Pseudo-second Order Kinetic Model Research Articles

Novel kapok pods (Ceiba pentandra (l.) Gaerth) adsorbent and its reusability by transformation on hydrochar with an outstanding adsorptive capacity for Rhodamine B removal

Among the residual biomasses, it can be cited the kapok capsule from Ceiba pentandra (L.) Gaerth, which to this date does not have any application described in the literature. Hence, the present work aims to evaluate the kapok capsule as an adsorbent to remove Rhodamine B dye from aqueous solutions. The material was characterized by SEM, OM, FTIR, XRD, pHPZC and TGA/DTG. The adsorptive performance was evaluated by kinetics, adsorbent mass, adsorbate concentration, aqueous matrix, pH and fixed-bed column. Furthermore, a destination to the material as a hydrochar was proposed, which can also be employed as adsorbent or as part of a soil compost. The morphology of the kapok pod exhibits several pores and functional groups characteristics of lignocellulosic material. The adsorption assays showed strong interactions at natural pH, with a minimal of 71 % RhB removal in batch test, best fitted to a pseudo-second order kinetic model, and, even when using real water under the most severe conditions applied, RhB removal was superior to 59 %. In the fixed bed assays, the overall removal of the pollutant was higher than 54 %. The hydrochar prepared from the residual adsorbent – kapok pod used in the previous adsorption tests – remarkably presented an even higher adsorptive capacity, removing a minimum of 92 % of dye at natural pH. In addition to this exceptional adsorption result, the application of the product to soil did not show acute toxicity towards tomato seeds, which makes the production of hydrochar an excellent alternative to the destination of the kapok pod.

Biochar derived from coffee grounds with molybdenum disulfide composites for Cr (VI) removal from wastewater

Discharging pollutants containing toxic metal ions has become a global problem, and improper disposal of coffee grounds can also cause environmental pollution. In this work, 1T-MoS2@STC (Solvothermal Carbonization, STC) was prepared from coffee grounds and molybdenum disulfide by a one-step solvothermal method that is simple in operation, low in energy consumption and low in cost, which possesses efficient adsorption of Cr (VI) in wastewater. The 1T-MoS2@STC was characterized by SEM, TEM, XRD, XPS, Zeta potential, FTIR, and BET analyses. The results showed that MoS2 was successfully loaded on coffee grounds. According to the pseudo-second order (R2 = 0.99) kinetics model, chemisorption was the main cause of adsorption. The adsorption process followed the Langmuir (R2 = 0.99) isothermal model, and the maximum adsorption capacity was 795.17 mg/g. The adsorption mechanism can be attributed to electrostatic interaction, redox reaction between Cr (VI) and active sites, and chelation between Cr (III) and hydroxyl. When 1T-MoS2@STC was applied to the treatment of actual water samples, the removal rate was also maintained at a high level (90%). In addition, 1T-MoS2@STC can maintain long-term stability (90 days) and low leaching of molybdenum (<3 mg/L) in wastewater. Therefore, in the treatment of chromium-containing wastewater, the 1T-MoS2@STC composite material simultaneously exhibited significant adsorption capacity, high interference resistance, stability and low leaching rate. This study provides a new efficient and stable Cr (VI) adsorbent and promotes the practical application of MoS2 biomass derivatives composites in water purification.

Selective removal of phosphate by magnetic NaCe(CO3)2/Fe3O4 nanocomposites: Performance and mechanism

Phosphorus (P) contamination has become a worldwideissuedue to its adverse impacts on water security and human health. Additional research is required because the selectivity and adsorption capacity of P adsorbents continue to impede their practical application. Herein, a novel NaCe(CO3)2/Fe3O4 nanocomposite (NCF) with good magnetic properties were synthesized through a modified hydrothermal method for P removal from water. With an adsorption capacity of 86.69 mg P g−1, the NCF demonstrates outstanding phosphate uptake efficiency. At low P concentrations, the removal rate exceeded 90.0%, and the residual P concentration was below 0.1 mg P L−1. Notably, NCF demonstrated exceptional P selectivity in actual water containing multiple substances, with negligible interference from competing ions and humic acid (HA). The adsorption processes of NCF were well described by the pseudo-second-order kinetic model (PSO) and Langmuir isotherm model, corresponding to its kinetics and thermodynamics, respectively. The exhausted NCF can be regenerated and retain an effective phosphorus removal capability even after regeneration. Characterization results demonstrated that electrostatic attraction and ligand exchange were responsible for P adsorption, forming stable CePO4 crystals with low solubility. Moreover, the NCF demonstrated some efficacy in removing typical organic and inorganic phosphorus.

