Microporous activated carbon developed from KOH activated biomass waste: surface mechanistic study of methylene blue dye adsorption

Ultrasmall copper-metal organic framework (Cu-MOF) quantum dots decorated on waste derived biochar for enhanced removal of emerging contaminants: Synergistic effect and mechanistic insight

This study proposes a novel one-pot hydrothermal impregnation strategy for surface decoration of waste derived pisum sativum biochar with zero‒dimensional Cu‒MOF Quantum dots (PBC‒HK), with an average particle size of 5.67 nm, for synergistic removal of an emerging sulfur containing drug pantoprazole (PTZ) and Basic Blue 26 (VB) dye within 80 min and 50 min of visible-light exposure, respectively. The designed Integrated Photocatalytic Adsorbent (IPA) presented an enhanced PTZ removal efficiency of 95.23% with a catalyst loading of 0.24 g/L and initial PTZ conc. 30 mg/L at pH 7, within 80 min via synergistic adsorption and photodegradation under visible-light exposure. While, on the other hand, 96.31% VB removal efficiency was obtained in 50 min with a catalyst dosage of 0.20 g/L, initial VB conc. 60 mg/L at pH 7 under similar irradiation conditions. An in-depth analysis of the synergistic adsorption and photocatalysis mechanism resulting in the shortened time for the removal of contaminants in the synergistic integrated model has been performed by outlining the various advantageous attributes of this strategy. The first-order degradation rate constant for PTZ was found to be 0.04846 min-1 and 0.04370 min-1 for PTZ and VB, respectively. Adsorption of contaminant molecules on the biochar (PS‒BC) surface can facilitate photodegradation by accelerating the kinetics, and photodegradation promotes regeneration of adsorption sites, contributing to an overall reduction in operation time for removal of contaminants. Besides enhancing the adsorption of targeted pollutants, the carbon matrix of IPAs serves as a surface for adsorption of intermediates of degradation, thereby minimizing the risk of secondary pollution. The photogenerated holes present in the VB is responsible for the generation of •OH radicals. While, the photogenerated electrons present in the CB are captured by Cu2+ of the MOF metal center, reducing it to Cu+, which is subsequently oxidized to produce additional •OH species in the aqueous medium. This process leads to effective charge separation of the photogenerated charge carriers and minimizes the probability of charge recombination as evident from photoluminescence (PL) analysis. Meanwhile, PL studies, EPR and radical trapping experiments indicate the predominant role of •OH radicals in the removal mechanism of PTZ and VB. The investigation of the degradation reaction intermediates was confirmed by HR‒LCMS, on the basis of which the plausible degradation pathway was elucidated in detail. Moreover, effects of pH, inorganic salts, other organic compounds and humic acid concentration have been investigated in detail. The environmental impact of the proposed method was comprehensively evaluated by ICP-OES analysis and TOC and COD removal studies. Furthermore, the economic feasibility and the cost-effectiveness of the catalyst was assessed to address the potential for large scale commercialization. Notably, this research not only demonstrates a rational design strategy for the utilization of solid waste into treasure via the fabrication of IPAs based on MOF Quantum dots (QDs) and waste-derived biochar, but also provides a practical solution for real wastewater treatment systems for broader industrial applications.

Mesoporous activated carbon derived from fruit by-product by pyrolysis induced chemical activation: optimization and mechanism for fuchsin basic dye removal

In this study, pineapple crown (PC) feedstock residues were utilized as a potential precursor toward producing activated carbon (PCAC) via pyrolysis induced with ZnCl2 activation. The PCAC has a surface area (457.8 m2/g) and a mesoporous structure with an average pore diameter of 3.35 nm, according to the Brunauer-Emmett-Teller estimate. The removal of cationic dye (Fuchsin basic; FB) was used for investigating the adsorption parameters of PCAC. The optimization of significant adsorption variables (A: PCAC dose (0.02-0.1 g/100 mL); B: pH (4-10); C: time (10-90); and D: initial FB concentration (10-50 mg/L) was conducted using the Box-Behnken design (BBD). The pseudo-second-order (PSO) model characterized the dye adsorption kinetic profile, whereas the Freundlich model reflected the equilibrium adsorption profile. The maximum adsorption capacity (qmax) of PCAC for FB dye was determined to be 171.5 mg/g. Numerous factors contribute to the FB dye adsorption mechanism onto the surface of PCAC, which include electrostatic attraction, H-bonding, pore diffusion, and π-π stacking. This study illustrates the utilization of PC biomass feedstock for the fabrication of PCAC and its successful application in wastewater remediation.

