Harkins-Jura Isotherm Models Research Articles

Impact of Pyrolysis Temperature on the Physical and Chemical Properties of Non-Modified Biochar Produced from Banana Leaves: A Case Study on Ammonium Ion Adsorption.

Given the current importance of using biochar for water treatment, it is important to study the physical-chemical properties to predict the behavior of the biochar adsorbent in contact with adsorbates. In the present research, the physical and chemical characteristics of three types of biochar derived from banana leaves were investigated, which is a poorly studied raw material and is considered an agricultural waste in some Latin American, Asian, and African countries. The characterization of non-modified biochar samples pyrolyzed at 300, 400, and 500 °C was carried out through pH, scanning electron microscopy, energy dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, and specific surface area measurements. The adsorption properties of banana leaf-derived biochar were evaluated by ammonium ion adsorption experiments. The results demonstrated that the pyrolysis temperature has a large impact on the yield, structure, elemental composition, and surface chemistry of the biochar. Biochar prepared at 300 °C is the most efficient for NH4+ adsorption, achieving a capacity of 7.0 mg of adsorbed NH4+ on each gram of biochar used, while biochar samples prepared at 400 and 500 °C show lower values of 6.1 and 5.6 mg/g, respectively. The Harkins-Jura isotherm model fits the experimental data best for all biochar samples, demonstrating that multilayer adsorption occurs on our biochar.

Ultrahigh and kinetic-favorable adsorption for recycling urea using corncob-derived porous biochar

Insufficient attention has been given to the recycling of excess urea despite its potential detrimental effects on soil nutrient equilibrium, geological structure, and crop health. In this study, corncob-derived porous biochar (CPB), which is rich in surface functional groups, was prepared from biomass corncob in two steps as an adsorbent to remove urea from wastewater. Compared with the typical carbonization and activation processes, this process resulted in a higher yield of CPB and an ultrahigh adsorption capacity for urea. Response surface analysis was utilized to determine the optimal carbonization conditions, which were found to be 500 °C for 6 h with a heating rate of 15 °C/min. The exceptional adsorption capability of CPB can be ascribed to its porous structure and significant presence of oxygen-containing functional groups, which facilitate a synergistic interaction of physisorption and chemisorption. This adsorption phenomenon aligns with the Harkins–Jura isotherm model and adheres to pseudo-second order kinetics. CPB demonstrates potential as an adsorbent for the elimination of urea from wastewater in an economical and effective fashion.

Batch adsorption of diesel oil in water using saba banana peel biochar immobilized in teabags

Diesel oil contamination is a threat to environment and human health. Many technologies have been developed to address this issue; however, they are costly to be deployed in real-world oil remediation. Adsorption remains to be one of the most economical methods to remove oil from water. Here, we used banana peel biochar (BPBC) immobilized in teabags as an adsorbent for the removal of diesel oil in water. We investigated the adsorption behavior of BPBC under different conditions, examining the influence of adsorbent loading, pH, salinity, and contact time on its efficiency for removing diesel oil in water. Our results show that the sorption capacity of BPBC is significantly affected by the amount of adsorbent used. Lower biochar loadings enhance the sorption capacity due to greater surface area accessibility, while higher loadings lead to decreased efficiency due to pore blockage and reduced surface exposure. Interestingly, the pH of the solution was found to have minimal impact on the sorption process. This is attributed to diesel oil’s hydrophobic and non-polar nature, which leads to its interaction with BPBC being predominantly governed by hydrophobic forces instead of pH-sensitive electrostatic interactions. Salinity emerged as a crucial factor in the adsorption process. An increase in salinity enhances the sorption capacity, likely due to the “salting-out” effect, where higher salt concentrations decrease the solubility of diesel oil, promoting its adsorption onto the biochar surface. Furthermore, the study highlights the importance of contact time, with longer exposure resulting in increased sorption capacity. This trend is explained by the adsorption kinetics, initially characterized by rapid adsorption, followed by a slower, progressive occupation of the biochar’s adsorption sites. The kinetic analysis of the process suggests that the pseudo-second-order model is more suitable, indicating a chemisorption mechanism. The Harkins–Jura isotherm model was identified as the best fit for explaining the isotherm behavior, owing to its capacity to account for the heterogeneous nature of the biochar surface and the formation of multiple adsorbate layers. The optimum conditions for maximum diesel oil removal are as follows: BPBC loading of 0.50 g, a solution pH of 5.00, a salinity concentration of 12,656.57 mg/L, and a contact time of 240 min. Under these conditions, BPBC exhibited an adsorption capacity of 19.04 g/g. In summary, our research establishes BPBC, particularly when contained within teabags, as an efficient and practical adsorbent for diesel oil removal in water. Its effectiveness, superior to other biochar, is mainly due to its porosity and hydrophobic properties. These findings not only enhance our understanding of BPBC’s adsorption capabilities but also underscore its potential for environmental remediation.Graphical

