Ionic solid-impregnated sulphate-crosslinked chitosan for effective adsorption of hexavalent chromium from effluents

Microwave-assisted tetrabutyl ammonium-impregnated sulphate-crosslinked chitosan was synthesized for enhanced adsorption of hexavalent chromium. The adsorbent obtained was extensively characterized using Fourier transform infrared, X-ray diffraction, scanning electron microscopy and energy-dispersive X-ray studies. Various isotherm models such as Langmuir, Freundlich and Dubinin–Radushkevich were studied to comprehend the adsorption mechanism of hexavalent chromium by the adsorbent. Maximum adsorption capacity of 225.9 mg g^?1 was observed at pH 3.0 in accordance with Langmuir isotherm model. The sorption kinetics and thermodynamic studies revealed that adsorption of hexavalent chromium followed pseudo-second-order kinetics with exothermic and spontaneous behaviour. A column packed with 1 g of adsorbent was found to give complete adsorption of Cr(VI) up to 900 mL of 200 mg L^?1 solution which discerns the applicability of the adsorbent material for higher sample volumes in column studies. The effective adsorption results were obtained due to both ion exchange and ion pair interaction of adsorbent with hexavalent chromium. Greener aspect of overall adsorption was regeneration of the adsorbent which was carried out using sodium hydroxide solution. In the present study, the regenerated adsorbent was effectively reused up to ten adsorption–desorption cycles with no loss in adsorption efficiency.     

Preparation and characterization of biosorbents and copper sequestration from simulated wastewater

This paper reports the potential of chemically treated wood chips to remove copper (II) ions from aqueous solution a function of pH, adsorbent dose, initial copper (II) concentration and contact time by batch technique. The wood chips were treated with (a) boiling, (b) formaldehyde and (c) concentrated sulphuric acid and characterized by Fourier transform infrared spectroscopy, scanning electron microscopy and energy dispersive analysis X-ray. pH 5.0 was optimum with 86.1, 88.5 and 93.9 % copper (II) removal by boiled, formaldehyde-treated and concentrated sulphuric acid-treated wood chips, respectively, for dilute solutions at 20 g L^?1 adsorbent dose. The experimental data were analysed using Freundlich, Langmuir, Dubinin–Radushkevich and Temkin isotherm models. It was found that Freundlich and Langmuir models fitted better the equilibrium adsorption data and the adsorption process followed pseudo-second-order reaction kinetics. The results showed that the copper (II) is considerably adsorbed on wood chips and it could be an economical option for the removal of copper from aqueous systems.     

Chemical treatment of teff straw by sodium hydroxide,phosphoric acid and zinc chloride: adsorptive removal of chromium

In this study, teff (Eragrostis tef) straw has been chemically treated and tested as an adsorbent for Cr(VI) removal. Chemically treatment of teff straw was done by NaOH, H₃PO₄ and ZnCl₂ solutions. Scanning electron micrograph and X-ray diffraction were used for anatomical characterization, whereas Fourier transform infrared spectroscopy was used for surface change characterization of adsorbents. Effects of different experimental parameters like pH (2–12), initial Cr(VI) concentration (100–900 mg/L), adsorbent dose (2.5–20 g/L), contact time (15–360 min) and temperature (288–318 K) were studied. Temperature increment was found to stimulate the adsorption process. Langmuir isotherm was found to give better representation over wide range of temperature for untreated, H₃PO₄- as well as ZnCl₂-treated teff straw, and Freundlich isotherm best represented the isotherm data for NaOH-treated teff straw. Maximum Cr(VI) adsorption capacity of untreated, NaOH-, H₃PO₄- and ZnCl₂-treated teff straw was found to be 86.1, 73.8, 89.3 and 88.9 mg/g, respectively. Respective values of average effective diffusion coefficient (D _e) were found to be 2.8 × 10^?13, 2.59 × 10^?14, 1.32 × 10^?13 and 1.14 × 10^?13 m²/s, respectively. The negative value of ΔG _o for all the adsorbents indicates Cr(VI) spontaneous adsorption. Isosteric heat of adsorption (ΔH _st,a) was found to vary with surface coverage (θ). ΔH _st,a increased for untreated, H₃PO₄- and ZnCl₂-treated teff straw, and decreased steadily with θ for NaOH-treated teff straw.     