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.

Adsorption of Phosphate from Aqueous Solution by Calcination of Silicified Coal: Kinetic and Isotherm Studies

Silicified coal (SC) consisting of SiO2 is promising raw material for adsorbent. The present study aimed to utilize the adsorbent of silicified coal bottom ash (SCBA) by calcination of the SC at the temperature of 600, 800 and 1000 oC for 1 hour. The FTIR result showed that the SCBA-600, SCBA-800 and SCBA-1000 had chemical functional groups such as the asymmetric Si-O-Si, the symmetric Si-O-Si and Si-O-Si bond rocking for adsorption of phosphate (PO43−) with the lowest percentage of transmittance of SCBA-1000. The adsorption test showed that a rapid adsorption occurred in the first 10-min of contact time, and it did not change significantly for the rest of contact time until reaching an equilibrium time of 30 min. The PO43− adsorption efficiency and capacity fluctuated over initial PO43− in solution in the range of 60.02–480.29 mg/L. The highest PO43− adsorption efficiency and capacity was at 480.29 mg/L, which was 95.49 % and 45.86 mg/g, respectively using the SCBA-1000. The adsorption kinetic fitted better to pseudo second-order kinetics model (average R2 = 0.999) with the adsorption capacity of 45.454, 45.662 and 45.872 for the SCBA_600, SCBA_800 and SCBA_1000, respectively, and the PO43− adsorption rate was 0.0007, 0.0008 and 0.001 g/mg.min, respectively. The adsorption isotherm followed Langmuir model (average R2 = 0.873) with the adsorption capacity being 2.357, 1.198 and 8.196 mg/g, respectively, and the pore volume being 0.0316, 0.0364 and 0.2103 L/mg, respectively

Mass transfer process in the removal of Congo Red (CR) onto Natural Clay (NC): Kinetic, isotherm modeling, and thermodynamic study

Abstract Industrial growth and technological advancement have led to the worldwide introduction of pollutants of diverse nature into water bodies including pollutants such as dyes and organic contaminants. Their presence in industrial effluents or drinking water is a public health problem. The aim of this study was to evaluate the adsorption of Congo Red (CR) onto Natural Clay (NC) realized in a batch system. The effects of contact time, initial pH, stirring speed, temperature, adsorbent dose, and initial CR concentration on the adsorption capacity were investigated. The NC was characterized by the FTIR, DRX, BET, and point of zero charge. The experimental isotherm data follow well the Langmuir equation, providing a better fit of the equilibrium adsorption data. Under optimized conditions, up to 212.766 mg/g at 25 °C is removed from the solution. The adsorptions kinetics were found to follow rather a pseudo second-order kinetic model with a determination coefficient (R2) of 0.999. The adsorption isotherms at different temperatures have been used for the determination of thermodynamic parameters, i.e., the negative free energy ΔG0 (10.081 to 1.087 kJ/mol), positive enthalpy change ΔH0 Q5 (64 = 175 kJ/mol) values indicate that the overall CR adsorption is spontaneous and endothermic in nature.

One-Step Fabrication of Magnetic Polymer/Montmorillonite Adsorbent for Highly Efficient Phenol Adsorption

AbstractPhenol contaminants are highly biotoxic and have become a global problem threatening the environment and human health. The objective of the present study was to develop a very efficient and easily recyclable adsorbent to remove phenol. A magnetic montmorillonite composite with organic co-intercalation was fabricated by a simple one-step co-precipitation method and exhibited excellent phenol removal. Two surfactants, cetyltrimethylammonium bromide (CTAB) and erucic acid amide (EA), were successfully co-intercalated into the interlayer of Ca-montmorillonite, and Fe3O4 nanoparticles were simultaneously decorated to obtain Fe3O4-CTAB/EA-montmorillonite composite (Fe3O4-C/E-Mnt). The morphology and structure of Fe3O4-C/E-Mnt composite were explored by using different techniques such as X-ray diffraction, Fourier-Transform infrared spectroscopy, X-ray photoelectron microscopy and so on. The adsorption capacity of Fe3O4-C/E-Mnt for phenol was investigated under various conditions including temperature, pH, contact time, various phenol concentrations, and adsorbent dosage. The results showed that Fe3O4-C/E-Mnt retained a lamellar structure of Ca-Mnt with mesopores. Its interlayer space, surface area, and pore volume were increased. The Fe3O4-C/E-Mnt composite exhibited a good adsorption capacity (31.45 mg·g–1) for phenol with a removal efficiency of 85.46% at optimized conditions. Moreover, the adsorbent still maintained 78.32% of the adsorption capacity after five cycles. The adsorption test data of Fe3O4-C/E-Mnt followed the pseudo-second order kinetic model and the Langmuir model. The adsorption was a spontaneous, exothermic, entropy-decreasing process, and a possible adsorption mechanism of Fe3O4-C/E-Mnt was finally proposed.