Removal of Iron(II) from Effluents of Steel Mills Using Chemically Modified Pteris vittata Plant Leaves Utilizing the Idea of Phytoremediation

Dargai District Malakand, Pakistan, is a tax-free zone that attracts many industrialists to install their plants in this area. Along with other industries, a number of steel mills are polluting the natural environment of this locality. This study aimed to evaluate heavy metals levels in steel mills effluents and fabricate an efficient adsorbent from the leaves of plants growing on the banks of the drainage lines of the industries and having high phytoremediation capabilities, through chemical modifications. Initially, the effluents were analyzed for heavy metal concentrations, then the leaves of a plant (Pteris vittata) with better phytoremediation capability were chemically modified. The leaves of Pteris vittata were crushed into a fine powder, followed by chemical modification with HNO3, then washed with distilled water, neutralized with NaOH and finally activated through calcium chloride to enhance its biosorption ability, abbreviated as CMPVL. Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), surface area analyzer, energy dispersive X-ray spectroscopy (EDX), and thermal gravimetric analysis (TGA) were used to characterize the CMPVL. The modified leaves in the powdered form were then used for the reclamation of Fe(II) present in the effluents of the mentioned industries. Batch biosorption tests were performed under varied physicochemical conditions of pH (2–9), contact time (10–140 min), temperature (293–333 K), biosorbent dose (0.01–0.13 g), and initial metal concentration (20–300 mg L−1) to optimize the removal of the selected metal. Langmuir, Jovanovic, Freundlich, Temkin, and Harkins–Jura isotherm models were used to assess the equilibrium data. With a high R2 value of 0.977, the Langmuir model offered an excellent match to the equilibrium data. The pseudo-first order, pseudo-second order, power function, intraparticle diffusion, and Natarajan–Khalaf models were applied to experimental kinetics data. With R2 values of 0.999, the pseudo-second order model well fitted the obtained data. The Van’t Hoff equation was used to calculate ΔH°, ΔS° and ΔG° of Fe(II) sorption on CMPVL. The ∆H° and ∆G° were negative, whereas ΔS° was positive, suggesting that the biosorption process was exothermic, favorable, and spontaneous. The selected plant leaves were found to be efficient in the reclamation of iron from the industrial effluents (as the plant has a high natural capability for remediating the selected metal ion) after chemical modification and may be used as an alternative to activated carbon as being a low-cost material and a high phytoremediator of iron metal. Such natural phenomena of phytoremediation should be utilized in obtaining efficient adsorbents for other metals as well.

Removal of reactive black 5 dye by using polyoxometalate-membrane

A POM-membrane was fabricated by immobilizing a keggin type polyoxometalate (POM) H5PV2Mo10O40 onto the surface of microporous flat-sheet polymeric polyvinylidene fluoride (PVFD) membrane using a chemical deposition method. The POM-membrane was characterized by FT-IR, SEM and EDX to confirm existing of the POM onto the membrane surface. The POM-membrane was used to remove an anionic textile dye (Reactive Black 5 named as an RB5) from aqueous phases with a cross-flow membrane filtration and a batch adsorption system. The dye removal efficiency of the POM-membrane using the cross-flow membrane filtration system and the batch adsorption system was about 88% and 98%, respectively. The influence factors such as contact time, adsorbent dosage, pH, and initial dye concentration were investigated to understand the adsorption mechanism of the RB5 dye onto the POM-membrane. To find the best fitting isotherm model, Langmuir, Freundlich, BET and Harkins-Jura isotherm models were used to analyze the experimental data. The isotherm analysis showed that the Langmuir isotherm model was found to the best fit for the adsorption data (R 2=0.9982, qmax=24.87 mg/g). Also, adsorption kinetic models showed the pseudo second order kinetic model was found the best model to fit the experimental data (R2=0.9989, q=8.29 mg/g, C0=15 ppm). Moreover, after four times regeneration with HNO3 acid, the POM-membrane showed high regenerability without losing dye adsorption capacity.