Adsorption kinetics and thermodynamics of organophosphorus profenofos pesticide onto Fe/Ni bimetallic nanoparticles

Bimetallic Fe/Ni nanoparticles were synthesized and used for the removal of profenofos organophosphorus pesticide from aqueous solution. These novel bimetallic nanoparticles (Fe/Ni) were characterized by scanning electron microscopy, energy-dispersive X-ray analysis spectroscopy, X-ray diffraction, and Fourier transform infrared spectroscopy. The effect of the parameters of initial pesticide concentration, pH of the solution, adsorbent dosage, temperature, and contact time on adsorption was investigated. The adsorbent exhibited high efficiency for profenofos adsorption, and equilibrium was achieved in 8 min. The Langmuir, Freundlich, and Temkin isotherm models were used to determine equilibrium. The Langmuir model showed the best fit with the experimental data (R ² = 0.9988). Pseudo-first-order, pseudo-second-order, and intra-particle diffusion models were tested to determine absorption kinetics. The pseudo-second-order model provided the best correlation with the results (R ² = 0.99936). The changes in the thermodynamic parameters of Gibb’s free energy, enthalpy, and entropy of the adsorption process were also evaluated. Thermodynamic parameters indicate that profenofos adsorption using Fe/Ni nanoparticles is a spontaneous and endothermic process. The value of the activation energy (E _a = 109.57 kJ/mol) confirms the nature of the chemisorption of profenofos onto Fe/Ni adsorbent.     

Fast,green and effective chromium bio-speciation using <Emphasis Type="Italic">Sepia pharaonis</Emphasis> endoskeleton nano-powder

The development of a fast, effective, simple and low-cost procedure for chromium speciation is an analytical challenge. In this work, a new and simple method for speciation and determination of chromium species in different matrices was developed. Sepia pharaonis endoskeleton nano-powder was used as an adsorbent for the dispersive micro-solid-phase extraction. Finally, the desorbed chromium was determined using a graphite furnace atomic absorption spectrometer. The experimental results showed that Cr(III) could be quantitatively extracted by the adsorbent, while Cr(VI) adsorption was negligible. Concentrated H₂SO₄ and ethanol reduced Cr(VI)–Cr(III), and total chromium content was assessed as Cr(III). Then, the Cr(VI) concentration in the sample was calculated as the difference. The optimum conditions were obtained in terms of pH, adsorbent amount, contact time, and type, concentration and volume of eluent. Under the optimum conditions that involved the speciation of chromium ions from 25 mL of the water samples at pH 7.0 using 0.025 g of the adsorbent with contact time of 5 min, the method was validated in terms of linearity, precision and accuracy. The calibration curve was linear over the concentration range of 0.01–25.00 μg L^?1 for Cr(III). The obtained limit of detection for the proposed method was 0.003 µg L^?1. The maximum adsorption capacity of the adsorbent was found to be 995.57 mg g^?1. The proposed method was validated by the speciation of Cr(III) and Cr(VI) in different real water and wastewater samples with satisfactory results.     

Kinetic and equilibrium study of Ni(II) sorption from aqueous solutions onto Peganum harmala-L

In this study, the adsorption behavior of Ni(II) in an aqueous solution system using natural adsorbent Peganum harmala-L was measured via batch mode. The prepared sorbent was characterized by scanning electron microscope, Fourier transform infrared spectroscopy, N₂ adsorption–desorption and pH_zpc. Adsorption experiments were carried out by varying several conditions such as contact time, metal ion concentration and pH to assess kinetic and equilibrium parameters. The equilibrium data were analyzed based on the Langmuir, Freundlich, Temkin and Dubinin–Radushkevich isotherms. Kinetic data were analyzed using the pseudo-first-order, pseudo-second-order and intra-particular diffusion models. Experimental data showed that at contact time 60 min, metal ion concentration 50 mg/L and pH 6, a maximum amount of Ni(II) ions can be removed. The experimental data were best described by the Langmuir isotherm model as is evident from the high R ² value of 0.988. The adsorption capacity (q _m) obtained was 68.02 mg/g at an initial pH of 6 and a temperature of 25 °C. Kinetic studies of the adsorption showed that equilibrium was reached within 60 min of contact and the adsorption process followed the pseudo-first-order model. The obtained results show that P. harmala-L can be used as an effective and a natural low-cost adsorbent for the removal of Ni(II) from aqueous solutions.     

