Experimental Equilibrium Data Research Articles

Enrichment in CO2 Absorption by 2-Methyl Piperazine-Activated Tertiary Amines, Physical Solvents, and Ionic Liquid Systems.

One of the ever-demanding research fields is the development of new solvents with better properties for mitigation of CO2 compared to existing solvents. This work reports the measurement and modeling of CO2 solubility in newly proposed aqueous solvent blends of 2-methyl piperazine with N-methyldiethanolamine (MDEA), sulfolane (TMSO2), and 1-butyl-3-methyl-imidazolium acetate ([bmim] [Ac]). The operating temperature and CO2 partial pressure conditions chosen were 303.2–323.2 K and 2–370 kPa, respectively. Along with this, qualitative 13C NMR and FTIR analysis were also performed to consider the proposed reaction scheme. The experimental vapor–liquid equilibrium data were modeled by a modified Kent–Eisenberg equilibrium model. The equilibrium constants associated with 2-methyl piperazine (2-MPZ) and [bmim] [Ac] deprotonation and carbamate formation reactions were regressed to fit the experimental CO2 solubility data. In addition, the CO2 cyclic capacity and heat of absorption were evaluated for the aq (MDEA + 2-MPZ) blend.

New nanoporous TiO2 with controlled porosities emanated from two concurrent correlative templates as potent adsorbents

In a new attitude, nanoporous titanium oxides (NPTi) were synthesized using tetra heptylammonium bromide (THPAB) for the first time, accompanied simultaneously by the pluronic P123 co-polymer. In addition, varying the amount of the Ti source, the ratio of THPAB:P123 and the binary mixtures of 2-butanol/H2O as solvents led to six different NPTi samples, NPTi-1 to 6, which were synthesized under hydrothermal conditions. The samples were characterized using various techniques, including N2-sorption, XRD, TGA, FT-IR, SEM, TEM and HRTEM. As a result, the surface areas were determined to be in the range between 60 and 170 m2 g−1, while the morphologies were spherical, well-dispersed and nano-sized. Also, the pore diameters and pore volumes varied in the ranges 2.1 to 7.0 nm and 0.1 to 0.3 cm g−1, respectively. The HRTEM image exhibited a d space of 0.35 nm, which is assigned to the crystalline anatase phase. From the XRD results, it was also demonstrated that the structure of the walls were included by the anatase phase. These new nano adsorbents were applied to remove resorcinol (R) and hydroquinone (HQ). The optimal conditions of pH, adsorbent dosage, initial R and HQ concentration, effect of temperature and adsorption time were obtained as 6, 4 mg, 30 mg L−1 and 30 min, respectively. For the titania sample of NPTi-1 (with a pore volume of 0.3 cm g−1), under optimum conditions, the maximum adsorption capacity was 234.8 mg g−1, which was the best adsorbent for removing R and HQ pollutants. The experimental equilibrium data were analyzed using different isotherm models, such as Langmuir, Freundlich, pseudo-first and pseudo-second-order equations.

Theorithecal and experimental study on the thermodynamic parameters and adsorption of methylene blue on “Argania shells” in industrial waters

The present work consists in studying the kinetic, isothermal and thermodynamic properties related to the adsorption of Methylene Blue in industrial waters. The study proposes an package to study the adsorption on the side calculating the parameters: (Langmuir constant KL, Frendlich constant KF, the rate constants for a first order K1, pseudo-second order K2 and second order kinetic K3, and paramètres thermodynamiques) and plotting the trends, through a user-friendly graphical interface. This package aims to save time and avoid errors that may occur when processing experimental results. The experimental study of methylene blue adsorption on Argan shells was performed to verify the performance of this package. The experimental study of the adsorption of methylene blue on the shells of Argan was carried out to verify the performance of this set. It is found that the amount of adsorption of methylene blue on the shells of Argan is 90.96 mg / g for an estimated equilibrium time of 240 min. The correlation coefficient showed that the pseudo-second order kinetic equation best describes the adsorption kinetics. The experimental equilibrium data were analyzed, the Langmuir isotherm provided the best correlation. In addition, the determination of the thermodynamic parameters shows that the reaction is spontaneous and exothermic.