Fly Ash Coated with Magnetic Materials: Improved Adsorbent for Cu (II) Removal from Wastewater.

Fly ash/magnetite material was used for the adsorption of copper ions from synthetic wastewater. The obtained material was characterized by scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDAX), X-ray diffractometer (XRD), Fourier transform infrared spectroscopy (FTIR), Brunauer–Emmett–Teller (BET) surface area, and vibrating sample magnetometer (VSM). Batch adsorption experiments were employed in order to investigate the effects of adsorbent dose, initial Cu (II) concentration and contact time over adsorption efficiency. The experimental isotherms were modeled using Langmuir (four types of its linearization), Freundlich, Temkin, and Harkins–Jura isotherm models. The fits of the results are estimated according to the Langmuir isotherm, with a maximum adsorption capacity of 17.39 mg/g. The pseudo-second-order model was able to describe kinetic results. The data obtained throughout the study prove that this novel material represents a potential low-cost adsorbent for copper adsorption with improved adsorption capacity and magnetic separation capability compared with raw fly ash.

Efficient removal of phenol compounds from water environment using Ziziphus leaves adsorbent

Industrial processes generate toxic organic molecules that pollute environment water. Phenol and its derivative are classified among the major pollutant compounds found in water. They are naturally found in some industrial wastewater effluents. The removal of phenol compounds is therefore essential because they are responsible for severe organ damage if they exist above certain limits. In this study, ground Ziziphus leaves were utilized as adsorbents for phenolic compounds from synthetic wastewater samples. Several experiments were performed to study the effect of several conditions on the capacity of the Ziziphus leaves adsorbent, namely: the initial phenol concentration, the adsorbent concentration, temperature, pH value, and the presence of foreign salts (NaCl and KCl). The experimental results indicated that the adsorption process reached equilibrium in about 4 h. A drop in the amount of phenol removal, especially at higher initial concentration, was noticed upon increasing the temperature from 25 to 45 °C. This reflects the exothermic nature of the adsorption process. This was also confirmed by the calculated negative enthalpy of adsorption (−64.8 kJ/mol). A pH of 6 was found to be the optimum value at which the highest phenol removal occurred with around 15 mg/g at 25 °C for an initial concentration of 200 ppm. The presence of foreign salts has negatively affected the phenol adsorption process. The fitting of the experimental data, using different adsorption isotherms, indicated that the Harkins-Jura isotherm model was the best fit, evident by the high square of the correlation coefficient (R2) values greater than 0.96. The kinetic study revealed that the adsorption was represented by a pseudo-second-order reaction. The results of this study offer a basis to use Ziziphus leaves as promising adsorbents for efficient phenol removal from wastewater.

Removal of hexavalent chromium by ecofriendly raw marine green alga Ulva fasciata: Kinetic, thermodynamic and isotherm studies

The present study investigates the efficiency of marine green macroalga Ulva fasciata to remove Cr(VI) from aqueous solutions. The alga was characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy dispersive X-rays (EDAX) and BET analyses. The effects of various operating parameters such as pH (1–9), biosorbent dose (0.05–0.25 g), initial concentration (10–200 mg/l) and temperature (30–50 °C) were also examined. At concentrations of 10 and 20 mg/l, it was observed that Cr(VI) was completely removed from the solutions after only 5 min contact time. The adsorption experiment data fully showed the applicability of the Harkins-Jura isotherm model. Amongst the applied kinetic models, pseudo-second-order kinetic model was the best fitted one. Thermodynamic parameters (ΔG°, ΔH° and ΔS°) revealed the feasibility of spontaneous random exothermic adsorption. The results indicated the high removal efficiency of Cr(VI) from its aqueous solutions by the raw alga Ulva fasciata because of its low-cost, ecofriendly and promising biosorbent quality.