Valorization of fly ash as zeolite by hydrothermal process for dyes adsorption

Valorization of fly ash as zeolite is one of sustainable ways to reduce environmental burden. In this paper, zeolite was prepared from fly ash by hydrothermal process and applied as dyes adsorbent. In hydrothermal process, fly ash was reacted with 5 N NaOH solution using solid/liquid ratio of 1/30 for 15 hours at temperature of 85°C. Characterization of hydrothermal products consisted of X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) surface area, and scanning electron microscope (SEM) analysis. The results indicated the formation of Na-X zeolite with higher surface area compared to raw fly ash. The obtained zeolite was applied as Eriochrome Black-T (EBT) dye adsorbent. Adsorption was conducted in batch process with variations in time and dye initial concentration. The adsorption efficiency would increase with increasing time, but after 90 minutes the adsorption efficiency would be relatively constant. The higher the dye initial concentration, the lower the adsorption efficiency. Furthermore, the study of adsorption kinetics model and adsorption isotherm model that had been carried out showed that adsorption process of EBT dye by zeolite from fly ash tended to follow pseudo-second order kinetics model and Freundlich isotherm model.

Novel adsorbent for malachite green from okra stalks waste: synthesis, kinetics and equilibrium studies

In this study, malachite green (MG) removal was performed with activated carbon synthesized from okra stalks by microwave assisted chemical activation method. In the synthesis of activated carbon, the effects of gas in the microwave, activation, and impregnation rate were investigated. The synthesized activated carbon characterization was investigated using BET, FT-IR, and SEM analyses. The activated carbon surface area achieved was 759.453 m2 g−1. In addition, the surface area of activated carbon synthesized using the conventional method was17.766 m2 g−1. The effect of the initial solution concentration on MG adsorption was investigated. According to the kinetic and equilibrium data, it was found that the adsorption process best fitted the pseudo-second order kinetic model and the Langmuir isotherm. According to the equilibrium data, the maximum adsorption capacity (q max) of the monolayer was 119.05 mg g−1. In addition, MG adsorption was investigated by the experimental design method. The adsorption capacity at the determined optimum conditions was 99.63 mg g−1. All results show that activated carbon synthesized from waste biomass by combining the conventional method with microwave-assisted impregnation is a cheap and environmentally friendly adsorbent.

Biosorption of Cu (II) and Pb (II) ions using acid modified Senna tora pods with a focus on isotherms and kinetics studies

The removal of heavy metals by biosorption method using agricultural waste and plant materials has become a powerful technology that is been explored for the treatment of domestic and industrial waste water due to its easy operating requirements and low cost. This work reports the application of Senna tora pods for the elimination of heavy metals (Cu and Pb ions) by biosorption in batch system. The effects of pH, contact time, dosage and initial concentration were evaluated. The kinetic and isotherms models for the Cu(II)/Pb(II) biosorption were tested basically by the pseudo-first-order and pseudo-second order kinetic models. Langmuir, Freundlich and Temkin isotherms models have also been used to fit equilibrium adsorption data. The monolayer sorption capacity (qL) of Cu(II) was found to be 0.791 mg/g while that of Pb(II) was 0.51 mg/g.The low Langmuir constant (KL) values suggests that the adsorption process was largely due to physisorption mechanism. The adsorption kinetics follow a pseudo-first-order model for Cu(II) and pseudo-second-order model for Pb(II), and the equilibrium data is suitably fitted by the Langmuir models than the Freundlich due to the high R2 values of 0.989 and 0.97 for Cu(II) and Pb(II) ions respectively. Consequently, there exists a closeness of the calculated sorption capacity (qcal) to the experimental sorption capacity (qex). In conclusion, the study generally showed that Senna tora pods is a potential and efficient adsorbent that could be explore for the bioremediation of heavy metal contaminated industrial wastewater.