Biosorption of crystal violet by nutraceutical industrial fennel seed spent equilibrium, kinetics, and thermodynamic studies

The present research aims to describe a study that would investigate the practicability of using nutraceutical industrial fennel seed spent (NIFSS) is one of the low-cost types of biosorbent which adsorbs a cationic dye, known as crystal violet (CV), from an aqueous solution. The effects of dye adsorption were also investigated: pH, adsorbent dosage, temperature, particle size, and initial dye concentration. Then the experimental equilibrium data attained was analyzed using isotherm models of Langmuir, Freundlich, Jovanovic, Vieth-Sladek, Brouers-Sotolongo, Redlich-Peterson, and Sips. Hence the use of Film diffusion, Pseudo-first-order, Pseudo-second-order, Dumwald-Wagner and Weber-Morris models for kinetic adsorption studies was done. The maximum experimental adsorption capacity, qe, was determined to be 140 mg g−1 at equilibrium conditions in the lab. The maximum adsorption of 166.73 mg g−1 was predicted by the Brouers-Sotolongo isotherm, which had the closest value of correlation coefficient (R2) of 0.987. Pseudo-second order model fits the kinetic data well in this paper. The thermodynamic parameter values such as ΔG°, ΔH°, and ΔS° demonstrated that the adsorption process was non-spontaneous and exothermic. The lower value of ΔH° shows the physical nature of the process. The CV was adsorbed onto NIFSS, as per the evidence by SEM images and FTIR spectra. The possibility of interaction in the CV-NIFSS system is discussed. To remove CV from an aqueous solution, NIFSS is a fast and effective adsorbent.

Electrochemical synthesis of CNTs–Zn: ZnO@SDS/PEG@Ni2P nanocomposite and its application for ultrasound-assisted removal of methylene blue and investigation of its antibacterial property

In this research, carbon nanotubes modified with CNTs–Zn: ZnO@SDS/PEG@Ni2P nanocomposite (NCs) were applied for removal of methylene blue (MB) following its characterization by XRD, FESEM, and EDS-mapping techniques. Using central composite design (CCD), the relationship between operational parameters like sonication time (1 to 5 min), adsorbent mass (0.1 to 0.2 g), pH (3 to 11), and initial MB concentration (2 to 10 mg L−1) on the efficiency of the understudy system was optimized, and the maximum removal percentage of (100%) was found at 4.0 min sonication, 4 mg L−1 MB, 0.01 g of adsorbent, and pH = 9.0. The fitting of experimental equilibrium data reveals that the Langmuir model (R2 = 0.995) is well suited for evaluating and representing the current adsorption system's actual behavior. Kinetic analyses that match experimental data at different periods show the pseudo-second-order model's (R2 = 0.998) usefulness for properly describing experimental data. Also, Positive ΔH° and ΔS° readings, as well as negative ΔG° values, imply an endothermic, physical, and spontaneous activity. The adsorbent's reusability was also tested over six periods, with a minor decline in adsorbent capacity. In addition, this substance was tested in vitro for antibacterial activity against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) bacteria, addition, candida Albicans (C. Albicans) yeast, while experimental results support the high efficiency of this composite for cleaning and safety improvement of water quality following its application as high-efficiency adsorbent.

Chromium adsorption using Sargassum filipendula algae waste from alginate extraction: Batch and fixed-bed column studies