Comparison of CU(II), MN(II) and ZN(II) adsorption on biochar using diagnostic and simulation models.

With the increase of urbanization and human consumption, the extraction of potentially toxic elements (PTEs) causes higher risk of them to enter sources of human food and potable water. Adsorption has been studied extensively as phenomena to reduce element mobility in both natural and engineered systems. The need to adapt the adsorption models to simulate the adsorption increases as the variety of adsorbents of natural origin is getting bigger and bigger due to their sustainability, availability and low costs. Adsorption of PTEs was analysed in the case of biochar which is a widely studied adsorbent, however, the studies are often limited to standard adsorption equilibrium and kinetic procedures without further analyses into the adsorbate and adsorbent contact zone. Zn(II), Cu(II) and Mn(II) were chosen study due to their nutritional and toxicological features. Diagnostic methods were used to differentiate the metal behaviour during adsorption and dynamic intraparticle model was further employed to simulate the kinetic conditions. Harkins-Jura isotherm model and pseudo-second kinetic model were determined to fit the adsorption of PTEs on biochar. According to the adsorption efficiency and capacity, PTEs fell into the following sequence: Cu(II)>Mn(II)>Zn(II). It was observed that the kinetics of Cu(II) decreased in the solution by about 1.7 times more than of Zn(II) and about 2.3 times more than of Mn(II). Cu(II) decreased faster and more suddenly than Mn(II) and Zn(II) in the solution on the particle surface and in the solution inside the particle.

Freundlich, Langmuir, Temkin, DR and Harkins-Jura Isotherm Studies on the Adsorption of CO2 on Various Porous Adsorbents

Abstract The objective of the study was to prepare low-cost activated carbon from cornelian cherry stones (Cornus mas L.) and compare its adsorption capacities for CO2 with that of commercial multiwalled carbon nanotubes, activated carbon, MCM-41 and four zeolites (silver exchanged, 13X, faujasite type and linde type A). BET, t-plot and DFT methods were used for the characterization of all adsorbent samples based on N2 adsorption-desorption data obtained at 77 K. The produced activated carbon samples (KAC and NAC) were also characterized by scanning electron microscopy (SEM). The adsorption data were evaluated by several isotherm models such as Freundlich, Langmuir, Temkin, DR and Harkins-Jura isotherm models. Langmuir adsorption isotherms constants related to adsorption capacity, Wm were found as 11.496, 6.175, 4.189, 3.986 and 3.50 mmol/g for NAC, KAC, faujasite type zeolit, MCM-41 and AC, respectively. The CO2 adsorption capacities of the silver exchanged, 13X, faujasite type and linde type A zeolites were 10.814, 10.241, 14.608 and 13.343 wt%, respectively. Microporous zeolites showed higher CO2 adsorption capacities than the mesoporous MCM-41 and MWCNT. The CO2 adsorption capacity of commercial activated carbon (AC) was found to be 9.428 wt%, while the CO2 adsorption capacities of activated carbons obtained using NaOH and KOH were found to be 13.685 and 15.057 wt%, respectively. The highest CO2 adsorption capacity of 15.057 wt% was achieved with KAC. It could be confirmed that NaOH or KOH activation plays an important role to determine the porous structure and amount of CO2 adsorbed. Results showed that activated carbon produced from cornelian cherry stones is suitable for the adsorption of CO2 and could be used as a low cost effective adsorbent in the capture of CO2.

Magnetic ethylene diamine-functionalized graphene oxide as novel sorbent for removal of lead and cadmium ions from wastewater samples.