Removal of doxorubicin hydrochloride and crystal violet from aqueous solutions using spray-dried niobium oxide coated with chitosan-activated carbon: Experimental and DFT calculations

Spray-dried niobium oxide coated with chitosan-activated carbon (NIC) was synthesized and used to remove doxorubicin hydrochloride and crystal violet from aqueous solutions under different parameters such as solution pH (2, 4, 6, and 8), contact time (1 to 9 h), initial concentration (20 to 200 mg L-1), and competing ions (0.1 M of CaCl2 and NaCl). The addition of 5 % chitosan-activated carbon to the matrix of niobium oxide slightly increased the specific surface area from 26 to 30 m2 g-1, with the introduction of a carboxylic functional group. This led to an increase in the amount of adsorbed doxorubicin hydrochloride (DOH) from 30 to 44 mg g-1 and that of crystal violet (CV) from 15 to 32 mg g-1 from the initial respective 100 mg L-1 at pH 8. The data from the concentration study fitted into Liu isotherm having adsorption capacity of 128 and 57 mg g-1 for DOH and CV respectively, while pseudo first and second order are more suitable for adsorption kinetics. The additional functional groups on the IR spectrum of NIC after the adsorption of DOH and CV confirmed the interaction between NIC and the adsorbates' molecules. The mechanism of adsorption was supported by DFT calculations.

Surface modification of toner-based recyclable iron oxide self-doped graphite nanocomposite to enhance methylene blue and tetracycline adsorption

An innovative task was undertaken to convert ubiquitous and toxic electronic waste, waste toner powder (WTP), into novel adsorbents. Alkaline modification with KOH, NaOH, and NH4OH was employed for the first time to synthesize a series of surface-modified WTP with enhanced dispersibility and adsorption capacity. XRD, XRF, FTIR, and BET analyses confirmed that the prepared KOH-WTP, NaOH-WTP, and NH4OH-WTP were oxygen-functionalized self-doped iron oxide-graphite nanocomposites. The prepared adsorbents were used to remove methylene blue and tetracycline from aqueous solutions. KOH-WTP (0.1 g/100 mL) adsorbed 80% of 10 mg/L methylene blue within 1 h, while 0.1 g/100 mL NH4OH-WTP removed 72% of 10 mg/L tetracycline in 3 h. Exploring surface chemistry by altering solution pH and temperature suggested that hydrogen bonding, electrostatic interactions, π-π electron stacking, and pore filling were plausible adsorption mechanisms. Scanning electron microscopy revealed a diminishing adsorbents porosity after adsorption proving the filling of pores by the adsorbates. KOH-WTP and NH4OH-WTP removed 77% and 61% of methylene blue and tetracycline respectively in the fourth reuse. The adsorption data of methylene blue and tetracycline fitted the Freundlich isotherm model. The maximum adsorption capacities of KOH-WTP and NH4OH-WTP for methylene blue and tetracycline were 59 mg/g and 43 mg/g respectively. The prepared adsorbents were also compared with other adsorbents to assess their performance. The transformation of waste toner powder into magnetically separable oxygen-functionalized WTP with outstanding recyclability and adsorption capacity showcases a significant advancement in sustainable wastewater treatment. This further aligns with the principles of the circular economy through the utilization of toxic e-waste in value-added applications. Additionally, magnetic separation of surface-modified WTP post-treatment can curtail filtration and centrifugation expenses and adsorbent loss during wastewater treatment.

High surface area activated carbon from a pineapple (ananas comosus) crown via microwave-ZnCl2 activation for crystal violet and methylene blue dye removal: adsorption optimization and mechanism

