were designed by one-step carbonization/activation due to the pore-forming of ZnCl2. The obtained ACXs showed a large SSA of 1689 ​m2/g, multi-dyes adsorption capacity (methylene blue, Congo red, methyl orange, and Sudan III were 625.90, 359.46, 320.69, and 453.92 ​mg/g, respectively), and reusability of 100 %. The maximum monolayer MB adsorption capacity was 630.28 ​mg/g. This work presents an efficient strategy to design porous nanomaterials with low shrinkage and large SSA, which illustrates promising applications in separation, adsorption, and photoelectric catalysis.

Microwave-assisted utilization of kraft lignin-derived activated carbon for efficient dye removal

The use of conventional petrochemical-based carbon precursors, high-energy pyrolysis-based carbonization processes, and difficulties in designing sustainable processes using activated carbon have hampered the sustainable production of activated carbon and its use in wastewater treatment processes. In this study, to overcome these limitations in the production and application of existing petrochemical-based activated carbon as a water treatment material, biomass-based kraft lignin was used as an eco-friendly carbon precursor. In addition, to increase process efficiency, activated carbon was prepared using energy-intensive microwave-assisted carbonization and applied to the dye wastewater removal process. First, kraft lignin was successfully converted into microporous activated carbon within 10 min through microwave-assisted carbonization and chemical activation processes. As a result, kraft lignin-derived activated carbon showed excellent adsorption capacity for MB of 543.82 mg/g and AO of 548.54 mg/g, respectively. In addition, through heat treatment using microwaves (low power conditions of 450 W, treatment within 2 min), it was possible to successfully achieve thermal decomposition of the adsorbed dye and recovery of the pores and texture properties of activated carbon. Finally, kraft lignin-derived activated carbon showed an excellent reuse efficiency of more than 97 %, even under the condition of reuse 5 times.

Preparation of highly microporous activated carbon by utilizing inherent iron in coal through CO2 and steam co-activation for improving CO2 capture and methylene blue removal

Pore-tailoring by utilizing the inherent iron mineral in coal for highly microporous activated carbon (AC) preparation for boosting adsorption ability is a promising strategy. In this work, AC-XFeS2 (X indicates the contents of pyrite in coal, 0–3 wt.%) was prepared via blending demineralized Taixi coal and pyrite and followed by CO2 and steam co-activation. The iron minerals transformation, AC physicochemical textural development and performance were investigated by various analyses. The results indicate that: (1) Pyrite (FeS2) can transform into magnetite (Fe3O4) and hematite (Fe2O3) during CO2 and steam co-activation. Pyrite declines the graphitization degree and enhances the increment of AC’s C=O, COO, and π–π* content. Pyrite favors the increase of AC’s micropore porosity. High SBET and Smic of 1587 m2/g and 949 m2/g of AC-1FeS2 were achieved, which is higher by 13.5% and 83.6% than AC of 1398 m2/g and 517 m2/g, respectively. (2) The CO2 adsorption capacity of AC-1FeS2 is up to 2.06 mmol/g at 25 °C and 1.0 bar, which is higher by 11.3% than 1.85 mmol/g of AC. The enhancement of micropore by pyrite is the main aspect of improving CO2 capture. (3) AC-1FeS2 presents maximum MB adsorption capacity, reaching 63.3 mg/g, which is higher by 19.3% than 53.3 mg/g of AC. A serious of kinetics models was studied and the MB adsorption process could be better reflected by Pseudo second-order kinetics (R2=0.9538). The enhanced pore-filling, π–π* stacking and C=O complexation are one aspect of improving MB removal. In addition, the effect of Fe-O bonds or magnetic particles including Fe3O4 also enhances MB removal. The results of this investigation could provide new avenues and theoretical support for cost-effective AC with highly microporous production by utilizing high-iron-sulfur coal, to some extent, guide the actual industrial application.