Chromium is a toxic metal widely used in several industrial activities, being frequently found in industrial effluents. The presence of chromium in its soluble ionic form Cr(III) is related to health risks, damage to living beings and to the environment. In this work, the capture of Cr(III) using alginate extraction residue (RES) from the Sargassum filipendula algae was evaluated to investigate the adsorption properties of this waste material. The study steps included batch and continuous adsorption assays, characterizations, and desorption evaluation. The adsorbent residue was not submitted to pre-treatment steps. The investigation of chromium adsorption and the fluid dynamic study are presented in this work. The equilibrium and thermodynamic studies indicated that the uptake of Cr(III) by the RES occurred spontaneously, endothermic, and energetically favorable on a heterogeneous surface with energetically distinct sites, mainly by chemisorption. The Freundlich and Dubinin-Radushkevich, and pseudo-second order models showed better fit to the equilibrium and kinetic experimental data, respectively. In the continuous fixed-bed system, the breakthrough curves showed a smaller mass transfer zone under flow rate and Cr(III) inlet concentration conditions of 0.5 mL/min and 1.0 mmol/L, respectively. The low desorption percentages corroborate the chemical nature of the bonds involved in adsorption. The best result of 67.5% was obtained with the combined eluent of HCl and CaCl2, both at 1 mol/L. SEM and EDX analyzes showed that ion exchange is involved in the adsorptive process with a reduction in the amount of light ions (Na, Ca, Mg, and K) on the RES surface. The characterization analyzes indicated that hydroxyls are the main group involved in the adsorption of metal that occurred on the surface of the RES.

Adsorption of Zn (II) ions from refinery wastewater by sulfuric acid-modified bentonite: Kinetic and isotherm studies

A local bentonite clay from Maghnia (Algeria) was activated with chemical method characterized and tested for its ability to adsorb Zinc (II) from refinery wastewater. Batch experiments were conducted to study the effects of the main parameters such as contact time, initial metal concentration and agitation speed on the adsorption of Zn (II) by local bentonite clay. Experiences have led to the following results: an adsorption rate of the order of 98 % with operating conditions of pH = 4.5, agitation speed of 400 rpm and temperature of 25 ºC. Pseudo-first-order, pseudo-second-order and intraparticle diffusion models were used to analyze the kinetic data obtained at different concentrations. The pseudo-second-order kinetic model agrees very well with the experimental results. In order to determine the best-fit isotherm, in the studied concentration range of Zn(II) at 25 ºC, the experimental equilibrium data were analyzed using tow adsorption isotherm models: Langmuir and Freundlich models, these two models give a good fit.

Thiabendazole Fungicide Adsorption Onto Four Agricultural Soils Collected from the Loukkos Area of Northwestern Morocco

Abstract A serious environmental problem can arise from the presence of pesticides in soils and waters. Hence, in this study we have carried out the adsorption of the Thiabendazole fungicide onto four soils collected from several areas in Morocco as Larache, Laouamra, Ksar kebir and Tlata drissana. Physicochemical properties, elemental analysis, X-ray diffraction (XRD) were investigated to characterise the four selected soils. The experimental equilibrium data were analysed using Langmuir, Freundlich models. The equilibrium data were best described by a Langmuir model for all adsorbents. The maximum estimated adsorption capacity was 0.747 mg∙g−1, 0.751 mg∙g−1, 0.473 mg∙g−1 and 1.083 mg∙g−1, for Larache, Laouamra, Ksar kebir and Tlata drissana soils, respectively.

Adaptive intermolecular interaction parameters for accurate Mixture Density Functional Theory calculations

The description of fluid mixtures molecular behavior is significant for various industry fields due to the complex composition of fluid found in nature. Statistical mechanics approaches use intermolecular interaction potential to predict fluids behavior on the molecular scale. The paper provides a comparative analysis of mixing rules applications for obtaining intermolecular interaction parameters of mixture components. These parameters are involved in the density functional theory equation of state for mixtures (Mixture DFT EoS) and characterize thermodynamic mixture properties in the bulk. The paper demonstrates that Mixture DFT EoS with proper intermolecular parameters agrees well with experimental mixtures isotherms in bulk: Ar+Ne,CO2+CH4,CO2+C2H6 and CH4+C2H6. However, predictions of vapor–liquid equilibrium (VLE) experimental data for CO2+C4H10 are not successful. Halgren HHG, Waldman – Hagler, and adaptive mixing rules that adjust on the experimental data from the literature are used for the first time to obtain intermolecular interaction parameters for the mixture DFT model. The results obtained provide a base for understanding how to validate the DFT fluid mixture model for calculating thermodynamic properties of fluid mixtures on a micro and macro scale.