In this paper, magnetic ethylene diamine-functionalized graphene oxide (MDFGO) as a novel sorbent was synthesized and applied for removal of Pb(II) and Cd(II) from real wastewater samples. The morphology and molecular structure of MDFGO were studied by different analytical methods. The effective parameters in adsorption efficiency of Pb(II) and Cd(II) were studied and optimized using experimental design. Under the optimal condition, the effective parameters including pH, sorbent dosage, shaking rate, and adsorption time were 6.2, 33.0mg, 500rpm, and 11min, respectively. Mechanism of adsorption kinetic was investigated using the Lagergren pseudo-first-order, pseudo-second-order, and intraparticle diffusion models. It was found that adsorption of lead and cadmium ions in the MDFGO sorbent followed from pseudo-first-order and pseudo-second-order models, respectively. Thermodynamic parameters (ΔG°, ΔH°, and ΔS°) for the lead and cadmium ions uptake onto the MDFGO sorbent were calculated and indicated that the adsorption processes were spontaneous and endothermic in nature for both cations. In order to investigate the isotherm model for adsorption of Pb(II) and Cd(II), the experimental data were studied using the Langmuir, Freundlich, and Harkins-Jura isotherm models. The results fitted well with Freundlich model for both metal ions. The new sorbent (MDFGO) was applied to remove Pb(II) and Cd(II) from battery wastewater and electroplating wastewater. The removal percentage of Pb(II) and Cd(II) were 99.6±0.5 and 99.4±0.6, respectively, and demonstrated that the new sorbent was very suitable for removal of lead and cadmium ion from the real wastewater samples.

Methylene Blue Adsorption on a Low Cost Adsorbent-Carbonized Peanut Shell.

Carbonized peanut shell (CPS), a low cost adsorbent was investigated for adsorption of methylene blue from its aqueous solution. Some experimental parameters like the effect of initial dye concentration, initial solution pH, phases contact time and temperature were investigated. Langmuir, Freundlich and Harkins-Jura isotherm models were applied to the experimental data and Langmuir model fitted best. Monolayer adsorption capacity was 5.34 mg/g according to the Langmuir model. Adsorption capacity/uptake of CPS was found comparable to the some other adsorbent materials. The kinetic and intra particle diffusion models were applied to the experimental data. The experimental reaction was progressed via pseudo second order kinetic model. The thermodynamic parameters were also evaluated.

Kinetics, Isothermal and Thermodynamic Modelling Studies of Hexavalent Chromium Ions Adsorption from Simulated Wastewater onto Parkia biglobosa-Sawdust Derived Acid-Steam Activated Carbon

The adsorption potential of activated Parkia biglobosa -sawdust carbon for hexavalent chromium ions removal from its wastewater at various operating variables of contact time, initial hexavalent chromium ions concentration, adsorbent particle size and temperature was investigated and evaluated under batch operation mode. Results indicated the impact of operating variables on the adsorption of hexavalent chromium ions. The adsorption process followed Lagergren pseudo first-order kinetics. The adsorption mechanism was film diffusion-controlled. Freundlich and Harkins-Jura isotherm models provided the best correlation ( R 2 = 0.96) of the equilibrium adsorption data. The maximum monolayer adsorption capacity () was found to be 17.54 mg/g. Calculated thermodynamic quantities were evaluated. It was found that the adsorption process was spontaneous, feasible, and endothermic and predominantly of physisorption process with little chemisorption. Therefore, acid-steam activated carbon produced from Parkia biglobosa wood sawdust has potential for application as an effective adsorbent for hexavalent chromium removal from wastewaters

Green synthesis of Ag-Cr-AC nanocomposites by Azadirachta indica and its application for the simultaneous removal of binary mixture of dyes by ultrasonicated assisted adsorption process using Response Surface Methodology