Effective removal of zinc from an aqueous solution using Turkish leonardite–clinoptilolite mixture as a sorbent

In this study, the feasibility of using a low-cost adsorbent mixture composed of leonardite (L) and clinoptilolite (C) was evaluated by batch adsorption method using different parameters such as mixing ratio, contact time, pH, temperature, and adsorbent amount for the removal of Zn (II) ions from an aqueous solution. The adsorbents were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, and Raman spectroscopy. Additionally, leonardite–clinoptilolite mixture was analyzed by scanning electron microscopy coupled with energy dispersive X-ray. The Zn (II) adsorption along with an unprecedented adsorption capacity of 454.55 mg g^?1 for unmodified natural sorbents was obtained by mixing leonardite and clinoptilolite (LC) without any pretreatment at a ratio of 3:1, using 0.1 g of sorbent at a pH 6, for 2 h of contact time. The experimental data showed a good fit for the Langmuir isotherm model. The thermodynamic parameters revealed that the present adsorption process was spontaneous and exothermic in nature (25–50 °C). The kinetic results of the adsorption showed that the Zn (II) adsorption onto the LC follows pseudo-second-order model. The resultant LC mixture has an excellent adsorption capacity of a Zn (II) aqueous solution, and data obtained may form the basis for utilization of LC as an unpretreated low-cost adsorbent for treatment of metalliferous industrial wastewater.     

Synthesis of Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>-loaded porous carbons developed from rice husk for removal of arsenate from aqueous solution

A simple one-step synthetic approach using rice husk has been developed to prepare magnetic Fe₃O₄-loaded porous carbons composite (MRH) for removal of arsenate (As(V)). The characteristics of adsorbent were evaluated by transmission electron microscope, scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, Brunauer–Emmett–Teller analysis, and thermogravimetric analysis. On account of the combined advantages of rice husk carbons and Fe₃O₄ nanoparticles, the synthesized MRH composites showed excellent adsorption efficiency for aqueous As(V). The removal of As(V) by the MRH was studied as a function of contact time, initial concentration of As(V), and media pH. The adsorption kinetics of As(V) exhibited a rapid sorption dynamics by a pseudo-second-order kinetic model, implying the mechanism of chemisorption. The adsorption data of As(V) were fitted well to the Langmuir isotherm model, and the maximum uptake amount (q _m ) was calculated as 4.33 mg g^?1. The successive regeneration and reuse studies showed that the MRH kept the sorption efficiencies over five cycles. The obtained results demonstrate that the MRH can be utilized as an efficient and low-cost adsorbent for removal of As(V) from aqueous solutions.     

Adsorption of hexavalent chromium onto activated carbon derived from <Emphasis Type="Italic">Leucaena leucocephala</Emphasis> waste sawdust: kinetics,equilibrium and thermodynamics

The adsorptive removal of Cr(VI) was studied using activated carbon derived from Leucaena leucocephala (ACLL). The physico-chemical properties of ACLL were determined using proximate analysis and N₂ BET surface area analysis. The N₂ BET surface area of ACLL was determined to be 1131 m² g^?1. The point of zero charge (pH_pzc) of 5.42 indicated that ACLL surface was positively charged for pH below the pH_PZC, attracting anions. The effect of experimental operating parameters such as time of contact, ACLL dose, pH, initial concentration and temperature was investigated. The optimum values of parameters such as concentration of 100 mg L^?1, 300 mg of ACLL dose, time of contact of 60 min, pH of 4 indicated the maximum Cr(VI) uptake of 13.85 mg g^?1. The pseudo-second-order kinetic model best fitted with the Cr(VI) adsorption data. Adsorptive removal of Cr(VI) onto ACLL satisfactorily fitted in the order of Redlich–Peterson > Freundlich > Langmuir > Temkin adsorption isotherm model. The thermodynamic parameters showed the adsorption of Cr(VI) onto ACLL was an endothermic and spontaneously occurred process.     