Applicability of new sustainable and efficient alginate-based composites for critical raw materials recovery: General composites fabrication optimization and adsorption performance evaluation

Based on the 2020 list of raw materials for the EU, there are 30 critical minerals on the critical raw materials list, among which the rare earth elements group is placed. This study demonstrates a viable approach to the increasing possibility of the critical materials recovery through biosorption. The environmentally friendly biosorbents were prepared modifying calcium alginate with biochar and clinoptilolite. Firstly, the optimization procedure was applied for obtaining new biocomposites. After that the adsorption studies of La(III), Ce(III), Pr(III), and Nd(III) ions as a function of solution pH, biosorbent mass, interaction time, initial metal concentration, temperature, and competing ions presence were carried out using the batch mode. The kinetic studies were analyzed using the pseudo-first order, pseudo-second order, Weber and Morris intraparticle diffusion, Boyd as well as Dumwald-Wagner kinetic models. The experimental equilibrium data were fitted using the Langmuir, Freundlich, Temkin and Dubinin-Radushkevich isotherm models. The thermodynamic functions, i.e. ΔG°, ΔH°, and ΔS° were also determined. Importantly, the biocomposite beads were readily regenerated using diluted mineral acids (exemplary 0.1 mol/dm3 HNO3) and moreover, the adsorption effectiveness was very satisfactory even after six adsorption–desorption cycles (97%). New biocomposites as potential sorbents were characterized with ATR/FT-IR and XPS spectroscopy, SEM, EDX, OM and AFM microscopy, nitrogen adsorption, TG/DTG, CHNS, XRD as well as the sieve analysis and pHpzc measurements. After the interactions of the alginate composites with La(III) ions, a possible sorption mechanism was analyzed by ATR/FT-IR, XPS, and EDX spectroscopy.

Biosorption of Cu(II) ions as a method for the effective use of activated carbon from grape stalk waste: RMS optimization and kinetic studies

ABSTRACT This study was undertaken to examine the effect of such biosorption factors as initial Cu(II) concentration, biosorbent dosage, reaction temperature, contact time and mixing speed on the efficiency of removal Cu(II) ions from wastewater using activated carbon from grape stalk waste. In this case, Response Surface Methodology (RSM) was used in conjunction with a Box–Behnken design of experiments to predict the final Cu(II) concentration (CFin ), while considering the previously mentioned biosorption factors. In an attempt to obtain the maximum removal of final Cu(II) concentration, while minimizing energy consumption, the Multi-Response Surface Methodology (MRS) was used. Three possible optimizations were proposed for the maximum elimination of final Cu(II) in this case. The maximum (100 mg/L), minimum (2 mg/L) and intermediate (51 mg/L) values of the study were used for the initial Cu(II) concentration. The optimal values that were reached were 92.21% when the initial copper concentration was 51 mg/L and the activated carbon dose, temperature, mixing speed and reaction time, were, respectively, 0.895 g/L, 20.036°C, 105.313 rpm and 30.181 s. Also, in regard to thermodynamic studies, the experimental equilibrium data provided a good fit using the Freundlich model, whereas the kinetic data were efficiently by the pseudo-second order. These results support the use of grape stalk waste in the production of activated carbon for the removal of Cu(II) ions from water. This could help to improve the economics of treating wastewater.

Adsorption of brilliant green dye onto activated carbon prepared from cashew nut shell by KOH activation: Studies on equilibrium isotherm

Activated carbon from cashew nut shell via a potassium hydroxide (KOH) at 600 °C in an N2 atmosphere and their characteristics using FT-IR, XRD, SEM with EDS, and BET analysis was investigated. The cashew nut shell activated carbon obtained by KOH activation with a CNS/KOH ratio of 1:1 at 600 °C (N2 atmosphere) for 2 h had the highest surface area (407.80 m2/g) as compared to other ratio samples. Amongst, CNS/KOH ratios of 1:1 sample are used for the adsorbent, they are effects of contact time, pH, adsorbent dose, and initial dye concentration on brilliant green (BG) removal efficiency were studied. Moreover, the Langmuir and Freundlich adsorption models consisted utilized to affirm the adsorption isotherms. They are, best fitting for BG experimental equilibrium data was achieved with the Langmuir isotherm, giving a maximum BG adsorption capacity of 243.90 mg/g.

