Boyd Model Research Articles

KOH-activated tire pyrolysis char as an adsorbent for chloroorganic water pollutants

Activated carbons (ACs) produced from end-of-life tires with different tire pyrolysis char (TPC)-to-activator (KOH) ratios of 1:2, 1:3, and 1:4 were prepared and characterized. These materials were used as adsorbents for the removal of two common chloroorganic water contaminants such as 2,4-dichlorophenol (DCP) and 2,4-dichlorophenoxyacetic acid (2,4-D). The adsorption kinetics, equilibrium adsorption, and effects of solution pH were investigated. The adsorption of both adsorbates was found to be pH-dependent and preferred in acidic environments. The adsorption kinetics was evaluated using pseudo-first-order and pseudo-second-order kinetic models and mechanism - using Weber-Morris and Boyd models. Results demonstrated that the adsorption of DCP and 2,4-D on all ACs followed the pseudo-second-order model and was controlled by film diffusion. The Langmuir isotherm described the equilibrium data better than the Freundlich isotherm model. The maximum adsorption capacity of DCP adsorbed on AC1:2, AC1:3, and AC1:4 at equilibrium was 0.582, 0.609, and 0.739 mmol/g, respectively, while the maximum adsorption capacities for 2,4-D were 0.733, 0.937, and 1.035 mmol/g, respectively. The adsorption rate and efficiency were closely correlated with the porous structure of the tested adsorbents. The results showed that the activated carbons obtained from the scrap of end-of-life tires as raw materials could be used as a low-cost and alternative adsorbent for the removal of chlorinated organic pollutants from water.

Modeling of adsorptive treatment of lead (II) ions contaminated effluents using cashew nut shell alkali activated carbon: Batch kinetic, isothermal and thermodynamic studies

The numerical study of the decontamination of lead(II) ions-rich effluent employing activated carbon derived from cashew nut shell was the central focus of this work. Chemical activation with zinc chloride (ZnCl2) was used to produce powdered activated carbon at optimized activation conditions of impregnation ratio (0.531), activation temperature (1083 K) and activation time (63min). The physiochemical properties of raw and activated cashew nut shell were determined using Fourier transform infrared spectroscopy, scanning, X-ray diffractor (XRD), scanning electron microscopy (SEM), and Brunauer-Emmet-Teller (BET) analyses. Batch adsorption experiments were performed at varied process conditions of temperature (303–323) K, contact time (5–80min), and initial lead(II) ion concentrations (100–400 mg.L−1). The adsorption behavior of the batch–type operation was mathematically described in the form of non-linear parabolic partial differential equations (PDE’S) incorporating film, pore and surface diffusion mechanisms. The batch mathematical model was solved by implementing a custom MATLAB program-OkiyNwabannebatch and calibrated to predict the desired response (percentage removal) using measured adsorption data. The equilibrium adsorption, kinetics and thermodynamics of lead(II) ions adsorption onto activated cashew nut shell were also assessed using nonlinear isotherm, kinetic and thermodynamic models. Sensitivity analysis unveiled that temperature with sensitivity value of 37.31 % had a predominant effect on the model performance. The simulated equilibrium data was well explicated by the Freundlich model for lead(II) ions adsorption onto activated cashew nut shell. The pseudo-second order kinetic model best reproduced the simulated adsorption data for lead(II) ions uptake by cashew nut shell adsorbent. Likewise, the kinetic data followed Boyd model, indicating that the adsorption process is controlled by external (film) diffusion for the uptake of lead(II) ions by alkali activated cashew nut shell. Thermodynamic analysis using the Gibbs and Van’t Hoff’s models indicated that lead(II) ions adsorption by modified cashew nut shell is spontaneous and exothermic. The physical nature of the adsorption process was elucidated from the low values of the isosteric heats of adsorption (ΔHX) evaluated (<80 kJ mol−1). This study showed that zinc chloride activated cashew nut shell has good potential to be used as a cost-effective and efficient adsorbent for the uptake of lead(II) ions from aqueous solution.