Removal of chromate from wastewater using amine-based-surfactant-modified clinoptilolite

This study presents the results of chromate adsorption upon organically modified clinoptilolite obtained by the treatment of Bigadic clinoptilolite with surfactants in primary amine structure, namely 1-dodecylamine, 1-hexadecylamine and oleylamine. Natural and organo-clinoptilolites were characterized by X-ray diffraction, thermal gravimetry and Fourier transform infrared spectrometry which proved the integration of amine groups followed by the order oleylamine > 1-hexadecylamine > 1-dodecylamine. Organo-clinoptilolites were tested for their efficacy in chromate removal under base case conditions which implied 100 ppm initial concentration, pH 4.0, 10 g l^?1 adsorbent dose and at 298 K. Results showed that amine loading induced chromate removal reaching up to 90 % for oleylamine-modified clinoptilolite. Experimentation was continued to determine the effects of pH, adsorbent dosage and initial concentration on chromate adsorption. Accordingly, maximum removal of 94.0 % was attained with 14 g l^?1 of oleylamine-modified clinoptilolite, from Cr(VI) solution of 100 ppm initially at pH 3.0. Langmuir isotherm described the adsorption of chromate on oleylamine-modified clinoptilolite with 96.4 % consistency. Maximum theoretical uptake capacity was calculated as 6.72 mg g^?1. Kinetic data were consistent with pseudo-second-order model with the controlling steps being film and pore diffusions.     

Advantage of almond green hull over its resultant ash for chromium(VI) removal from aqueous solutions

The discharge of industrial effluents containing hexavalent chromium can be very harmful for the environment. Therefore, Cr(VI) should be removed from contaminated water, and especially from wastewater, to prevent its discharge into the environment. This study is aimed at analyzing the factors that affect the removal of Cr(VI) with the use of almond green hull and ash adsorbent. The effects of pH (2–10), adsorbent dose (2–24 g/L), Cr(VI) concentration (10–100 mg/L), exposure time (1–60 min), and temperature (5–50 °C) were examined. The surface morphology, pore size of adsorbent surfaces were characterized with SEM, EDX, FTIR. Maximum removal occurred at pH = 2. Results showed that the removal yield increased with the rise of exposure time and temperature. The data indicate that due to limited site on adsorbent surface, the removal efficiency decreased as initial Cr(VI) concentration increased. When the adsorbent dose was increased, the removal yield increased in the case of the bioadsorbent as well; however, in the ash adsorbent, there was an increase followed by a decreasing trend. The study highlights that almond green hull can be more efficient than its ash in the removal of Cr(VI) from aqueous solution. As a general result of study, it can be argued that almond green hull bioadsorbent and the obtained carbon are able to remove Cr(VI) from aqueous solutions; thus, they can be used as efficient and economical substitutes for existing adsorbents like activated carbon, for the removal of chromium from polluted aqueous solutions.     

Comparative study on adsorption of chromium(VI) from industrial wastewater onto nature-derived adsorbents (brown coal and zeolite)