In this investigation, microwave irradiation assisted by ZnCl2 was used to transform pineapple crown (PN) waste into mesoporous activated carbon (PNAC). Complementary techniques were employed to examine the physicochemical characteristics of PNAC, including BET, FTIR, SEM-EDX, XRD, and pH at the point-of-zero-charge (pHpzc). PNAC is mesoporous adsorbent with a surface area of 1070 m2/g. The statistical optimization for the adsorption process of two model cationic dyes (methylene blue: MB and, crystal violet: CV) was conducted using the response surface methodology-Box-Behnken design (RSM-BBD). The parameters include solution pH (4-10), contact time (2-12) min, and PNAC dosage (0.02-0.1 g/100 mL). The Freundlich and Langmuir models adequately described the dye adsorption isotherm results for the MB and CV systems, whereas the pseudo-second order kinetic model accounted for the time dependent adsorption results. The maximum adsorption capacity (qmax) for PNAC with the two tested dyes are listed: 263.9 mg/g for CV and 274.8 mg/g for MB. The unique adsorption mechanism of MB and CV dyes by PNAC implicates multiple contributions to the adsorption process such as pore filling, electrostatic forces, H-bonding, and π-π interactions. This study illustrates the possibility of transforming PN into activated carbon (PNAC) with the potential to remove two cationic dyes from aqueous media.

Sustainable oil palm trunk fibre based activated carbon for the adsorption of methylene blue

Activated carbon (AC) is becoming the limelight due to its widespread application as an adsorbent for wastewater treatment, gases, and catalysis. However, its high consumption and price have drawn more attention to the sustainable use of natural resources as precursor for AC production. This study focuses on synthesising AC from two types of oil palm trunk (OPT) fibres, a significant agricultural waste products produced by Malaysia's thriving palm oil industries. The BET surface area of about 2057.9 m2 g-1 was achieved by chemical activation with phosphoric acid (H3PO4). The efficiency of the synthesised AC was critically analysed based on the adsorption experiments with methylene blue (MB) by varying several parameters (dosage of adsorbent, pH, initial dye concentration, and temperature of the solution) to elucidate the adsorption mechanism(s). A maximum adsorption capacity of 320.4 mg g-1 at 50 °C was achieved, and the Temkin (r2 = 0.98, 0.95, 0.95) and Langmuir (r2 = 0.94, 0.93, 0.95) isotherm models fitted the adsorption process better than the Freundlich (r2 = 0.95, 0.90, 0.86) model. Besides, the pseudo-second-order model (r2 > 0.90) best described the adsorption process, favouring chemisorption over physisorption. Thermodynamics showed MB adsorption on AC was spontaneous except at the highest dye concentration. It was exothermic at lower dye concentrations (50 and 100 mg L-1) and endothermic at higher ones (300, 500, and 700 mg L-1). In a nutshell, this study reveals that OPT fibre is a promising precursor for synthesising highly porous AC for the adsorption of MB dye.

Gelatin aerogel with good mechanical properties and adjustable physical properties for boron adsorption from salt lake brines: An optimized process

A composite aerogel with good mechanical properties and adjustable physical properties was synthesized by a sol-gel technique on the base of gelatin for the boron adsorption from water solution. The adsorption key variables, for instance, initial boron concentration (C0) (900-1100 mg/L), the contact time (t) (8-9 h), and pH (9-11), were optimized using central composite design to obtain improved boron adsorption performance of epichlorohydrin-modified gelatin (EMG)/N-methyl-d-glutamine (NMDG) aerogel loaded with hydroxylated carbon nanotubes (EMG@NMDG). The adsorption followed the pseudo-second-order and Freundlich model. At pH of 10, C0 of 1000 mg/L and t of 10 h, the largest adsorbed amount of EMG@NMDG was 85.79 mg/g. Regeneration experiments were carried out by eluting the adsorbent using HCl. The analysis showed that the adsorption in actual brine was 62.65 mg/g. Therefore, the developed EMG@NMDG aerogel has potential value for the boron extraction from brine and wastewater.

Pristine wild sugarcane (Saccharum spontaneum) as a biosorbent for removal of methylene blue from wastewater: isotherm, kinetics and regeneration studies

Saccharum spontaneum, popularly known as Kashful (KF) is a seasonal perennial grass with thin culms, mostly an abundantly growing shrub during the autumn season in southern Asia. It is used as no-cost scavenger to convincingly arrest methylene blue, a recalcitrant dye from colored effluent. FTIR, FESEM-EDX, and BET surface area characterize the material well whereas the surface activity was evaluated from zero-point charge (pHZPC = 6.720). FTIR highlights the presence of polyphenolic and carboxylate moieties. The surface texture is rod-like with intermittent non-homogeneous pores with occasional fractures. The equilibrium reaches within 60 min with the maximum adsorption capacity of 20.917 mg/g. The fibrous powder of kashful stalk (KFS) follows pseudo-second-order (R2 = 0.999 for linear and R2 = 0.985 for non-linear) kinetics and both Langmuir and Freundlich isotherm model (for linear, Langmuir R2=0.995; for non-linear, R2 = 0.994 for both Langmuir and Freundlich model). The uptake process was spontaneous (ΔG= -3.077 kJ/mol) and endothermic (ΔH = 17.815 kJ/mol). 1:1 methanol could regenerate the dye-loaded material in up to 55% and onward efficiency was conducive for three consecutive cycles. Industrial effluent analysis suggests a real-time removal of ∼55% in the first cycle. Saccharum spontaneum could be exercised to solve environmental problems related to colored water.