Garlic straw-derived composite hydrogel via electron beam irradiation for adsorptive removal of methylene blue

The study presents the development and optimization of a novel garlic straw-based composite hydrogel synthesized using electron beam irradiation for adsorption of common harmful organic pollutants like methylene blue dye (MB). The composite hydrogel was prepared from garlic straw (GS) mixed with (polyvinyl alcohol/Pectin) (PVA/Pt) copolymers using an eco-friendly technique of electron beam (EB) radiation for crosslinking. The synthesis process and parameters were optimized. The total PVA/Pt content 20wt% of composition 70/30 includes 20wt% GS at 35 kGy was chosen as the most suitable condition for optimization. The structure, morphology, and thermal properties were studied using different instruments. The resulting (PVA/Pt)-GS composite hydrogel exhibited excellent adsorption capacity for MB, showcased through comprehensive investigations of isotherms, kinetics, and thermodynamics. The maximum adsorption capacity of PVA/Pt-GS for MB was 505 mg/g at pH 9. Isotherm studies revealed the adsorption mechanism, while kinetic analyses provided insights into the adsorption rate. Thermodynamic investigations elucidated the spontaneity and feasibility of the adsorption process.

Synthesis of multifunctional mesoporous geopolymer under hydrothermal curing: High mechanical resistance and efficient removal of methylene blue from aqueous medium

This study created green multifunctional geopolymeric sorbent material with strong cationic dye adsorption capacity and superior mechanical strength to broaden lead sludge (LS)-based geopolymer applications. In this study, two geopolymeric sorbents (Go and G) were fabricated using slag blended with 0 and 50 wt% LS, respectively and activated with 6 wt% NaOH. The Go and G specimens were normally cured for up to 28 days, while G specimens were hydrothermally cured at different steam-pressures to modify/improve histological characteristics as well as mechanical resistance. The selected sorbents were characterized via XRD, FTIR, TGA/DTG, XPS, N2-adsorption/desorption and SEM/EDX techniques. G/5 bar′s high strength and adsorption capacity may be due to the production of CSH, CAH, CASH, and NASH, which formed a fine mesoporous zeolitic structure with the highest BET-surface area (64.55 m2/g) and lowest BJH-maximum pore diameter (9.68 nm). The maximum MB adsorption capacity of the synthesized adsorbent was 230.4 mg/g.

Performance investigation on a self-powered microbial pollutant adsorption cell with N-LAC/PVDF cation exchange membrane

A high-efficiency, self-powered microbial pollutant adsorption cell with an N-LAC/PVDF cation exchange membrane was proposed to remove metal ions and organic dyes in high-salt wastewater. Nitrogen-doped alkali lignin (N-LAC) was synthesized using chitosan nanoparticles (CS) and alkali lignin (AL) using a blending method. The N-LAC/PVDF cation exchange membrane was prepared by chemically grafting polyvinylidene fluoride (PVDF). With modification, hydroxyl, carboxyl, carbonyl, and other hydrophilicity groups were introduced into the cation exchange membrane. The addition of N-LAC improved the membrane's hydrophilicity and adsorption capacity. FITR and SEM, respectively, characterized the surface morphology of the exchange membrane. The result showed that the contact angle reached 74.89° when the amount of N-LAC was 1 wt.%, and the desalination efficiency was 93.5 %, which increased by 70 %. The adsorption capacity of organic dye Pb and metal ion MB was 91 % and 94 %, respectively, showing an increase of 31.9 % and 43.5 %.

Adsorption kinetics behavior of MB dye on CaO nanosheets

The work reported herein demonstrates the fabrication of CaO nanosheets employing a thermal decomposition method. The obtained CaO nanosheets were characterized using TEM, BET, XRD, EDX, and FTIR instruments. Moreover, the effect of initial dye concentration and pH on MB removal by CaO nanosheets was studied. The result showed that the nanoparticles have sizes around 100 nm, and the CaO nanosheets have an average diameter of 50 nm. Meanwhile, the average pore diameter and surface area of CaO are 15.847 Å and 5.881 m2. g−1 , respectively. Numerical models based on Temkin, Freundlich, and Langmuir were applied to adsorption data to better understand the MB dye adsorption onto CaO nanoparticles. The sorption findings demonstrated a stronger fit with the Temkin model (R2 = 0.983) compared to the Freundlich model (R2 = 0.947) and Langmuir model (R2 = 0.968). The maximum adsorption capacity of MB on the CaO nanoparticles is 688.01 mg/g. The investigation determined that the adsorption kinetics adhered to the Pseudo-second-order kinetic model(R2 =0.982).