The removal of hexavalent chromium from wastewater streams has received an considerable attention in recent years, since it can cause harmful effects on the environment. Several approaches, including adsorption, are recognized to tackle this problem, but unfortunately most of these processes are impressed with practical conditions of the experiments. The main objective of this study was to recognize applicable conditions for Cr(VI) removal from an industrial drainage using nature-derived adsorbents (brown coal and modified zeolite) and to make the process more adaptive by using adsorbents conjointly. Batch experiments were carried out by agitating Cr(VI) stock solution with adsorbents at room temperature. The influence of main operating parameters was explored, and the best proportion of the adsorbents was determined. Maximum sorption of Cr(VI) onto brown coal was observed at pH = 4 by adding 60 g L^?1 adsorbent to contaminated solution. In case of using zeolite, the modification process was required, and the pH indicated a weak influence in a wide range (2–8). Optimum dosage of modified zeolite for Cr(VI) removal was 10 g L^?1. The hybrid application of adsorbents with the mass ratio of brown coal/modified zeolite at (3:1) was capable of removing more than 99% of Cr(VI) from contaminated wastewater in the natural pH range of the wastewater. The adsorption of Cr(VI) by brown coal and modified zeolite followed Langmuir and Freundlich isotherm models, respectively. Sorption of Cr(VI) onto both brown coal and modified zeolite fitted well to pseudo-second-order rate reaction.     

Formation of one-dimensional composites of poly(<Emphasis Type="Italic">m</Emphasis>-phenylenediamine)s based on <Emphasis Type="Italic">Streptomyces</Emphasis> for adsorption of hexavalent chromium

Here, a novel one-dimensional composite of poly(m-phenylenediamine)s coating on filamentous Streptomyces was successfully constructed via a controllable polymerization reaction. The synthesized composites were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. Their adsorption isotherm and kinetics for aqueous hexavalent chromium were also systematically examined. The results of scanning electron microscopy analysis indicated that the obtained composites based on Streptomyces were showed a uniform and stable one-dimensional morphology with distinct core–shell configuration. Moreover, the Langmuir isotherm model (R ² > 0.96) and pseudo-second-order equation (R ² = 0.9996) described well the equilibrium adsorption behavior and kinetics of hexavalent chromium adsorption by the composites. In addition, bath adsorption experiments demonstrated the highest adsorption capacity of hexavalent chromium by the composites reached 320.03 mg g^?1 in an acid solution, which was 5.6 times as that of the pure Streptomyces filaments. The results of Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy analyses suggested that the adsorption of hexavalent chromium by the composites possibly involved the protonation, redox, and chelation reactions. Therefore, a promising application of these composites in treating acid hexavalent chromium-contaminated wastewater is expectable.     

Comparative study of the absorptive potential of raw and activated carbon <Emphasis Type="Italic">Acacia nilotica</Emphasis> for Reactive Black 5 dye

Acacia nilotica was used for the adsorption of Reactive Black 5 (RB5) dye from an aqueous solution. Both the raw and activated (with H₃PO₄) carbon forms of Acacia nilotica (RAN and ANAC, respectively) were used for comparison. Various parameters (including dye concentration, contact time, temperature, and pH) were optimized to obtain the maximum adsorption capacity. RAN and ANAC were characterized using Fourier transform infrared spectroscopy, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The maximum experimental adsorption capacities for RAN and ANAC were 34.79 and 41.01 mg g^?1, respectively, which agreed with the maximum adsorption capacities predicted by the Langmuir, Freundlich, and Dubinin–Radushkevich equilibrium isotherm models. The adsorption data of ANAC showed a good fit to the isotherm models based on the coefficient of determination (R ²): Langmuir type II (R ² = 0.99) > Freundlich (R ² = 0.9853) > Dubinin–Radushkevich (R ² = 0.9659). This result suggested monolayer adsorption of RB5 dye. The adsorption of RB5 dye followed pseudo-second-order kinetics. The RAN adsorbent reflected an exothermic reaction (enthalpy change, ΔH = ?0.006 kJ mol^?1) and increased randomness (standard entropy change, ΔS = 0.038 kJ mol^?1) at the solid–solution interface. In contrast, ANAC reflected both exothermic [?0.011 kJ mol^?1 (303–313 K)] and endothermic [0.003 kJ mol^?1 (313–323 K)] reactions. However, the ΔS value of ANAC was lower when the RB5 adsorption increased from 313 to 323 K. The negative values for the Gibbs free energy change at all temperatures indicated that the adsorption of RB5 dye onto RAN and ANAC was spontaneous in the forward direction.     