Enhanced Hydrophobicity and Oleophilicity of Modified Activated Carbons Derived from Agro-Wastes Biomass for the Removal of Crude Oil from Aqueous Medium

Crude oil spillage has tremendous environmental impacts and poses severe pollution problems worldwide due to the continuous activities and operations in the oil and gas sector. This has resulted in the urgent need for clean-up techniques such as the use of natural adsorbents which is considered a relatively low-cost, readily-available, efficient, eco-friendly, and easy-to-deploy mode of addressing oil spillage due to its high oil sorption capacity/efficiency, high oil selectivity, oleophilic, enduring, reusability and biodegradable properties. Empty palm fruit bunch and coconut coir were used as precursors to produce activated carbons for oil spill remediation. The influence of varying parameters was investigated using a batch experimental procedure resulting in the crude oil adsorption capacity increasing with a corresponding increase in contact time, initial oil concentration, temperature, agitation speed, and particle size but decreasing in adsorbent dosage. The combination of surface morphological modification and hydrophobicity enhancement resulted in significantly improved adsorption capacity for crude oil removal (2710.0 mg/g and 4859.5 mg/g for EPFBAC&amp;lt;SUB&amp;gt;LA&amp;lt;/SUB&amp;gt; and CCAC&amp;lt;SUB&amp;gt;L.A&amp;lt;/SUB&amp;gt; respectively), as evidenced by both FTIR and SEM analyses. The experimental isotherm data were analysed using various isotherm models and the best-fitted isotherm model was the Freundlich model with a correlation coefficient (R&amp;lt;sup&amp;gt;2 &amp;lt;/sup&amp;gt;= 0.991 and R&amp;lt;sup&amp;gt;2 &amp;lt;/sup&amp;gt;= 0.999) for EPFB&amp;lt;SUB&amp;gt;L.A&amp;lt;/SUB&amp;gt; and CCAC&amp;lt;SUB&amp;gt;L.A&amp;lt;/SUB&amp;gt; respectively. The kinetic behaviour of the adsorption process was best described by pseudo-second order with R&amp;lt;sup&amp;gt;2&amp;lt;/sup&amp;gt; values of 0.970 and 0.999 for EPFBAC&amp;lt;SUB&amp;gt;LA&amp;lt;/SUB&amp;gt; and CCAC&amp;lt;SUB&amp;gt;L.A&amp;lt;/SUB&amp;gt; respectively while Boyd model revealed that the adsorption was controlled by an internal transport mechanism and film diffusion was the rate-limiting step. The crude oil adsorption was chemisorption and endothermic owing to the positive enthalpy values (ΔH&amp;lt;sup&amp;gt;o&amp;lt;/sup&amp;gt; = 183.890 KJ/mol for EPFBAC&amp;lt;SUB&amp;gt;L.A &amp;lt;/SUB&amp;gt;and ΔH&amp;lt;sup&amp;gt;o&amp;lt;/sup&amp;gt; = 69.656 KJ/mol for CCAC&amp;lt;SUB&amp;gt;L.A&amp;lt;/SUB&amp;gt;), the positive value of entropy suggested that the adsorption process was accompanied by an increase in the degree of randomness or disorder at the interface between the adsorbent and the adsorbate. A temperature rise led to a decline in Gibbs energy (ΔG&amp;lt;sup&amp;gt;o&amp;lt;/sup&amp;gt;), suggesting that adsorption became more feasible and spontaneous at higher temperatures and the significant activation energies indicated the existence of a substantial energy barrier that must be overcome to initiate the reaction. The results showed the significant capability of the prepared adsorbents to be used as a low-cost, re-generable and eco-friendly adsorbent in oil spill clean-up and is recommended to exploit its usage on a large scale.

Removal of per- and polyfluoroalkyl substances (PFAS) from water using magnetic cetyltrimethylammonium bromide (CTAB)-modified pine bark