Scavenging of hexavalent chromium from aqueous solution by Macadamia nutshell biomass modified with diethylenetriamine and maleic anhydride

Based on the premise that aqueous anions of hexavalent chromium (Cr(VI)) are capable of electrostatic interaction with cationic and polar active sites, acid-washed Madacamia nutshell biomass was sequentially treated with diethylenetriamine (DETA) and maleic anhydride (MA) to graft poly(diethylenetriamine–co–maleic anhydride). By displaying a new peak at 1685 cm−1 ascribed to amide CO stretching vibrations, Fourier transform infrared spectroscopy highlighted the formation of amide groups through reaction of DETA with carboxyl groups on the biomass surface. Scanning electron microscopic images of the MA-modified biomass displayed polymeric growths attributed to copolymerization of DETA with MA. The polar and ionizable amide and amine groups of the grafted copolymer endowed the adsorbent with Cr(VI) removal capabilities over a wide pH range demonstrated by removal efficiencies between 70.9% and 81.7% in the pH 1.6 to pH 10.0 range for the treatment of 20 mL solutions containing 100 mg L−1 Cr(VI) with 200 mg of adsorbent. Conformity of the adsorption isotherm data to the Freundlich model revealed the heterogeneous nature of the adsorbent surface, which comprised a variety of functional groups capable of interaction with Cr(VI) species in solution. The Sips isotherm model provided the best fit to the equilibrium experimental data, and the adsorption capacity was 779.1 mg g−1 at pH 1.6, room temperature and an adsorbent dosage of 5.0 g L−1. The findings indicate that Cr(VI) adsorption onto diethylenetriamine and maleic anhydride modified Madacamia nutshell biomass is a promising option for Cr(VI) removal from aqueous solutions.

Comparative Evaluation of the Adsorption Performance of Citric Acid-Treated Peels of Trapa natans and Citrullus lanatus for Cationic Dyes Degradation from Water

Various chemicals were explored in chemical combinations with two selected agrowastes in order to optimize, enhance, and improve their biosorption potential for the optimal and effective eradication of noxious, carcinogenic, and malignant cationic and basic dyes from wastewater. In this project, environmentally safe, economic, inexpensive, and widely available peels of Trapa natans (TP) and Citrullus lanatus (CP) were collected, dried, and pretreated with citric acid, revealing promising results. FT-IR and SEM characterizations of chemically changed biosorbents (C-TP and C-CP) have evidenced the presence of more secondary adsorption sites on their surfaces. These acid-modified biosorbents were employed to eliminate the hazardous and toxic basic dyes such as Rhodamine B (RAD) and Brilliant Green Dye (BLG) in batch mode processing. The Langmuir model was best fitted to equilibrium experimental data as compared to Freundlich and Temkin isothermal mathematical models with Qmax of 15.63 and 27.55 mg/g for RAD using C-TP and C-CP, respectively, whereas, for BLG on C-TP and C-CP, it was 128 and 189 mg/g, respectively. Therefore, the mechanism is related to chelation and ion exchange modes between adsorbate molecules and adsorbent surfaces, leading to homogeneous and monolayer adsorption and following pseudo-2nd-order kinetics in the best way. Thermodynamic parameters such as ΔG0, ΔS0, ΔH0, and ΔE0 are determined statistically for the adsorption performance of both novel chemically mutant biosorbents, which reflect that biosorption mechanisms are exothermic as well as spontaneous.