Adsorption removal properties of β-cyclodextrin-modified pectin on cholesterol and sodium cholate

A novel adsorbent β-cyclodextrin-modified pectin was synthesized for removing cholesterol and bile salts from the gastric-intestinal passage. Different amounts of β-cyclodextrin were cross-linked to pectin by aldol condensation reaction via glutaraldehyde. The prepared β-cyclodextrin-modified pectins were successfully confirmed by characterization, showing a higher specific surface area and improved thermal stability with satisfactory cellular compatibility. The introduction of β-cyclodextrins dramatically improved the cholesterol adsorption capacity of pectin due to their hydrophobic cavities. Meanwhile, the modified pectins exhibited superior adsorption for sodium cholate than β-cyclodextrin or pectin itself, which was attributed to hydrophobic interactions. P10:1 displayed the strongest adsorption performance, with a maximum adsorption ability of 44.21 mg/g for cholesterol and 21.38 mg/g for sodium cholate. Furthermore, their adsorption favored the Langmuir isotherm model and pseudosecond-order kinetic model. These results indicate that modified pectin has potential as a nature-based adsorbent for removal of cholesterol and bile salts in the health food industry.

Evaluation of Effective Composite Biosorbents Based on Wood Sawdust and Natural Clay for Heavy Metals Removal from Water.

Bentonitic clay and wood sawdust are natural materials widely available in nature at low cost with high heavy metals sorption properties that, in this work, were combined to achieve an effective composite biosorbent with high sorption properties and enhanced mechanical stability. Pine, aspen, and birch wood sawdust, as well as different bentonite clays and different sawdust modification methods (H3PO4 or HCl) were used for preparing new composite biosorbents. A mixture of wood sawdust and bentonite in a ratio of 2:1 was used. All materials were characterized by using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscope (SEM) methods and tested for Cu and Ni ions removal from water. The adsorption process for all composite biosorbents was well described from a pseudo-second order kinetic model (R2 > 0.9999) with a very high initial adsorption rate of Cu and Ni ions and a maximum uptake recorded within 2 h. The results have shown that the adsorption capacity depends mainly on the kind of wood and the acid treatment of the wood that enhances the adsorption capacity. At a concentration of 50 mg/L, the biosorbent prepared using birch wood sawdust showed the worst performance, removing barely 30% of Cu and Ni ions, while aspen wood sawdust improved the adsorption of Cu (88.6%) and Ni (52.4%) ions. Finally, composite biosorbent with pine wood sawdust showed the best adsorption be haviour with an efficiency removal of 98.2 and 96.3% of Cu and Ni ions, respectively, making it a good candidate as an inexpensive and effective biosorbent for the removal of heavy metals.

Dyes and Heavy Metals Removal from Aqueous Solutions Using Raw and Modified Diatomite

The progress of the textile industry has led to a severe increase in the discharge of colored effluents, polluted with dyes and metal ions (non-biodegradable, carcinogenic to humans and environmental hazards). The implementation of effective methodologies and materials for the treatment of wastewater has become an urgent requirement. The present work describes the application of two samples of mineral materials—Ghidirim diatomite and modified diatomite—as adsorbents for the removal of dyes—Acid Blue 350, Methylene Blue, Basic Red 2—and of metal ions—copper, zinc, and lead—from aqueous solutions. In order to determine the optimal working conditions by which to ensure maximum removal efficiency, the influence of the nature and amount of the sorbent, the initial concentration of pollutant, and the temperature were studied. Working under normal conditions (room temperature, solution pH) efficiencies greater than 80% were obtained for the removal of dyes and metal ions. The adsorption fitted well with the pseudo-second order kinetic model, and the maximum adsorption capacities were determined from the Langmuir isotherm model. The adsorption of investigated pollutants is an endothermic and spontaneous process. The results indicate that Ghidirim diatomite and modified diatomite have potential applications in water purification management, providing high removal efficiency of both dyes and metal ions.

Synergic binding of rhodamine-B and heavy metal ions onto polyethyleneimine grafted freeze-dried chitosan/epichlorohydrin composite beads and possible mechanism