Methylene blue and methyl orange removal from wastewater by magnetic adsorbent based on activated carbon synthesised from watermelon shell

The novel magnetic nanocomposites activated carbon (MWMSC) was prepared from activated carbon (AC), produced from watermelon shell through pyrolysis method. The effect of various adsorption parameters such as contact time, pH of the dye solution and MWMSC dose was studied. The optimum conditions were found to be the contact time of 60 and 40 min (MB & MO), pH of 6.0 and 3.0 for MB and MO, adsorbent dose of 100 mg (MB & MO) respectively. The adsorbents were characterized by FTIR, BET, TEM, SEM and EDX analysis techniques. Adsorption isotherms were used to test the experimental data and result is well-fitted to the Langmuir model with a maximum adsorption capacity of MB and MO was 303.30 and 345.70 mg g−1. Adsorption kinetics were well-fitted with the pseudo second-order model. The thermodynamics of the dye adsorption revealed that the adsorption is thermodynamically favourable, spontaneous and exothermic in nature. The method was applicable to real wastewater samples, with 99% removal of MB and MO. The results of this study show that MWMSC is an inexpensive biosorbent that is successfully utilized in removing methylene blue and methyl orange dyes from wastewater.

A simple, efficient, and rapid method for dye removal from wastewater using an IDA-GO@Fe3O4 magnetic nanocomposite.

With the rapid advancement of the dye and textile industry, there has been increasing concern regarding the contamination of wastewater with dyes and its potential influence on human health. Therefore, the removal of dye pollutants from wastewater has become a matter of significant importance. In this study, a magnetically responsive iminodiacetic acid-functionalized graphene oxide (IDA-GO@Fe3O4) nanocomposite was utilized for the adsorption of both cationic and anionic dyes. The IDA-GO@Fe3O4 nanocomposite was synthesized and thoroughly characterized using several analytical techniques such as XRD, SEM, FT-IR, TGA and BET analysis. The prepared magnetic nanocomposite had a much higher thermal stability than pure graphene oxide. The negatively charged surface of the IDA-GO@Fe3O4 magnetic nanocomposite made it an excellent candidate for removing cationic dyes. The effects of various factors, including pH, initial concentration (isotherms), amount of adsorbent, and contact time (kinetics), on adsorption efficiency were investigated. The optimal conditions for the removal of methylene blue were determined to be 0.005 g of adsorbent, a pH of 10, and a contact time of 160 minutes. In contrast, the optimal conditions for the removal of methylene orange were found to be 0.005 g of adsorbent, a pH of 2, and a contact time of 120 minutes. Experimental data shows that the adsorption capacity for MB is reported as 437.10 mg g-1 at pH 10, while for MO it is 165.65 mg g-1 at pH 2. Furthermore, the adsorption process followed a pseudo-second-order kinetic model and Langmuir isotherm model. The proposed adsorption mechanism of MB and MO dyes onto the IDA-GO@Fe3O4 nanocomposite involve various interactions, such as electrostatic interactions, H-bonding, n-π, and π-π interactions. Importantly, the IDA-GO@Fe3O4 nanocomposite exhibited outstanding recyclability, retaining its effectiveness even after five successive cycles for MB. This suggests a straightforward method for developing high-performance IDA-GO@Fe3O4 magnetic nanocomposites for efficient wastewater purification and environmental remediation applications.

Characterization of porous starch produced from edible canna (Canna edulis Kerr.) via enzymatic hydrolysis using thermostable α-amylase and glucoamylase

Porous starch (PS) with high surface areas can enhance functional properties, thereby expanding its application. The purpose of this study was to determine the effect of different types and concentrations of amylolytic enzymes on the physical, chemical, and functional characteristics of edible canna PS. Canna edulis Kerr. starch (5 g) was added with an enzyme (AM, GA or mixed) in a specific buffer, incubated at 60 °C for 8 h, then dried at 40 °C for 48 h. SEM displayed that AM, GA and mixed produced large & shallow, small & deep pores, and large & deep pores, respectively. Starch hydrolyzed by 75 U/g GA exhibited the highest swelling power and WAC (96.69 %). PS mixed had the highest solubility and MB adsorption capacity. The highest OAC of 111.21% was presented by the starch hydrolyzed by 100 U/g AM. PS could be applied as the encapsulation agents of nutrients or pigment carriers.