Removal of Cylindrospermopsin by Adsorption on Granular Activated Carbon, Selection of Carbons and Estimated Fixed-Bed Breakthrough

Climate change and the increase in the availability of nutrients in aquatic environments have increased the occurrence of cyanobacterial blooms which can produce cyanotoxins such as cylindrospermopsin (CYN). Activated carbon adsorption have been proved to be efficient for CYN removal. In the present study, a carbon with high CYN adsorption capacity was identified between two granular activated carbons. For this carbon was estimated the operating time of a full-scale granular activated carbon column under different empty bed contact times (EBCT). The fixed-bed breakthrough was estimated using the Homogeneous Surface Diffusion Model (HSDM). Wood carbon showed greater capacity to remove CYN. The experimental equilibrium data best fitted Langmuir isotherm model, in which wood carbon had a maximum adsorption capacity of 3.67 μg/mg and Langmuir adsorption constant of 0.2791 L/μg. The methodology produced satisfactory results where the HSDM simulated the fixed-bed breakthrough with a coefficient of determination of 0.89, to the film diffusion coefficient (Kf) of 9 × 10−6 m/s and surface diffusion coefficient (Ds) of 3 × 10−16 m2/s. It was observed that the increase in EBCT promotes a reduction in the carbon use rate. The best carbon use rate found was 0.43 kg/m3 for a EBCT of 10 min and breakthrough time of 183.6 h.

Novel metal based nanocomposite for rapid and efficient removal of lead from contaminated wastewater sorption kinetics, thermodynamics and mechanisms

A sol–gel method was utilized to prepare a novel nanocomposite adsorbent (nMgO/bentonite) and was tested for Pb(II) removal from aqueous solutions. The produced nanocomposite was investigated using, SEM–EDX, XRD, and FTIR analyses before and after Pb adsorption. Adsorption equilibrium and kinetic experiments were run in batch system under different conditions of pH, adsorbent dose, competitive cations, contact time and temperature. The results exhibited rapid Pb(II) adsorption by the nanocomposite in the first five min. Experimental lead adsorption equilibrium and kinetics data fitted well to Langmuir and power function models, respectively as indicated from the lowest standard error (SE) values. The calculated Langmuir maximum adsorption capacity (qmax) value of nanocomposite (75 mg g−1) was 4.5 times higher than that of bentonite (16.66 mg g−1). Moreover, the highest quantity of Pb(II) uptake was achieved at temperature of 307 K and pH 9. The Langmuir sorption capacity of the nanocomposite for Pb(II) increased from 75 to 145 mg g−1 with increasing temperature from 287 to 307 K. The thermodynamic parameters of Pb(II) adsorption by the nanocomposite affirm the spontaneous and endothermic nature of the adsorption process. Lead adsorption mechanisms by the nanocomposite were proposed and discussed.

Physicochemical, structural, and adsorption properties of chemically and thermally modified activated carbons

In this work, granular activated carbon (GAC1240W Norit N.V.) was chemically and thermally modified to diverse its acid-base character. The main aim of this work was to assess the efficiency of surface modifications of activated carbons (ACs) concerning studying the differentiation of their affinity towards aromatic organic compounds of various properties. For this purpose, the comprehensive characteristics of oxidized activated carbon (AC-OX) and oxidized thermally modified carbons at 180, 280, 380, 480, 640, and 800 °C (AC-OX, AC-OX-180, 280, 380, 480, 640, and 800) were analyzed using several analytical techniques:low-temperature nitrogen sorption (porosity characteristics), potentiometric titration of suspension (SPT) (acid-base properties), X-ray photoelectron spectroscopy (XPS) (quality and quantity analysis of elements), thermal analysis (TA) coupled with mass spectrometry (MS) (materials thermal stability, identification of gaseous products emitted during thermal decomposition). To verify the applicability of adsorbents for removing selected organic compounds, the equilibrium and kinetic experimental data were measured and analyzed by applying various equations and models.