Application of carbon from pomegranate husk for the removal of ibuprofen, cadmium and methylene blue from water

The presence of pharmaceutical products, dyes, and toxic metal ions in water is a major problem worldwide. This work developed low-cost pomegranate-based materials to uptake ibuprofen, cadmium and methylene blue from water. Pomegranate husks (PPH) were carbonized at 400 °C to form carbonized pomegranate husk (CPH), and nanoparticles were loaded into the carbon surface (NPH) by co-precipitation. SEM micrographs showed that the morphology of carbon was highly porous compared to pristine pomegranate husk. The data for BET revealed that CPH and NPH, had about a 20-fold increase in surface area of 142 m2/g and 190 m2/g respectively compared with 9.27 m2/g for PPH. The composites exhibited larger pore sizes and volumes. TEM images confirmed the loading of nanoparticles. The FTIR results showed that the materials had on their surface oxygenated groups such as -OH, -C]O, -COC and other groups like -NH and -C]C which are anticipated to play an essential role in the sorption of the pollutants. It was found that removal efficiency increased when there was a progressive increase in pollutant concentration for all adsorbents. The best pH value of the solution for the sorption processes was pH 8. The recorded adsorption capacities at pH 8 for Cd(II), IBU and MB were 92.85, 39.77 and 95.89 mg/g for NPH, 72.60, 32.58 and 80.59 mg/g for CPH and 32.78, 16.12 and 40.79 mg/g for PPH. Contact time studies showed three sorption steps. Step 1: rapid increase at the initial stage. Step 2: marginal uptake. Step 3: plateau. The trends indicated that sorption was influenced by temperature variation. The data for the thermodynamic parameter △Ho suggest that all the sorption processes were endothermic; the obtained positive values indicate this. The △Ho for PPH was between (64.33-69.08 kJ/mol), 82.84-86.03 kJ/mol for CPH and 87.17-88.96 kJ/mol for NPH. For PPH, molecular interactions were physisorption, and chemisorption for CPH and NPH. The △So has positive values, showing increased freedom during the sorption. The adsorbents followed PSO based on uptake processes involving syngenetic mechanisms.

Kinetics and Thermodynamics Study of Methylene Blue Adsorption to Sucrose- and Urea-Derived Nitrogen-Enriched, Hierarchically Porous Carbon Activated by KOH and H3PO4

Hierarchically porous nitrogen-enriched carbon materials synthesized by polymerization of sucrose and urea (SU) were activated by KOH and H₃PO₄ (SU-KOH and SU-H₃PO₄, respectively). Characterization was undertaken and the synthesized materials were tested for their ability to adsorb methylene blue (MB). Scanning electron microscopic images along with the Brunauer-Emmett-Teller (BET) surface area analysis revealed the presence of a hierarchically porous system. X-ray photoelectron spectroscopy (XPS) confirms the surface oxidation of SU upon activation with KOH and H₃PO₄. The best conditions for removing dyes utilizing both activated adsorbents were determined by varying the pH, contact time, adsorbent dosage, and dye concentration. Adsorption kinetics were evaluated, and the adsorption of MB followed second-order kinetics, suggesting the chemisorption of MB to both SU-KOH and SU-H₃PO₄. Times taken to reach the equilibrium by SU-KOH and SU-H₃PO₄ were 180 and 30 min, respectively. The adsorption isotherm data were fitted to the Langmuir, Freundlich, Temkin, and Dubinin models. Data were best described by the Temkin isotherm model for SU-KOH and the Freundlich isotherm model for SU-H₃PO₄. Thermodynamics of the adsorption of MB to the adsorbent was determined by varying the temperature in the range of 25-55 °C. Adsorption of MB increased with increasing temperature, suggesting that the adsorption process is endothermic. The highest adsorption capacities of SU-KOH and SU-H₃PO₄ (1268 and 897 mg g^-1, respectively) were obtained at 55 °C. Synthesized adsorbents were effective in removing MB for five cycles with some loss in activity. The results of this study show that SU activated by KOH and H₃PO₄ are environmentally benign, favorable, and effective adsorbents for MB adsorption.