A comparative assessment of the methylene blue dye adsorption capacity of natural biochar versus chemically altered activated carbons

Textile wastewater improperly released damages the environment. In this research, rice straw was pyrolyzed to produce pristine biochar (biochar A) and processed with NaOH, KOH, H3PO4, and ZnCl2 to synthesize activated carbons B, C, D, and E, respectively. For all the activated carbons and biochar-A, the pseudo-second-order kinetic model and the Langmuir adsorption isotherm accurately depicted the adsorption process signifying the monolayer layer adsorption mechanism. The highest MB adsorption capacity for biochar A was noted (86.95 mg g−1). Compared to the MB dye, activated carbons, biochar A and their supernatant solutions were significantly less hazardous based on toxicity evaluations. Based on a comparison of all the activated carbons (B, C, D, and E), biochar A can be employed as an adsorbent to remove dye from textile effluent.

Three-dimensional sulfonic-functionalized porphyrin-based porous organic polymer for high-performance methylene blue and ciprofloxacin capture

The pollution of toxic organic dyes and unmetabolized antibiotics to environments was becoming increasingly serious, therefore, it was urgent to remove them. In this paper, a three-dimensional hypercrosslinked porphyrin-based porous organic polymer (TP-PPOPs) with 5,10,15,20-tetraphenylporphyrin and triptycene as monomers was designed and synthesized for the first time. By further reacting TP-PPOPs with chlorosulfonic acid, a new three-dimensional sulfonic acid functional material (TP-PPOPs-SO3H) with significantly improved electronegativity and hydrophilicity was obtained. Both reactions were mild and no expensive metal catalysts were required. Benefiting from the hypercrosslinked structure, stable three-dimensional rigid framework, abundant adsorption active sites and high specific surface area, TP-PPOPs-SO3H exhibited extremely fast adsorption rate, outstanding adsorption selectivity, extraordinary reusability and ultra-high adsorption capacity for MB and CIP, with the maximum adsorption capacities being 1283.33 mg·g−1 for MB and 485.39 mg·g−1 for CIP, respectively. The study of adsorption mechanism revealed that the ultra-high adsorption capacity of TP-PPOPs-SO3H on MB and CIP was mainly attributed to their strong electrostatic interaction and the extended π-conjugated frameworks and large specific surface area of TP-PPOPs-SO3H.

ZnO nanoparticles dispersed in nitrogen-enriched carbon matrix for the efficient adsorption and photocatalytic degradation of aqueous methylene blue molecules

In the present study, ZnO nanoparticles dispersed in graphitic carbon nitride (g-C3N4) composite is synthesized via hydrothermal route at 150 °C. The synthesized material (ZnO/g-C3N4) is further heat-treated at an optimized temperature of 500 °C in an air-rich environment and the heat-treated material is denoted as the ZnO/g-C3N4-HT. Physicochemical properties of the as-synthesized material are evaluated by various analytical and spectroscopic techniques. The obtained results confirm good dispersion of the ZnO nanoparticles on the surface of the g-C3N4. The ZnO/g-C3N4-HT is further tested for its adsorption ability and photocatalytic activity towards aqueous methylene blue (abbreviated as MB). The data show that the ZnO/g-C3N4-HT possesses remarkably high MB adsorption capacity of 251.70 mg/g at the pH value of 7. The MB adsorption capacity obtained in the present study is superior to most of the carbon-based adsorbents. The kinetic curve is found to be in good agreement with pseudo-second-order kinetic model. The remarkably high MB adsorption capacity is ascribed to the combined effects of surface area, wettability characteristic, and the negative surface charge of the material. The photocatalytic MB-degradation study over the ZnO/g-C3N4-HT yields a maximum degradation efficiency of 90% with pseudo-first-order rate constant value of 0.0113 min−1. The high MB-degradation efficiency of the material is attributed to the modified band gap and morphological properties of the material. With adequate optimization, the ZnO/g-C3N4-HT may be useful in the removal of several other recalcitrant organic pollutants from water.