Equilibrium studies on removal of lead (II) ions from aqueous solution by adsorption using modified red mud

In the present experimental study, solid waste was used as an adsorbent and the effectiveness of the adsorbent was increased by novel treatment methods. Red mud, acid-treated activated red mud and iron oxide-coated acid-treated activated red mud were used for the removal of lead (II). The structural and functional groups were identified to confirm the removal of lead (II) by powder X-ray diffraction and Fourier transform infrared spectroscopy analyses. The enhancement of surface area was confirmed by Brunauer–Emmett–Teller analysis. Batch adsorption experiment was also conducted, and various parameters such as the effect of adsorbent dosage, pH, contact time and initial ion concentration were analyzed and reported. Adsorption equilibrium data were investigated using Langmuir, Freundlich and Dubinin–Radushkevich isotherm models with three parameters, and the rate of reaction was examined through kinetic models. The results indicate that in particular a novel modified form of red mud, namely iron oxide-coated acid-treated activated red mud was well fitted in lead (II) removal compared with reported adsorbents. The Langmuir isotherm shows that the maximum adsorption of adsorbate per gram was greater than other adsorbents (27.02 mg/g). In Freundlich isotherm, the Freundlich constant n values lie between 1 and 10 indicate the favorable adsorption. The calculated n values for normal red mud, acid-treated activated red mud and iron oxide-coated acid-treated activated red mud were found to be 1.9, 2.1 and 2.0 respectively. The correlation coefficient value was higher and the rate of reaction follows the pseudo-second-order kinetic model.     

Chromium(VI) adsorption from aqueous solution by prepared biochar from <Emphasis Type="Italic">Onopordom Heteracanthom</Emphasis>

In this research, the stems of Onopordom Heteracanthom which is a kind of weed were converted to biochar particles, and their characteristics were investigated. The morphology and purity of these particles were examined by SEM and EDX techniques, respectively. Specific surface area was obtained as 5.73 m² g^?1 by BET method. The biochar particles obtained from Onopordom Heteracanthom were evaluated as an adsorbent to remove Cr(VI) from aqueous environments. The effect of some parameters such as initial concentration of Cr(VI), dosage of adsorbent, and pH were investigated on the adsorption capacity of Cr(VI) onto the adsorbent. The equilibrium data were analyzed by various isotherm models. The results revealed that in this process, the adsorption isotherm and kinetics have more conformity with Langmuir isotherm and pseudo-second-order kinetics, respectively. The multi-linearity of the Weber and Morris adsorption kinetic model indicates that the intra-particle diffusion is not merely the rate-controlling step for the whole adsorption process.     

Biosorption of hexavalent chromium from aqueous solution onto pomegranate seeds: kinetic modeling studies

Hexavalent chromium has been proved to be the reason of several health hazards. This study aimed at evaluating the application of pomegranate seeds powder for chromium adsorption (VI) from aqueous solution. Chromium adsorption percentage (VI) increased with increasing the adsorbent dosage. Chromium adsorption capacity (VI), at pH = 2 and 10 mg/L initial metal concentration, decreased from 3.313 to 1.6 mg/g through increasing dosage of adsorbent from 0.2 to 0.6 g/100 ml. The adsorption rate increased through increase in chromium initial concentration (VI). However, there was a removal percentage reduction of chromium (VI). Chromium adsorption kinetics by different models (pseudo-first-order, modified pseudo-first-order, pseudo-second-order, Elovich, intraparticle diffusion, Boyd kinetic) was investigated as well. Studies on adsorption kinetic indicated that the experimental data were matched by pseudo-second-order model (R ² = 0.999) better. Obtained results demonstrated the pomegranate seeds can be used as an effective biomaterial and biosorbent for hexavalent chromium adsorption from aqueous solutions.     