This paper reports a synergic binding technique of dye and cadmium/lead ions onto freeze-dried modified chitosan beads (GCCS), in this work modified chitosan beads was applied in binary solution. Chitosan beads (CS) composite was produced and polyethyleneimine was grafted onto the backbone of the developed composite. The beads were analyzed utilizing different analytical techniques such as Fourier transform infrared (FTIR), thermogravimetric analysis (TGA), X-ray diffraction (XRD) and scanning electron microscope (SEM). The model applied in pH equilibrium was found to justify the adsorption of pollutants onto the adsorbent. The model was established from 2 equilibrium calculations, one justifying the acid-base attributes of the modified beads, the other elucidating the adsorption of the adsorbates onto the beads, and a mass balance of the various arrangement of nitrogen in the adsorbent. The excellent fit of the Pseudo-second order and intra-particle diffusion kinetic model shows that chemical binding might be the rate-limiting step. The adsorption isotherms were well represented by the Langmuir and Temkin models at a temperature of 45 °C. The maximum binding capacities (Qmax) from the Langmuir model were observed to be 390, 315 and 278 mg/g for the adsorption of dye, lead and cadmium ions respectively`. However, it was found to be higher in the binary system with the same applicable conditions. The correlation was analyzed utilizing various models and lines of best fit were obtained. Synergic effect was observed from the experimental results acquired from the adsorption of Rhodamine B (RHB) and adsorbates. These findings show the formation of fresh binding sites during simultaneous binding process.

Study on the mechanical strength and iodine adsorption behavior of coal-based activated carbon based on orthogonal experiments

To prepare coal-based activated carbon with high mechanical strength and adsorption performance for the removal of iodine from wastewater, the effects of carbonization temperature, heating rate, activation time and activator on the mechanical strength of activated carbon were studied; the optimal production conditions were determined by comprehensively considering the specific surface area, iodine value, compressive strength and wear resistance based on previous studies. Iodine adsorption kinetics and equilibrium adsorption experiments were carried out on activated carbon prepared under the optimum conditions. The results showed that the increase in mechanical strength was caused by the release of volatile matter and secondary reactions, which formed the carbon skeleton, while the decrease in mechanical strength was due to the intervention of the activator, which destroyed the carbon skeleton. The adsorption kinetics showed that a pseudo-second order kinetic model was more suitable for the adsorption behavior of iodine on activated carbon. The equilibrium adsorption experiment results showed that iodine was evenly adsorbed on the surface of activated carbon, and with increasing temperature, the affinity of the active sites of activated carbon to iodine also increased.

Efficient antibacterial and dye adsorption by novel fish scale silver biochar composite gel

A silver-loaded carbon-chitosan-polyvinyl alcohol gel (C/CTS/PVA) was designed for suppressing microbial growth and dye adsorption. The antibacterial test results showed that C/CTS/PVA gel had a good antibacterial ability against Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa. The inhibition rate in water was 100 %, and the antibacterial rate remained above 95 % within 35 days after preparation. The tight spatial structure provided by the adhesive effect of PVA and CTS effectively prevented water loss and enhanced the stability of the gel. The adsorption curves of the gel were fitted by establishing the pseudo-first order and pseudo-second order kinetic models. The adsorption curves were more consistent with the pseudo-second-order kinetic model. The best adsorption effect for Malachite green was 128.12 mg/g. C/CTS/PVA gel had a remarkable adsorption effect on Malachite green, Congo red, Methyl orange, and Methylene blue. In general, C/CTS/PVA gels have great potential for the treatment of sewage in the future.

Uptake of Fluoride from Water Using Recycled Raw Beef Bone as an Environmently Freindly Waste

Excessive intake of fluoride, mainly through drinking water is a serious health hazard affecting humans worldwide. In this study, the defluoridation capacities of locally available raw waste beef bones have been estimated. Several experimental parameters including contact time, pH, bone dose, fluoride initial concentration, bone grains size, agitation rate, and the effect of co-existence of anions in actual samples of wastewater were studied for fluoride removal from aqueous solutions. Results indicated excellent fluoride removal effeciency up to 99.7% at fluoride initial concentration of 10 mg F/L and 120 min contact time. Maximum fluoride uptake was obtained at neutral pH range 6-7. Fluoride removal kinetic was well described by the pseudo-second order kinetic model. Both, Langmuir and Freundlich isotherm models could fit the experimental data well with correlation coefficient values &gt; 0.99 suggesting favorable conditions of the process. Furthermore, it was found that the co-existing anions had no significant effect on fluoride removal. Ion exchange and fluoride precipitation are the modes of fluoride removal.