Synergistic effect of hydrogen bonding and π-π interaction for enhanced adsorption of rhodamine B from water using corn straw biochar

Dyes adsorption to biochar via hydrogen bonding, and π-π interaction alone have attracted much research attention, however, their synergism in adsorption mechanisms remains largely unnoticed. The synergistic effects of the hydrogen bonding and π-π interaction might improve the adsorption capacity and need more understanding to prepare high-capacity biochar. In this work, we evaluated the adsorption of various dyes on biochar prepared via the activation of potassium bicarbonate and urea (named BC-KN) to explore their synergistic effects. Batch experiments indicated the BC-KN showed a high adsorption capacity to rhodamine B at 4839.0 mg/g, azure B at 4477.7 mg/g, and methylene blue at 2223.0 mg/g, respectively. The mechanism of such significant adsorption was investigated by their comparative experiments, characterizations, and computational analyses. The computational analyses suggested that the synergism of the hydrogen bonding and π-π interaction improves the adsorption energies of BC-KN/RhB system from -10.35 kcal/mol to -20.49 kcal/mol. It can be concluded that the hydrogen bonding and π-π interaction can synergize to significantly improve the adsorption by increasing the π-electron density and shortening the distance of aromatic rings, thus dyes with H-donor show significantly better adsorption capacities. The insight of hydrogen bonding being the governing factor in the synergistic system will help produce high-capacity biochar in removing aromatic dyes and suggest a sustainable technology for the efficient decolorization of dye effluent to minimize its damage to the health and environment.

Effective decontamination of methylene blue from aqueous solutions using novel nano-magnetic biochar from green pea peels

The conversion of agricultural waste into high-value carbon products has been an attractive area in waste management strategy. This study highlighted the synthesis and effectiveness of green pea peels (GPP), green pea biochar (GPBC), and nano-ferromagnetic green pea biochar (NFGPBC) by the ferrous/ferric co-precipitation synthesis method for eliminating cationic dyes molecules from solutions. The morphological, physicochemical, and structural properties of GPP, GPBC, and NFGPBC were approved by Scanning Electron Microscopy (SEM), Transmission Emission Microscopy (TEM), Energy Dispersive X-ray (EDX), Bruneau Emmett Teller (BET), Fourier Transform Infrared spectroscopy (FTIR), and X-ray Diffraction (XRD) techniques. Vibrating Sample Magnetometry (VSM) analysis confirmed the NFGPBC magnetization performance. The capacity of each adsorbent for methylene blue removal was evaluated at various parameters of material dosage (50-250 mg/150 mL), pH (2-12), initial concentration (50-250 mg/L), contact time (0-90 min) and temperature (20-60 °C). The three developed adsorbent materials GPP, GPBC, and NFGPBC, possessed reasonable BET surface areas of 0.6836, 372.54, and 147.88 m2g-1, and the corresponding monolayer adsorption capacities of 163.93, 217.40, and 175.44 mg/g, respectively. The superior performances of GPBC and NFGPBC were due to their increased surface area compared with the parent green pea peels (GPP). The results from adsorption kinetics studies of all prepared materials were pseudo-second-order and Elovich kinetics models. The thermodynamic parameters exhibited MB sorption's favorability, spontaneity, and endothermic nature. The NFGPBC material experienced Vander Waal forces, electrostatic interaction, hydrogen bonding, and hydrophobic interactions as predominant modes of the solid-liquid interaction. The regeneration, recycling, and reusability of the synthesized GPP, GPBC, and NFGPBC performed at five adsorption cycles revealed that NFGPBC demonstrated excellent cyclical performances attaining a minimum 8.9% loss in capacity due to paramagnetic properties. Thus, NFGPBC is a green, efficient, and eco-friendly material recommended for large-scale production and application in wastewater.