Per- and polyfluoroalkyl substances (PFAS) have gained global attention in recent years due to their adverse effect on environment and human health. In this study, a novel and cost-effective sorbent was developed utilizing forestry by-product pine bark and tested for the removal of PFAS compounds from both synthetic solutions and contaminated groundwater. The synthesis of the adsorbent included two steps: 1) loading of cetyltrimethylammonium bromide (CTAB) onto the pine bark and followed by 2) a simple coating of magnetite nanoparticles. The developed sorbent (MC-PB) exhibited 100 % perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) removal from synthetic solution (10 µg/L PFOA and PFOS) and enabled quick magnetic separation. A rapid removal of PFOA (> 80 %) by MC-PB was observed within 10 min from synthetic PFOA solution and the adsorption equilibrium was reached within 4 h, achieving > 90 % removal of PFOA (dosage 2 g/L, PFOA 10 mg/L, initial pH 4.2). The PFOA adsorption kinetics fitted well to an optimized pseudo-order model (R2=0.929). Intra-particle diffusion and Boyd models suggested that the adsorption process was not governed by pore diffusion. The maximum PFOA adsorption capacity was found to be 69 mg/g and the adsorption isotherm was best described by the Dual Mode Model (R2=0.950). The MC-PB demonstrated > 90 % PFOA and PFOS removal from contaminated groundwater. Furthermore, both short- and long-chain perfluorosulfonic acids and 6:2 fluorotelomer sulfonate were efficiently removed resulting in 83.9 % removal towards total PFAS (2 g/L dosage).

Evaluation of reduced graphene oxide from cotton waste as an efficient phenol adsorbent in aqueous media.

The elimination of organic substances, such as phenol, in conventional and biological processes, has been considered a challenge for the petroleum industry. In this work, reduced graphene oxide (rGO), obtained from cellulosic biomass (CB-rGO), as cotton waste, was employed as a phenol adsorbent in an aqueous solution simulating refinery effluent. The CB-rGO was characterized using HRTEM, Raman, XRD, FTIR, BET, and zeta analysis. The behavior of variables such as pH, contact time, temperature, CB-rGO mass, and adsorbate concentration on the characteristics of the adsorption process were continuously investigated. These parameters of the adsorption process were evaluated across a range of adsorbent concentrations from 100 to 300mg/L, pH in the range of 2-11, adsorbent mass 5-25mg, contact time of 0-180min, and temperature of 20-60°C. The adsorption isotherm data were better described by the Freundlich equation compared to the Langmuir and Sips models, despite the small difference in R2 values. Mechanism diffusion was analyzed using the Boyd model and confirmed to be the rate-limiting step in the adsorption process. The endothermic nature of this CB-rGO adsorption process with phenol was confirmed by verifying the thermodynamic data. This successful removal of phenol from synthetic effluents highlights the promising potential of this adsorbent obtained from an industrial residue and being an ecologically more sustainable alternative compared to the synthesis of other materials identified to remove this contaminant.

Study on the adsorption performance of zeolite imidazole frameworks materials for Co(II) and Mn(II) in solution

Abstract The radionuclides 60Co and 54Mn are the main activation products produced in the operation of nuclear power facilities. Wastewater with these radionuclides must be treated to meet standards before being discharged. A variety of zeolite imidazole frameworks (ZIFs) materials were synthesized at room temperature, and the adsorption effect of ZIF-67 was found to be the best through adsorption experiments on Co(II) and Mn(II). The thermal stability test and structural characterization of ZIF-67 were carried out. At the same time, the influence of the initial pH value, adsorption time, and initial concentration of the solution on the adsorption of Co(II) and Mn(II) by ZIF-67 was investigated. The results show that: ZIF-67 has a microporous structure with a BET surface area of 1,035.72 m2/g. In addition, ZIF-67 has good thermal stability, under the condition of pH = 6, a temperature of 303 K and the initial concentration of 500 mg/L. The saturated adsorption capacity for Co(II) and Mn(II) reached 230.25 mg/g and 338.75 mg/g, respectively. ZIF-67 exhibits good selective adsorption performance for Co(II) and Mn (II) in high concentration interfering ion solutions and multi-ion solutions. The adsorption process of ZIF-67 was analyzed by kinetics, thermodynamics, isotherms, and adsorption diffusion models. The analysis of thermodynamic parameters shows that the adsorption process of ZIF-67 to Co(II) and Mn(II) is spontaneous and endothermic. The pseudo-second-order kinetic model, Langmuir isotherm model, and Boyd model are more in line with the adsorption process of Co(II) and Mn(II) by ZIF-67. It shows that the active sites on the surface of ZIF-67 are evenly distributed, and the adsorption process is single-molecule chemical layer adsorption. In addition, the liquid film diffusion dominates the adsorption rate during the adsorption process of Co(II) and Mn(II) by ZIF-67.