Investigating the removal of ethylbenzene from aqueous solutions using modified graphene oxide: application of response surface methodology

This research focused on the application of response surface methodology (RSM) for the removal of ethylbenzene by the graphene oxide grafted with polymethyl vinyl ketone and aniline (GO-MVK-ANI) from wastewater. The adsorbent was prepared through polymerization of graphene oxide with methyl vinyl ketone using ammonium persulfate initiator and further modification by aniline. The synthesized material was characterized via Fourier transform infrared resonance spectroscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy and Brunauer–Emmett–Teller analysis. RSM was used to minimize the number of experiments and investigate the effect of three selected parameters (contact time, initial pH and adsorbent dose) on the removal efficiency of ethylbenzene. Additionally, the affecting parameters were optimized based on the selected target (ethylbenzene removal efficiency). The results show that 73% ethylbenzene could be adsorbed with initial ethylbenzene concentration of 20 mg/l under the optimum conditions (the contact time of 11 min, pH of 5.64 and adsorbent dose of 3.75 g/l). In this paper, high R ²-value (97.18%) for ethylbenzene removal and a good agreement with adjusted R ²-value (94.65%) indicated that the model was successful and the results demonstrated a reasonable proportion of the experimental and the predicted results.     

Removal of ibuprofen from aqueous solution by functionalized strong nano-clay composite adsorbent: kinetic and equilibrium isotherm studies

The functionalized nano-clay composite adsorbent was prepared, and its properties were characterized using FT-IR, XRD and SEM techniques. The synthesized nano-clay composite was studied with regard to its capacity to remove ibuprofen under different adsorption conditions such as varying pH levels (5–9), initial ibuprofen concentrations (3, 5 and 10 mg L^?1), contact time, and the amount of adsorbent (0.125, 0.25, 0.5 and 1 g). In order to evaluate the nanocomposite adsorption capacity, the adsorption results were assessed using nine isotherm models. The results showed that the optimum adsorption pH was 6 and that an increase or decrease in the pH reduced the adsorption capacity. The adsorption process was fast and reached equilibrium after 120 min. The maximum efficacy of ibuprofen removal was approximately 95.2%, with 1 g of adsorbent, 10 mg L^?1 initial concentration of ibuprofen, 120 min contact time and pH = 6. The optimal adsorption isotherm models were the Freundlich, Fritz–Schlunder, Redlich–Peterson, Radke–Prausnitz, Sip, Toth and Khan models. In addition, four adsorption kinetic models were employed for adsorption system evaluation under a variety of experimental conditions. The kinetic data illustrated that the process is very fast, and the reaction followed the Elovich kinetic model. Therefore, this nano-clay composite can be used as an effective adsorbent for the removal of ibuprofen from aqueous solutions, such as water and wastewater.     

Lanthanides removal from mine water using banana peels nanosorbent

This study focuses on the performance of nanostructured banana peels in lanthanide-laden mine water treatment. Specifically, nanostructure formation via mechanical milling, characterization in detail and application of this sorbent media in rare earth elements (REEs) removal from synthetic and real mine water are thoroughly investigated. The sorbent samples were characterized by transmission electron microscopy, Brunauer–Emmett–Teller, X-ray diffraction and Fourier transform infrared analyses, while the amount of REEs adsorbed was analysed using inductively coupled plasma optical emission spectroscopy. Results revealed that the particle and crystallite sizes were reduced from <65,000 to <25 nm and 108 to 12 nm, respectively, as the milling progressed. Furthermore, the fracture of particles resulted in a surface area increment from 1.07 to 4.55 m² g^?1. Through Fourier transform infrared analysis, the functional groups responsible for the coordination and removal of metal ions were found to be carboxylic group (at absorption bands of 1730 cm^?1) and amine groups (889 cm^?1). The Langmuir maximum adsorption capacity was 47.8 mg g^?1 for lanthanum and 52.6 mg g^?1 for gadolinium. Meanwhile, results revealed that banana peels have a high affinity for Sm, Eu, Nd, Pr, Gd, Tb and Lu compared to other lanthanides present in the mine water samples. The results obtained so far indicate that nanostructured banana peel is a potential adsorbent for REEs removal from mine water. However, for any application, the water matrix to be treated substantially influences the choice of the sorbent material.