In the present studies the Ag-Cr-AC nanocomposites were synthesized by Azadirachta indica leaves extract. They were inoculated on the amorphous surface of activated carbon. The surface morphology and structural identification was determined by SEM, FTIR and XRD techniques. The simultaneous removal of binary dye system of Reactive Red and Crystal Violet were performed by ultrasonicated assisted adsorption process utilizing Ag-Cr-AC nanocomposites. Central Composite Design (CCD) having 5 factors of time, pH, amount of Ag-Cr-AC (adsorbent), concentrations of Reactive Red (RR) and Crystal Violet (CV) was employed. Response Surface Methodology was applied to study the Optimum Operating Parameters (OOP) for the adsorption process. The current studies showed that they can be efficiently employed to remove the coloured effluent from aqueous media as the simultaneous removal of dyes was observed to be 64.92% and 82.47% for RR and CV dyes respectively. Adsorption equilibrium was studied by Freundlich, Langmuir, Dubinin-Radushkevich, Temkin and Harkins-Jura Isotherm Models. The Langmuir isotherm was observed to be followed by the RR-Ag-Cr-AC system while CV-Ag-Cr-AC followed Harkins-Jura Isotherm model. For the binary system, the removal of CV and RR dyes by the nanocomposites obeyed Harkins-Jura model at temperature of 40°C. Thermodynamics studies affirmed the spontaneous nature of adsorption process. pHpzc was evaluated to be 6.29. The purification cost per cubic meter of the effluent was evaluated to be US$ 85.08. The proposed method might prove to be an efficient and cost effective way to eradicate color from the binary mixture of RR and CV dyes.

Efficient removal of methylene blue dye using mangosteen peel waste: kinetics, isotherms and artificial neural network (ANN) modeling

In this work, mangosteen peel (MP) waste was used as a new biosorbent for removal of methylene blue (MB) dye from aqueous solution. Surface area, surface functional groups, surface charge and surface morphology were analyzed through Brunauer Emmett Teller, Fourier transform infrared, pHzpc and field emission scanning electron microscopy/energy dispersive X-ray spectroscopy techniques, respectively. The major functional groups were -CO, -COO and -OH. Batch adsorption experiments were conducted with varying MP dose (0.01-0.08 g), pH (2-12), contact time (10-60 min), temperature (25°C-45°C) and concentration of MB solution (50-150 mg/L). The study examined the implementation of artificial neural network for the prediction of MB adsorption from aqueous solution by MP, based on 30 experimental sets of batch adsorption study. Optimum number of neurons determined was 4 for Levenberg- Marquardt training algorithm; at which the highest value of R2 and lowest mean square error were found to be 0.997 and 2.972, respectively. Among the various kinetic models applied, the pseudo-second-order kinetic model was identified to be the most suitable to represent the adsorption of MB on the surface of MP. Langmuir, Freundlich, Temkin and Harkins-Jura isotherm models were employed to study the adsorption equilibrium. Langmuir isotherm model was identified as the most suitable. The calculated values of thermodynamic factors, ΔS°, ΔG°, S*, Ea and ΔH°, showed that the adsorption phenomenon is spontaneous, feasible and endothermic in nature. © 2017 Desalination Publications. All rights reserved.

Adsorption of Cu(II) from aqueous phase by Cedar bark

ABSTRACTThe capability of Cedar bark (Cedrus atlantica Manetti) (CB) for the adsorption of Cu(II) from aqueous solutions was examined. Adsorption isotherm and kinetics of Cu(II) by CB were investigated through a number of batch adsorption experiments. The effect of experimental parameters such as initial Cu(II) concentration, adsorbent mass, initial pH and ionic strength on the removal of metal ions was examined. Equilibrium data were fitted to the Langmuir, Freundlich and Harkins–Jura isotherm models. Experimental equilibrium data were best represented by the Langmuir and Harkins–Jura isotherms. The findings revealed that the CB has the potential to be used as an adsorbent for the removal of heavy-metal ions from aqueous solutions.

Comparative Isotherms Studies on Adsorptive Removal of Congo Red from Wastewater by Watermelon Rinds and Neem-Tree Leaves

Equilibrium adsorption studies for detoxification of Congo Red (CR) dye from single component model wastewater by powdered watermelon rinds and neem leaves adsorbents were carried out with the view to test the applicability of the adsorption process to Langmuir, Freundlich, Temkin, Dubinin-Radushkevich and Harkins-Jura isotherm models. The values of correlation coefficient, R2 (0.9359 - 0.9998), showed that all the experimental data fitted the linear plots of the tested isotherm models. Dubinin-Radushkevich’s monolayer maximum adsorption capacity qD (20.72 - 26.06 mg/g) is better than Langmuir’s qm (18.62 - 24.75 mg/g) for both adsorbents with the capacities higher for adsorption on watermelon rind than on neem leaves. Values of Langmuir separation factor (RL) suggest unfavourable adsorption processes (i.e. chemisorption) of the dye on both the adsorbents, while Freundlich constant (nF) indicates unfavourable process only for CR adsorption onto neem leaves. The Dubinin-Radushkevich’s mean free energy of adsorption, E (0.29 - 0.32 kJ/mol), suggests physical adsorption processes. Values for Temkin’s heat of adsorption, bT (-0.95 to 0.74 kJ/mol), also show physical adsorption process.