Experimental study of methylene blue adsorption from aqueous solutions onto natural Algerian goethite

ABSTRACT The objective of this work is to study and model the methylene blue (MB) sorption, from aqueous solutions by goethite. The equilibrium time was reached during 10 min of agitation with 26.21 ℅ efficiency. MB removal efficiency is improved with an increased absorbent dose (0.5–08 g/L) for an initial 10 mg/L concentration. Treatment efficiency decreases with the increase of initial MB concentration (2–100 mg/L). The best adsorption yields were obtained in basic media. MB sorption kinetics via goethite leads to several results as to mechanisms that govern kinetics and isotherms equilibrium: Blanchard's model provides a better fit of the experimental results compared to Lagergren's model. Thus, the MB sorption kinetics is described by the pseudo-second order. Particle diffusion is involved in the MB removal mechanism, but it is not the only limiting step and the Boyd model application confirms that diffusion in the pores is the limiting step of the MB sorption process. The Elovich model is well verified and translated probably the existence of chemical-type interactions between MB and goethite. The study of MB adsorption isotherms showed that Freundlich, Temkin, and Elovich models are the best adapted than the Langmuir model. Finally, we can assess that goethite can be an interesting natural adsorbent for MB elimination from polluted waters in basic environments.

Boyd’s film diffusion model for water contaminant adsorption: Time for an upgrade?

The Boyd film diffusion model is widely used in liquid phase adsorption studies for its mathematical simplicity and straightforward data analysis. However, a lack of awareness regarding its restrictive assumptions has led to widespread misuse. The Boyd model assumes film diffusion as the rate-controlling mechanism and rests on two additional pivotal assumptions: adsorption occurs under infinite bath conditions and follows a linear equilibrium relationship. This study examines the recurrent breaches of these assumptions across a growing body of research on water contaminant adsorption. Nearly all kinetic data have been derived from finite bath experiments governed by nonlinear isotherms, which directly contradict the Boyd model’s assumptions. Consequently, applying the Boyd model to such data can yield misleading results and interpretations. To address these challenges, alternative models tailored for finite bath conditions and capable of accommodating both linear and nonlinear isotherms should be considered. These models offer more accurate insights into adsorption kinetics under realistic experimental settings. While the Boyd model remains valuable under specific conditions, its stringent assumptions restrict its broader applicability. Researchers should critically assess the validity of these assumptions and explore alternative models when analyzing liquid phase adsorption kinetics to ensure robust and reliable results.

Novel amino-ethyl carboxymethyl cellulose crosslinked ampholyte hydrogel development for Methyl orange removal from waste water

In the modern era, with the rapid growth of various industries, the issues of energy crisis and environmental pollution have garnered increasing attention. One significant source of industrial pollution is printing and dyeing wastewater. This wastewater often contains dyes that have aromatic structures and azo groups, such as Methyl orange (MO), which are both toxic and difficult to degrade. If these dyes are released into the wastewater stream without any treatment, they can have adverse effects on ecological balance and human health. Therefore, it is crucial to identify suitable treatment strategies to efficiently remove dyes from wastewater systems before discharge. In this study, the Methyl orange (MO) azo dye has been removed from dyes-contaminated wastewater, for the first time, using a novel amino-ethyl carboxymethyl cellulose crosslinked ampholyte hydrogel (AECMC). Different characterization methods, including FTIR, TGA, and DSC were used to characterize the generated AECMC compounds. The water absorption and cationic exchange capacities were assessed. Factors affecting the MO anions adsorption including MO concentration, adsorption pH, temperature, time, adsorbent dose, and agitation speed have been investigated. Moreover, the kinetics of the adsorption process was assessed by the use of three models: pseudo-first-order, Pseudo-second-order, and Elovich. Moreover, the mechanism of the adsorption process was monitored using the Intraparticle diffusion and Boyd models. Additionally, the adsorption isotherm was examined using established models such as Langmuir, Freundlich, and Temkin isotherms. The thermodynamic characteristics of the MO adsorption process have been investigated at various adsorption temperatures using the Van't Hoff model. The results obtained from the study indicate that the process of MO adsorption adhered to the Pseudo-second-order kinetic model, the Langmuir isotherm model was found to be applicable, and spontaneous and exhibited an endothermic character. In conclusion, the developed novel amino-ethyl carboxymethyl cellulose crosslinked ampholyte hydrogels (AECMC) have successive in the removal of the MO anionic dye from contaminated wastewater.