Tropical fruit wastes including durian seeds and rambutan peels as a precursor for producing activated carbon using H3PO4-assisted microwave method: RSM-BBD optimization and mechanism for methylene blue dye adsorption

Herein, tropical fruit biomass wastes including durian seeds (DS) and rambutan peels (RP) were used as sustainable precursors for preparing activated carbon (DSRPAC) using microwave-induced H3PO4 activation. The textural and physicochemical characteristics of DSRPAC were investigated by N2 adsorption-desorption isotherms, X-ray diffraction, Fourier transform infrared, point of zero charge, and scanning electron microscope analyses. These findings reveal that the DSRPAC has a mean pore diameter of 3.79 nm and a specific surface area of 104.2 m2/g. DSRPAC was applied as a green adsorbent to extensively investigate the removal of an organic dye (methylene blue, MB) from aqueous solutions. The response surface methodology Box-Behnken design (RSM-BBD) was used to evaluate the vital adsorption characteristics, which included (A) DSRPAC dosage (0.02-0.12 g/L), (B) pH (4-10), and (C) time (10-70 min). The BBD model specified that the DSRPAC dosage (0.12 g/L), pH (10), and time (40 min) parameters caused the largest removal of MB (82.1%). The adsorption isotherm findings reveal that MB adsorption pursues the Freundlich model, whereas the kinetic data can be well described by the pseudo-first-order and pseudo-second-order models. DSRPAC exhibited good MB adsorption capability (118.5 mg/g). Several mechanisms control MB adsorption by the DSRPAC, including electrostatic forces, π-π stacking, and H-bonding. This work shows that DSRPAC derived from DS and RP could serve as a viable adsorbent for the treatment of industrial effluents containing organic dye.

Adsorption of crystal violet on activated bamboo fiber powder from water: preparation, characterization, kinetics and isotherms

Biomass-activated carbon has made a great contribution as an adsorbent in the field of dye wastewater treatment. In this study, the response surface method (RSM) based on the Box-Behnken design was used to optimize the preparation process. Bamboo fiber activated carbon (BAC) with a specific surface area of 2892 m² g^-1 and a pore volume of 1.80 cm³ g^-1 was prepared. Various characterization methods (SEM, XPS, XRD, and Raman spectroscopy) were used to analyze the micro-structure of BAC. In the microscopic state, the BAC is fibrous and maintains the originally connected pores of the bamboo fiber. After high-temperature activation, the microcrystallinity of BAC decreases, and the degree of graphitization is low, indicating the presence of amorphous carbon. The adsorption capacity of BAC to crystal violet in simulated wastewater was evaluated via an adsorption experiment. Under the following conditions: the dosage of BAC was 0.04 g, the concentration was 600 mg L^-1, the adsorption temperature and time were 25 °C and 30 min, respectively, and the as-prepared BAC had a 99.96% removal rate. The adsorption process conformed to the pseudo-second-order kinetic model and Langmuir adsorption isotherm model, indicating that the adsorption process of CV on BAC belonged to monomolecular layer adsorption. The adsorption process occurs spontaneously and is accompanied by heat release, and the maximum adsorption capacity of BAC within a given concentration range could reach 1353.09 mg g^-1. SEM-EDS characterization before and after adsorption showed that ion exchange and the presence of oxygen-containing functional groups played an important role in promoting the adsorption process. The results show that BAC considerably affects CV removal, which has great application prospects.

High-Surface-Area-Activated Carbon Derived from Mango Peels and Seeds Wastes via Microwave-Induced ZnCl2 Activation for Adsorption of Methylene Blue Dye Molecules: Statistical Optimization and Mechanism

In this study, Mango (Mangifera indica) seeds (MS) and peels (MP) seeds mixed fruit wastes were employed as a renewable precursor to synthesize high-surface-area-activated carbon (MSMPAC) by using microwave-induced ZnCl₂ activation. Thus, the applicability of MSMPAC was evaluated towards the removal of cationic dye (methylene blue, MB) from an aqueous environment. The key adsorption factors, namely A: MSMPAC dose (0.02–0.1 g), B: pH (4–10), and C: time (5–15 min), were inspected using the desirability function of the Box-Behnken design (BBD). Thus, the adsorption isotherm data were found to correspond well with the Langmuir model with a maximum adsorption capacity of (232.8 mg/g). Moreover, the adsorption kinetics were consistent with both pseudo-first-order and pseudo-second-order models. The spontaneous and endothermic nature of MB adsorption on the MSMPAC surface could be inferred from the negative ∆G° values and positive value of ∆H°, respectively. Various mechanisms namely electrostatic forces, pore filling, π-π stacking, and H-bonding govern MB adsorption by the MSMPAC. This study demonstrates the utility of MS and MP as renewable precursors to produce high-surface area MSMPAC with a potential application towards the removal of cationic organic dyes such as MB.