Preparation, characterization and adsorption potentiality of magnetic activated carbon from Eucalyptus sawdust for removal of amoxicillin: Adsorption behavior and mechanism

The magnetic activated carbon (MAC) from eucalyptus sawdust was prepared by one-step method and utilized to remove amoxicillin (AMX) from wastewater. MAC was characterized by N2 adsorption-desorption, XRD, FT-IRS, Raman, XPS, FESEM, SEM-EDS, vibrating sample magnetometer (VSM) and the point of zero charges (pHpzc). The magnetic parameters of MAC were found Hc of 55.92 Oe, Ms of 21.68 emu g1 and Mr of 0.63 emu g1, which resulted from existence of α-Fe and γ-Fe2O3. MAC existed micropores and mesopores, the specific surface area (SBET) and average pore width were 1263.7 m2 g1 and 2.07 nm, respectively. Batch adsorption experiments was designed to investigate AMX adsorption behavior on MAC, the adsorption mechanism was also investigated. The AMX removal efficiency was more than 94.3% when 50 mL 400 mg L1 AMX aqueous solution (3 of pH) was adsorbed by 0.055 g MAC for 6 h at 25 °C. The AMX adsorption process was consistent with Langmuir isotherm model and the pseudo-second order kinetic model, with maximum adsorption capacities of 485.4 mg g1 for AMX, the process was affected by the intraparticle diffusion, membrane diffusion and surface adsorption. The AMX adsorption on MAC was spontaneous nd endothermic. The adsorption of AMX on MAC was based on electrosttic interactions, π–π conjugation interactions, and hydrogen bond interactions. MAC had satisfactory adsorption capacity for AMX and recyclability. This work provides a green and environment-friendly method on antibiotic contamination wastewater treatment and a low-carbon green chemical technology for the high-value utilization of eucalyptus residues.

Cellulose nanofibers decorated with SiO2 nanoparticles: Green adsorbents for removal of cationic and anionic dyes; kinetics, isotherms, and thermodynamic studies

Cellulose nanofibers decorated with SiO2 nanoparticles (SiO2-CNF) were prepared by the extraction of cellulose nanofibers from Yucca leaves, followed by modification with SiO2 nanoparticles, and used as efficient materials for the removal of both anionic and cationic dyes from the aqueous solution. Prepared nanostructures were characterized using Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction powder (XRD), Thermogravimetric analysis (TGA), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), and transmission electron microscopy (TEM) analysis. The adsorption capacity of the nanostructures was investigated for the removal of both cationic (Methylene Blue, MB, and Crystal Violet, CV) and anionic (Eriochrome Black-T, EB) dyes. The kinetics of adsorption were investigated using some well-known models, including intraparticular diffusion (IPD), pseudo-first-order (PFO), pseudo-second-order (PSO), and Elovich. The adsorption isotherms were also explored using the Langmuir, Freundlich, Temkin, and Redlich-Peterson models. The obtained results revealed that the adsorption processes follow PSO kinetic and Langmuir isotherm models. Thermodynamic parameters of the adsorption were measured at different temperatures, indicating the feasibility and spontaneity of the adsorption. The pH and salt effects on adsorption were also explored. Finally, according to the reusability tests, the prepared adsorbents showed high recoverability without considerable loss in adsorption efficiency after five repeated runs.

Adsorption of Pb2+ and Cd2+ in Agricultural Water by Potassium Permanganate and Nitric Acid-Modified Coconut Shell Biochar

Biochar prepared from agricultural waste resource coconut shells was used as the original charcoal, which was oxidatively modified and characterized using batch adsorption tests before and after modification by SEM, FTIR, surface area, and elemental analyses. The removal capacity and adsorption mechanism of the modified biochar for Pb2+ and Cd2+ in water were investigated, and its adsorption kinetics and thermodynamics were discussed. The findings demonstrated that the specific surface area of potassium permanganate and nitric acid-modified coconut shell carbon (MHBC) is 3.02 times than that of the coconut shell carbon (BC). The kinetic data of adsorption of Pb2+ and Cd2+ on MHBC were more in accordance with the pseudo-second order kinetic model, indicating that chemical adsorption played a dominant role, and the adsorption rate gradually tended to balance with a decrease in solution ion concentration. The isothermal thermodynamic data of the adsorption of Pb2+ and Cd2+ by MHBC conformed to the Langmuir model. At pH = 5.5, the maximum adsorption capacities of Pb2+ and Cd2+ were 160.41 mg·g−1 and 47.46 mg·g−1, respectively. Thermodynamic parameter fitting showed that the process of adsorption of Pb2+ and Cd2+ by MHBC is a spontaneous endothermic reaction. The higher the temperature is, the stronger the adsorption capacity is. When the ions coexist, Pb2+ and Cd2+ have obvious competitive adsorption, and Pb2+ has a significant competitive advantage. Among them, MHBC has high adsorption and good reusability for Pb2+ and Cd2+, and has good practical application prospects.