Removal of Bisphenol S (BPS) by Adsorption on Activated Carbons Commercialized in Brazil.

This study assessed three powdered activated carbons (BETM, COCO, and SIAL) commercialized in Brazil at the bench scale in agitated reactors, analyzing their kinetic behavior and adsorptive capacity for BPS and BPA in ultrapure water. BETM exhibited the highest adsorption capacities (Q0max) for BPS and BPA at 260.62 and 264.64 mg/g, respectively, followed by SIAL, with a Q0max of 248.25 mg/g for BPS and for 231.20 mg/g BPA, and COCO, with a Q0max of 136.51 mg/g for BPS and 150.03 mg/g for BPA. The Langmuir isotherm model can describe the processes well. A pseudo-second-order model can describe the adsorption kinetics, and SIAL carbon had the highest rate constants (7.45 × 10-3 mg/g/min for BPS and 2.84 × 10-3 mg/g/min for BPA). The Weber-Morris intraparticle diffusion model suggests intraparticle diffusion as the rate-limiting step of all adsorption processes. Boyd's model confirmed more than the mechanism actuating in the bisphenol adsorption. The results suggest that adsorbents with basic surfaces, high specific surface areas, and high mesopore volumes tend to remove BPS and BPA efficiently. Therefore, activated carbons can effectively complement the existing treatment in Brazilian water treatment plants (WTPs).

Viability and life cycle assessment of Fuller's Earth as a low-cost adsorbent for zinc removal from aqueous solutions: Operating parameters, removal mechanisms and environmental impacts

Zinc is a heavy metal that has several health risks and must be removed from wastewater effluents before discharge to water bodies or reuse. Fuller's earth is a sedimentary clay and characterized by its low cost and availability. In this research, Fuller's earth (FE) was investigated as an adsorbent for the Zinc (Zn) removal from aqueous solutions to understand its performance, the mechanism of removal, and the potential environmental impacts. Life cycle assessment (LCA) was conducted using ReCiPe 2016 midpoint method. Zn adsorption studies on FE were conducted at various pH (2.5–9), temperatures (10°C, 25°C, and 40°C), initial concentrations of Zn (25, - 150 mg/L) and adsorbent doses of (0.25–4 g/ 50 ml). The Zn removal efficiency reached 99% at pH = 9 at an initial Zn concentration = 100 mg/L and the adsorbent dose = 0.25 g/ 50 ml. The experimental data fit into the Temkin isotherm, while kinetics were best expressed by pseudo-second order. The controlling step of the adsorption process was the film diffusion according to Boyd model. Thermodynamic experiments showed that adsorption is endothermic with an accompanying rise in randomness in the system. The adsorption capacity was 3.56 mg/g. Images by SEM confirmed the occurrence of adsorption. The desorption was successful at different concentrations of HCl. LCA results showed that the maximum negative and positive environmental impacts were associated with mineral resource scarcity (7.5*10–5 kg Cu eq) and human non-carcinogenic toxicity (−0.821 kg 1,4-DCB), respectively.

Quaternary branched polyethylenimine‐based nanocomposite for removal of NO3− ions from aqueous solutions

AbstractThis study synthesized a nanocomposite based on quaternary branched polyethyleneimine containing sodium alginate and graphene oxide and characterized by FE‐SEM, EDX‐MAP, XRD, FT‐IR, and TGA and used as an efficient sorbent for the removal of nitrate ions. The maximum ion exchange in optimized conditions was discovered to be 75%. The experimental studies showed that nitrate removal follows the pseudo‐first‐order model due to more consonance. Also, Weber–Morris and Boyd models suggested that the nitrate ions adsorption on the surface of nanocomposite is not controlled only by the intraparticle diffusion step. Moreover, Langmuir, Redlich–Peterson, and Hill models exhibited high regression coefficients of 0.991, 0.993, and 0.992, respectively. Thermodynamic studies confirmed the adsorption system was spontaneous and exothermic. Recovery assay showed that more than 98% of the nitrate ion exchanged by the nanocomposite was regenerated and nanocomposite could be reused seven cycles without efficacy reducing significantly. The nanocomposite showed excellent antibacterial activity against Staphylococcus aureus and Escherichia coli cells, with minimum inhibitory concentrations of 62.5 and 125 μg mL−1, and zone of growth inhibition of 17.5 ± 0.5 and 10.5 ± 0.5 mm, respectively. The results represented that the introduced nanocomposite is a useful material for the removal of nitrate ions from aqueous solution and has antibacterial properties.