Doxycycline Adsorptive Interaction with Mesoporous MCM-41: Kinetic and Isotherm Modelling with Thermodynamics

Antibiotics are bio-accumulating and persistent. its inappropriate disposal can affect human health and aquatic fauna. Development of antimicrobial resistance has been announced as one of the top ten threats to global health in 2019. In this study, Doxycycline adsorption on to MCM-41 (not reported earlier) was studied. Adsorbent dose (m), Doxycycline solution pH, adsorption time (t) and temperature (T) were considered as process parameters, and %Doxycycline removal and adsorption capacity were measured as responses of the adsorption. Parameters (m, pH and t) interaction, modelling and optimization for %Doxycycline removal and adsorption capacity was performed using Box Behnken Design. Based on this, a suitable model equation and adsorption mechanism was suggested. At optimized parameters, kinetics and adsorption rate controlling mechanism was studied. Further, various isotherm models (Freundlich, Langmuir and Redlich-Peterson) were studied to represent the adsorption equilibrium experimental data. the optimum process parameters were found to be pH = 7.3, m = 0.02 g/L and t = 20 min. At optimized parameters, very high %Doxycycline removal of 99% with 2425 mg/g adsorption capacity was observed (max 835.5 mg/g adsorption capacity for Doxycycline is reported in literature). Thermodynamics study revealed enthalpy (ΔH°) = 23.02 kJ/mol confirming DCL physisorption on MCM-41.

Application of biorefinery by-product of Nigella sativa L. herb for green treatment of synthetic dye impurity in aquatic environment: a circular economy based approach to water purification

In this work, the performance of residual biomass of Nigella sativa L. plant from the process of bio-oil production toward the green removal of synthetic dye pollution from aquatic medium was systematically studied for the first time based on the circular economy strategy. The characterization of material was performed using Electron Microscope of Scanning and Infrared Spectrometer of Fourier Transform. The main process variables like pH, biosorbent amount, synthetic dye loading, and contact duration were optimized by the batch biosorption experiments to achieve the maximum remediation yield. The analyses of kinetics, equilibrium, and thermodynamics were conducted to understand the possible mechanism of purification. The experimental dynamics and equilibrium data were in better agreement with the pseudo-second-order and Langmuir models. For the targeted model synthetic dye compound (C. I. Basic Red 46), the biosorption capacity was obtained as 136.2 mg g−1 at the optimized conditions of pH of 8, biosorbent amount of 10 mg (100 mg L−1), synthetic dye loading of 30 mg L−1, and duration of 360 min. The treatment process was favorable, spontaneous, and physical. The characterization operation showed that the dye molecules were restrained on the rough surface of biosorbent. This study reveals that the reuse of herbal oil refinery residue as a biosorbent can present an economic, efficient, and eco-friendly option for the remediation of synthetic dye pollution in aqueous medium.

Equilibrium Biosorption of Zn2+ and Ni2+ Ions from Monometallic and Bimetallic Solutions by Crab Shell Biomass

This work explored the technical feasibility of using crab shell (CS) as a promising, low-cost biosorbent to individually and simultaneously remove Zn2+ and Ni2+ from aqueous solutions. It was found that in both monometallic and bimetallic systems, Zn2+ and Ni2+ biosorption by CS was strongly dependent on the solution pH, with the optimum biosorption occurring at a pH of 6.0 for both heavy metals. The obtained isotherms for Zn2+ and Ni2+ biosorption onto CS in monometallic and bimetallic systems demonstrated that CS has a higher affinity for Zn2+ than for Ni2+. The experimental equilibrium data for the bimetallic system revealed that when one heavy metal is present in the system, there is a decrease in the equilibrium biosorption capacity for the other heavy metal; therefore, the combined action of Zn2+ and Ni2+ was antagonistic. The Sips and Redlich–Peterson isotherm models best fitted the equilibrium biosorption data for Zn2+ and Ni2+ in the monometallic systems, while the modified Sips model best fitted the binary biosorption equilibrium data. DRIFTS analyses indicated that carbonate ion, chitin, and proteins are mainly involved in the biosorption of Zn2+ and Ni2+ by CS from aqueous solutions, as confirmed using a range of analytical techniques.