Facile preparation of sisal-Fe/Zn layered double hydroxide bio-nanocomposites for the efficient removal of rifampin from aqueous solution: kinetic, equilibrium, and thermodynamic studies

In the present study, sisal-Fe/Zn LDH bio-nanocomposite for efficiently removing rifampin was synthesized using a simple co-precipitation method. SEM, XRD, and FTIR analyses were applied to characterize the prepared composite. In the following, different factors that are affecting the adsorption of rifampin, including contact time, initial rifampin concentration, adsorbent dosage, and temperature were evaluated. Also, the kinetic, isotherm, and thermodynamic studies were investigated. The results indicated that Freundlich (R² = 0.9976) was a suitable model for describing the adsorption equilibrium and adsorption kinetic showed that the data are in maximum agreement with the pseudo-second-order kinetic model (R² = 0.9931). According to the Langmuir isotherm model, the maximum adsorption capacity of rifampin was found to be 40.00 mg/g. The main mechanisms for rifampin elimination were introduced as electrostatic attraction and physical adsorption. Moreover, the spontaneity and nature of the reaction were analyzed by elucidating thermodynamic factors that indicated the adsorption process was exothermic and spontaneous. Also, the batch process design indicated that for treating 10 L wastewater containing 100 mg/L rifampin with a removal efficiency of 96%, the needed amount of sisal-Fe/Zn LDH is 51.6 g. This study revealed that the sisal-Fe/Zn LDH bio-nanocomposites as a low-cost adsorbent have promising adsorption potential.

Pyrolysis of rubber seed pericarp biomass treated with sulfuric acid for the adsorption of crystal violet and methylene green dyes: an optimized process

In this study, the biomass of rubber seed pericarp was first treated with sulfuric acid and then its activated carbon was formed by the pyrolysis process. As produced acid-treated activated carbon of chosen biomass was then used for the adsorption of crystal violet (CV) and methylene green (MG) from the colored aqueous solution. The adsorbent was exposed to several characterization methods to know its structural and morphological behaviors before and after CV and MG adsorption. The adsorbent was found to be mesoporous having a surface area of 59.517 m²/g. The effect of pH, time, and concentration was assessed while various isotherm and kinetics models were employed to know the adsorption insight. The optimum conditions were at pH 8, within 30 min, 50 mg/L concentration, and 0.06 gm dose. The adsorption data (the maximum adsorption capacity for CV and MG were found to be 302.7 and 567.6 mg/g, respectively) was validated by fitting in a response surface statistical methodology and the positive interactions between the studied factors were found. The adsorption was mainly belonging to the electrostatic attraction of the dye molecules. The study proves that the used adsorbent is economical and an excellent source of treating wastewater.

High adsorption capacity of phenol and methylene blue using activated carbon derived from lignocellulosic agriculture wastes

The resources of clean water worldwide are very limited, and climate change is already affecting the available supplies. Therefore, developing a low-cost, highly efficient, and recyclable adsorbent to upgrade water quality has become an essential task. Herein, we report the fabrication of activated carbon (AC) adsorbents derived from lignocellulosic wastes. Both physical and chemical activation were investigated to modify the surface texture properties. The results indicated that increasing the activation temperature, whether physically or chemically, increases the specific surface area (SBET). On the contrary, increasing the amount of the chemical activating agent significantly decreases the SBET values. The SBET of 1771, 2120, and 2490 m2 g-1 were obtained for water vapor, K2CO3 and KOH, at activation temperatures of 950 °C, 800 °C, and 800 °C, respectively. Methylene blue (MB) and phenol were used as adsorbates for the adsorption experiment. Adsorption of methylene blue dye revealed the ability of the water activated carbon to remove more than 95% of the dye (100 ppm) within 5 min with an adsorption capacity of 148.8 mg g-1. For phenol adsorption, Several parameters were investigated, including initial concentration (50-250 ppm), pH (2-10), contact time (5-60 min), and temperature (25-45 °C). The highest adsorption capacity of phenol achieved was 158.9 mg g-1. The kinetics of adsorption of phenol was better described by pseudo-second-order reaction while the isotherm process using Langmuir model. This study presents a roadmap for conversion of lignocellulosic biomass waste into highly efficient porous carbon adsorbents.