Nanozinc ferrites @ silica as efficient adsorbent for dye removal from wastewater: synthesis and adsorption studies

The precipitation process was successfully employed to prepare ZnFe2O4 and ZnFe2O4@SiO2 nanoparticles. The synthesized nanoadsorbents were characterized employing transmission electron microscopy (TEM), X-ray diffraction (XRD), and Brauner-Emmett and Teller (BET) methods. The potential adsorption capacities of the generated nanoparticles were assessed under various conditions, including pH, starting dye concentration, contact time, and temperature. The adsorption efficiency of ZnFe2O4@SiO2 nanoparticles (95%) was higher than ZnFe2O4 (93%). The adsorption data were described using Langmuir, Freundlich, Temkin, and Dubinin-Kaganer-Radushkevich (DKR) isotherm models. The methylene blue (MB) removal kinetics by ZnFe2O4 and ZnFe2O4@Silica nanoparticles were evaluated using linear pseudo-first-order (PFO) and pseudo-second-order (PSO) models. The removal fitted to pseudo-second-order (PSO) models as the correlation coefficient (R2) value was (0.9994). The Boyd model may be used to validate the kinetics data, and it can be deduced that the rate-determining phase was not intra-particle diffusion, but rather the hypothesized adsorption process was endothermic and spontaneous in nature. Based on the findings, ZnFe2O4@silica is an adsorbent material that may be useful in removing methylene blue from aqueous solutions.

Effects of Particle Size on the Gas Uptake Kinetics and Physical Properties of Type III Porous Liquids.

Type III porous liquids (PLs) consist of porous solid particles dispersed in a size-excluded liquid phase and are attracting much attention as novel media for applications such as gas separation. However, the effects of fundamental variables such as particle size on their physical properties are currently largely unknown. Here we study the effects of particle size in a series of porous liquids based on solid Al(OH)(fumarate) (a microporous metal-organic framework, MOF) with particle sizes of 60 nm, 200-600 nm, or 800-1000 dispersed in liquid polydimethylsiloxane (PDMS). Properties examined include physical stability of the dispersion, viscosity, total CO2 uptake, and kinetics of CO2 uptake. As expected, both physical stability and viscosity decreased with increasing particle size. Unexpectedly, total gravimetric gas uptake also varied with particle size, being greatest for the largest particles, which we ascribe to larger particles having a lower relative content of surface-bound FMA ligands. Various models for the gas uptake kinetic data were considered, specifically adsorption reaction models such as pseudo-first-order, pseudo-second-order, and Elovich models. In contrast to pure PDMS, which showed first-order kinetics, all PLs fit best to the Elovich model confirming that their uptake mechanism is more complex than for a simple liquid. Adsorption diffusion models, specifically Weber and Morris' intraparticle model and Boyd's model, were also applied which revealed a three-step process in which a combination of diffusion through a surface layer and intraparticle diffusion were rate-limiting. The rate of gas uptake follows the order PDMS < PL1 < PL2 < PL3, showing that the porous liquids take up gas more rapidly than does PDMS and that this rate increases with particle size. Overall, the study suggests that for high gas uptake and fast uptake kinetics, large particles may be preferred. Also, the fact that large particles resulted in low viscosity may be advantageous in reducing the pumping energy needed in flow separation systems. Therefore, the work suggests that finding ways to stabilize PLs with large particles against phase separation could be advantageous for optimizing the properties of PLs toward applications.

Microalgae derived honeycomb structured mesoporous diatom biosilica for adsorption of malachite green: Process optimization and modeling

The present study investigated the removal of malachite green dye from aquifers by means of microalgae-derived mesoporous diatom biosilica. The various process variables (dye concentration, pH, and adsorbent dose) influencing the removal of the dye were optimized and their interactive effects on the removal efficiency were explored by response surface methodology. The pH of the solution (pH = 5.26) was found to be the most dominating among other tested variables. The Langmuir isotherm (R2 = 0.995) best fitted the equilibrium adsorption data with an adsorption capacity of 40.7 mg/g at 323 K and pseudo-second-order model (R2 = 0.983) best elucidated the rate of dye removal (10.6 mg/g). The underlying mechanism of adsorption was investigated by Weber-Morris and Boyd models and results revealed that the film diffusion governed the overall adsorption process. The theoretical investigations on the dye structure using DFT-based chemical reactivity descriptors indicated that malachite green cations are electrophilic, reactive and possess the ability to accept electrons, and are strongly adsorbed on the surface of diatom biosilica. Also, the Fukui function analysis proposed the favorable adsorption sites available on the adsorbent surface.