A Novel Approach to Investigate Adsorption of Crystal Violet from Aqueous Solutions Using Peels of Annona squamosa

An effective and economical adsorbent was prepared from the peels of Annonasquamosafor the removal of crystal violet from aqueous solutions. Adsorption studies were carried out using batch experiments. The dependence of initial dye concentration, pH, contact time, particle size and temperature on the adsorption process was studied. The crystal violet was found to be electroactive and hence electrochemical studies were also performed. The study showed that the equilibrium was achieved within 60 min for the different initial concentrations (10 to 30 mg.l ). The equilibrium adsorption data were analyzed using various isotherm models 1 and they were found to fit Langmuir, Freundlich, Temkin and Harkins-Jura isotherm models in varying orders of magnitude. The maximum dye adsorption capacitiesfor cyclic voltammetry and spectral studiesat 303 K were found to be 5.6818 × 10 A.g (in terms of current)and 5×10 mg.g (in terms of weight),respectively. The data 41 4 1 suggested that the adsorption kinetics was best represented by pseudo-second order kinetic model. The thermodynamic parameters including G, H and S for the adsorption process have also been evaluated using which it was concluded that the process of adsorption was spontaneous and endothermic. The cyclic voltammetricand spectral studies yielded similar results. Furthermore, statistical analysis also showed the absence of any significant difference between the two methods.

Kinetic and isotherm study of Bromothymol Blue and Methylene blue removal using Au-NP loaded on activated carbon

In this research, the efficiency of gold nanoparticle loaded on activated carbon (Au-NP-AC) was used for the removal of Methylene blue (MB) and Bromothymol Blue (BTB) from aqueous solutions. The effect of various parameters such as solution pH, initial dye concentration, amount of Au-NP-AC, and temperature on the extent of dye adsorption was investigated. The performances of two dye adsorption capacities were compared. The adsorption equilibrium data were analyzed using Langmuir, Freundlich, Temkin, Dubinin–Radushkevich, and Harkins-Jura isotherm models. It was seen that Langmuir models represented the equilibrium data well with adsorption capacity of 40.65 and 95.24 mg g−1 for MB and BTB, respectively. Kinetic data revealed that the adsorption of both the dyes on the adsorbent surface followed pseudo–second-order model.

Equilibrium, Thermodynamic and Kinetic Studies on Adsorption of a Basic Dye by Citrullus Lanatus Rind

An effective biosorbent was developed from Citrullus Lanatus Rind and its various biosorption characteristics were studied for removing a basic dye (Crystal Violet) from its aqueous solution. A series of experiments were conducted in a batch system to assess the effects of the system variables such as contact time, biosorbent dosage, pH, initial dye concentration, temperature, particle size and agitation speed. The biosorbent studied exhibits high efficiency for crystal violet adsorption and the equilibrium states could be achieved in 180 min for the different initial concentrations. The equilibrium adsorption data were analyzed by the Langmuir, Freundlich, Tempkin and Harkins-Jura isotherm models. The equilibrium data indicates the following order to fit the isotherms: Freundlich > Tempkin > Harkins-Jura isotherm > Langmuir. The maximum dye adsorption capacity was found to be 11.99 mg/g at 50°C. The biosorption kinetics was found to follow pseudo-second-order rate kinetic model, with good correlation (R = 0.99) and the intra particle diffusion as one 2 of the rate determining steps. Different thermodynamic parameters, like Gibb's free energy (Δ G), enthalpy (Δ H) and entropy (Δ S) of the adsorption process have also been evaluated. The thermodynamic parameters of crystal violet biosorption indicated, the process was spontaneous and endothermic. The results indicated that the biosorbent studied was found to be a promising alternative for the adsorption of crystal violet from aqueous solution.