Fabrication of a bio-adsorbent material by grafting CeO2 quantum dots (QDts) over Areca nut shell biochar using Saccharum officinarum extract as a solvent/capping agent for adsorption of Methylene blue dye: Synthesis, material analyses, adsorption kinetics and isotherms studies

The presence of diverse organic compounds, such as dyes, in wastewater may pose potential environmental hazards. Therefore, it is imperative to remove these harmful substances from the various water resources. In this work, the composite of Ceria (CeO2) and areca nut shell biochar (CB) were used as adsorbents to extract Methylene blue dye (MB) from synthetic effluent. The study involved conducting batch experiments to investigate the effects of various factors, including initial MB concentration, solution pH, contact time, and CB dosage, on the adsorption process. Multiple characterization techniques were employed to examine the characteristics of CB. The study identified the most optimal values of variables for the removal of MB as follows: a CB dosage of 0.5 g L−1, an initial concentration of 50 mg L−1, a pH of the solution of approximately 10, and a contact time of 75 min. These conditions resulted in a ∼ 96% efficiency in the removal of MB in 75 min. The impact of the pH of the solution on the removal of MB was found to be more substantial in comparison to the sorbate dosage. The superior effectiveness of CB in eliminating MB in comparison to ASB and CeO2 can be attributed to its porous structure and uneven surfaces, which offer numerous active sites for MB adsorption. The study determined that CB exhibited a maximum adsorption capacity for MB at a concentration of 250 mg L−1 under optimal conditions, it was 492.2 mg g−1. The pseudo-second-order model was found to be the most suitable for describing the kinetics of adsorption, whereas the adsorption isotherms were best fitted by the Freundlich equation. Thermodynamically spontaneous and endothermic physisorption of MB over CeO2 @ASB. The efficiency of MB removal remained above 93% even after undergoing five cycles of recycling. The primary processes responsible for the elimination of MB on the adsorbent were electrostatic and pi-pi interactions. The utilization of CB exhibits significant potential for the elimination of MB from polluted solutions owing to its robust adsorption capability and efficient reusability.

Cellulose Acetate/Polyethylene Glycol Composite Beads for Efficient Removal of Methylene Blue

The development of eco-friendly and biodegradable adsorbent with excellent adsorption performance is of great importance for the efficient dye removal in wastewater. Herein, an efficient and biodegradable composite adsorbent bead was fabricated from cellulose acetate (CA) modified with low molecular weight polyethylene glycol 200 (PEG200) for the adsorptive removal of methylene blue dye (MB) from aqueous solution. The weight fraction of PEG was varied to investigate the effect of material bead composition on the morphology, molecular structure, crystal phases, thermal stability, mechanical properties, and adsorption performance of the composite beads. Batch adsorption was carried out at various times to estimate the time at equilibrium adsorption capacity and kinetic model. Various operating conditions such as pH, initial MB concentration, and adsorbent dosage in experiment were also executed to examine the adsorption performance of this system. The result showed that all beads have porous structure and the pore size increase after the addition of PEG200. The adsorption capacity and % MB removal generally showed an improvement with the rise of PEG content. The batch adsorption experiments demonstrated that the best % removal and adsorption capacity of MB were 93.35 % and 28.005 mg/g, respectively, that was obtained by composite CA/PEG200 (80/20) bead at pH of 11, initial MB concentration of 30 mg/L, and bead dosage of 1 g/L. The adsorption kinetic fitted well to Elovich-kinetic model with average R2 of 0.844. Overall, this work offers new finding into the development of effective, environmentally friendly, and inexpensive cellulose-based adsorbents for wastewater remediation.