Giant mud crab shell biochar: A promising adsorbent for methyl violet removal in wastewater treatment

Giant mud crab (Scylla serrata sp.) shell prepared through pyrolysis at various temperatures without any modification were characterized for physicochemical properties and methyl violet (MV) removal potential. Hence, this paper investigated the performance and mechanism of biochar derived from giant mud crab shell as adsorbent in the removal of methyl violet as well as the potential for regenerating adsorbents via hot water regeneration. The results show that CSB500 (produced through pyrolysis at 500 °C) exhibits a surface area of 59.73 m2/g and mesopore size of 31.3 nm, favorable for methyl violet removal at 3139 mg/g. The equilibrium adsorption data agreed well with Langmuir and Redlich-Peterson isotherm models, indicating a monolayer adsorption of MV. The kinetics data fitted better with both pseudo-first-order and pseudo-second-order models. The intraparticle diffusion and Boyd's models revealed that both film and pore diffusion may be involved in the adsorption process. In hot water regeneration studies, CSB500 shown superior regeneration performance when using water with temperature of 70 °C rather than 30 °C for 9th regeneration cycles, with retained to achieve >90 % MV removal for 6th regeneration cycles. Biochar derived from giant mud crab shell has shown significant promise as a low-cost, effective, and ecologically friendly with reasonably good adsorption capacity and reusability for dye removal, and it can be considered as an environmental sustainability strategy in wastewater treatment.

The Adsorption Studies for the Removal of Lead (Pb2+) from Paint Industrial Wastewater using Avocado Seed Activated Carbon (ASAC)

The rapid increase in industrial activities in Nigeria has led to the high contamination of water bodies with heavy metals such as Lead, Cadmium, Zinc etc from wastewater disposal. Previous techniques adopted for this wastewater treatment such as ion exchange, biosorption, solvent extraction and precipitation etc are highly expensive and capital intensive; hence, the need for cheaper technologies that utilizes locally available biomass as a precursor for the preparation of activated carbon. This study aims to utilize avocado seed for the production of activated carbon to treat paint industrial wastewater containing heavy metals such as Lead (Pb2+) and to evaluate the adsorption isotherm and kinetic models that best fit the equilibrium data obtained from the batch adsorption experiment. The avocado seed activated carbon (ASAC) was prepared by carbonizing the sample at a temperature of 700 °C and activating it with a 30 % v/v Concentration of H3PO4 acid at a temperature of 500 °C for 6 hours in a muffle furnace. The batch adsorption studies were done by investigating the varying effect of metal ion concentration (0.5-3.0 mg/L), contact time (15-180 mins) and adsorbent dosage (0.5-3.0 g). The data obtained were analysed using six adsorption isotherms such as Langmuir, Freundlich, Temkin, Toth, Sips and Redlich-Peterson methods. Freundlich isotherm model with an R2 value of 0.94 and adsorption capacity of 0.1965 mg/g showed the highest percentage removal of Lead (Pb2+) to be &gt; 97 %. The kinetic studies revealed that the experimental data fitted well to the pseudo-first-order model with a high correlation coefficient of 0.980 when compared to other models like pseudo-second-order, intra-particle diffusion and Boyd model, thus; signifying that the adsorption’s mechanism was physiosorption. Thus, optimum activation conditions would produce higher activated carbon from avocado seeds that could be used for the removal of heavy metal ions from industrial wastewater, which will aid in eliminating the challenge of agricultural waste accumulation in the environment.