Synthesis of novel antibacterial nanocomposite CuO/Ag-modified zeolite for removal of MB dye

Novel CuO/Ag nanocomposites added zeolite (CAZ) were successfully fabricated, and their effectiveness as an antibacterial on S. aureus and MB removal was evaluated. EDX, XRD, and FTIR confirm the presence of the elemental compositions of CAZ. Friable CuO nanorods (10–70 nm in diameter) existed on the surface of the zeolite. Pure zeolite had a higher band gap (5.433 eV) and lower MB removal efficiency than CAZ. The adsorption method by CAZ was more effective at removing MB than photodegradation. 0.10 CAZ had the highest removal effectiveness (~ 99%) and adsorption capacity (~ 70.4 mg g−1) of MB. The inhibitory zone diameter for 0.005 CAZ against S. aureus was 20 mm, while 0.01 CAZ had a diameter of 17 mm. Azithromycin, ceftriaxone, and erythromycin antibiotics demonstrated lower or no efficacy against S. aureus than CAZ. Significant antibacterial activities and wastewater treatment were achieved by CAZ. The combination of photodegradation and adsorption enhanced pollutant removal. It will be interesting to study further the optimal molar ratio for MB removal (0.10 CAZ) in future investigations.

Composite aerogels of alginate/poly(acrylamide)/carbon nanotubes with enhanced performance for cationic dyes adsorption

This study presents the preparation and characterization of a composite aerogel with a double network of alginate (Alg) and poly(acrylamide) (PAM), filled with multi-walled carbon nanotubes (MWCNT). The double network structure was formed by mixing alginate and the PAM network and subsequently cross-linking the polysaccharide with Ca2+ ions. Characterization analyses demonstrated that the inclusion of MWCNT resulted in significant changes to the thermal, morphological, mechanical, and swelling properties of the composite compared to the pristine aerogel (Alg/PAM). Adsorption experiments demonstrated the effectiveness of Alg/PAM/MWCNT in removing cationic dyes (methylene blue, MB, and crystal violet, CV) from aqueous solutions. Notably, the aerogel containing MWCNT exhibited 1.5 times higher adsorption capacity for MB and CV compared to Alg/PAM under similar experimental conditions. Isothermal analyses revealed distinct adsorption behaviors for MB and CV on Alg/PAM/MWCNT, and competitive adsorption was observed when both dyes were present in the solution simultaneously. The composite aerogel also demonstrated excellent reusability, maintaining its performance for at least five cycles, indicating its potential for long-term application.

Hydrochar derived from Liquorice root pulp utilizing catalytic/non-catalytic hydrothermal carbonization: RSM optimization and cationic dye adsorption assessment

The present study targeted producing hydrochar from Liquorice root pulp employing the catalytic/non-catalytic hydrothermal carbonization (HTC) method and evaluating its performance in methylene blue adsorption from an aqueous solution. The response surface methodology (RSM) was utilized to assess the impact of operational variables such as temperature, time, and water/ solid ratio on the yield of hydrochar production and MB adsorption capacity. The maximum yield of hydrochar production and dye adsorption capacity was achieved at 168 °C, 2.016 h, and a water/solid ratio of 9.215. The assessment of the catalytic HTC process at different concentrations of ZnCl2 demonstrated the 0.25 M solution had the most positive effect on MB adsorption capacity. The physicochemical characteristics of hydrochars were evaluated utilizing techniques such as CHN, FTIR, BET, XRD, TGA, and SEM. Also, the peak fitting method presented a semi-quantitative assessment of the impact of the catalytic/ non-catalytic HTC process on the oxygenated functional groups of hydrochars. The methylene blue adsorption process was evaluated by conducting the experiments at different values of effective parameters such as pH, contact time, initial dye concentration, and dose of adsorbent as temperature. Furthermore, the kinetic and isotherm models were studied to describe the dominant mechanisms in the MB adsorption process. The maximum MB adsorption capacity was achieved at 290.65 and 314.62 mg/g for hydrochar and modified hydrochar at pH of 9, initial dye concentration of 400 mg/L, 45 min of contact time, 1 g/L of adsorbent dose, and temperature of 25 °C. Finally, studying the thermodynamic parameters of the adsorption process demonstrated MB adsorption's spontaneity and exothermic nature.