Novel amino-ethyl carboxymethyl cellulose crosslinked ampholyte hydrogel development for Methyl Orange Removal from Waste water: Kinetics, isotherms, and thermodynamics studies

In this study, a novel ampholyte hydrogel known as amino-ethyl carboxymethyl cellulose crosslinked hydrogel (AECMC) was synthesized and utilized to remove Methyl orange (MO), an azo-dye commonly found in dyes contaminated wastewater. This marks the first instance of such a hydrogel being generated for this specific application. The presence of induced amine groups in the modified carboxymethyl cellulose matrix facilitated the creation of adsorption positive charge centers, which effectively attracted MO azo-dye anions. The level of amination exhibits a clear correlation with both the percentage of MO adsorption and the capabilities of adsorbents. An initial rapid adsorption phenomenon was seen within the first 15 min, followed by a gradual decrease in the rate of adsorption until reaching a plateau. The adsorption capacity is notably influenced by the temperature of adsorption, particularly in the case of employing low aminated carboxymethyl cellulose (CMC) derivative. The aforementioned effect exhibits a decrease in magnitude when increasing levels of aminated carboxymethyl cellulose (CMC) derivatives are employed. The kinetics of the adsorption process was assessed by the use of three models: Pseudo-first-order, Pseudo-second-order, and Elovich. Moreover, the mechanism of the adsorption process was monitored using two models, namely Dumwald–Wagner and intraparticle models, which described the liquid film diffusion or intraparticle diffusion, while the external mass transfer was examined by the Boyd model. The Boyd diffusion model determines that the process rate is limited by film diffusion. Additionally, the adsorption isotherm was examined using established models such as Langmuir, Freundlich, and Temkin isotherms. The thermodynamic characteristics of the MO adsorption process have been investigated at various adsorption temperatures using the Van't Hoff model. The results obtained from the study indicate that the process of MO adsorption adhered to the Pseudo-second-order kinetic model. Additionally, the Langmuir isotherm model was found to be applicable, with a maximum adsorption capacity of 2.033 mg/g for the Langmuir monolayer. Furthermore, it was observed that the adsorption process was spontaneous and exhibited an endothermic character.

Coal gangue geopolymers as sustainable and cost-effective adsorbents for efficient removal of Cu (II)

Coal gangue geopolymers (GP) were employed to eliminate Cu (II) as an economical absorber. This study explores the feasibility of employing coal gangue geopolymers (GP) to be an economical absorber with a function of eliminating Cu (II). The results showed that GP is a mesoporous structure, which pore size distribution is around 5.60 nm. The optimal adsorption capacity of Cu (II) was achieved when the ratio n(SiO2)/n(Na2O) was 1.2. Cu (II) adsorption capacity of GP may achieve a maximum of 72.3 mg/g. Silicon and aluminum hydroxide groups of GP facilitated strong interactions and effective trapping of Cu (II). Data analysis discovered that the adsorption procedure in examinations followed a pseudo-second-order kinetic model, with the Langmuir model providing the best appropriate to the adsorption isotherm data. These confirm that charge and chemisorption simultaneously appeared in the spontaneous Cu (II) adsorption on GP. The intra-particle diffusion model (IPD) and Boyd models supported by observation that positive relationships result in initial Cu (II) adsorption onto the outer layer of GP, followed by subsequent diffusion into internal pores. Internal and external diffusion processes jointly dominate the Cu (II) adsorption rate. Furthermore, the adsorption-related characteristics of a combination of Cu (II) and Cr (VI) demonstrated that GP effectively removes Cr (VI) without compromising its adsorption performance for Cu (II), without any discernible competition or synergy between the two. Notably, the GP could be reused for five times, and Cu (II) removal rate is 80.88%, indicating the possibility of its application as an effective, sustainable Cu (II) removal absorbent.

Post-buckling and vibration analysis of double-curved sandwich panels with SMA embedded faces

Shape memory alloys, especially in the form of wire, can provide structures with magnificent improvements in buckling and frequency responses. The SMA's ability to recover its original shape can produce a sizable amount of recovery stress, resulting in enhancing natural frequency and critical temperature and lowering the maximum deflection of structures. In this study, in addition to considering the effects of SMA presence in double-curved sandwich plate on the aforementioned characteristics, the influences of heat treatment of curing SMAs on their properties, calculated by differential scanning calorimetry (DSC) and tensile testing, and sandwich structures will be considered. Furthermore, the effects of recovery stress, the volume fraction, and the position of SMA wires on thermal and mechanical stability will be studied. The Boyd & Lagoudas SMA constitutive model is utilized in the ABAQUS UMAT subroutine.