Pseudo-second Order Kinetic Model Research Articles

Removal of COD and color from textile industrial wastewater using wheat straw activated carbon: an application of response surface and artificial neural network modeling.

A novel approach has been undertaken wherein chemically modified wheat straw activated carbon (WSAC) as adsorbent is developed, characterized, and examined for the removal of COD and color from the cotton dyeing industry effluent. Thirty experimental runs are designed for batch reactor study using the central composite method (CCM) for optimizing process parameters, namely biochar dose, time of contact, pH, and temperature, for examining the effect on COD and color-removing efficiency of WSAC. The experimental data have been modeled using the machine learning approaches such as polynomial quadratic regression and artificial neural networks (ANN). The determined optimum conditions are pH: 7.18, time of contact: 85.229min, adsorbent dose: 2.045g/l, and temperature: 40.885°C, at which the COD and color removal efficiency is 90.92 and 94.48%, respectively. The nonlinear pseudo-second order (PSO) kinetic model shows good coefficient of determination (R2 ~ 1) values. The maximum adsorption capacity for COD and color by WSAC is at the pH of 7, the temperature of 40°C, adsorbent dose of 2g/l is obtained at the contact time of 80min is 434.78mg/g and 331.55 PCU/g, respectively. The COD removal and decolorization is more than 70% in the first 20min of the experiment. The primary adsorption mechanism involves hydrogen bonding, electrostatic attraction, n-π interactions, and cation exchange. Finally, the adsorbent is environmentally benign and cost-effective, costing 16.66% less than commercially available carbon. The result of the study indicates that WSAC is a prominent solution for treating textile effluent. The study is beneficial in reducing the pollutants from textile effluents and increasing the reuse of treated effluent in the textile industries.

Preparation of metakaolin-based geopolymer microspheres (MK@GMs) and efficient adsorption of F- from acidic wastewater

Herein, metakaolin-based geopolymer microspheres (MK@GMs: mean size 65.44 μm) are prepared by dispersion-suspension-solidification method. The fabricated MK@GMs is applied for the adsorption of F- from wastewater achieving the optimal adsorption condition of F-: pH = 1, dosage of 0.2 g/100 mL and F- concentration is 30 mg/L. Under the above conditions, the removal rate of F- in water by MK@GMs reach 89.18 % in 1 min, and the drinking water standard (less than1.5 mg/L) set by World Health Organization (WHO) is reached in 20 min. The adsorption kinetics fits the pseudo-second order kinetic model with a faster adsorption rate (k2 = 0.8 g·mg−1·min−1), and adsorption isotherm follows Langmuir model with the maximum adsorption capacity of 202.27 mg/g. According to the competitive adsorption experiment, MK@GMs have high selectivity and follow an order of: PO43- > SO42- > NO3– > Cl-. Meanwhile, MK@GMs still provide excellent removal of F- in real water bodies such as surface water, seawater and tap water. MK@GMs pro and post F- adsorption are analyzed by SEM-EDS, HRTEM, XRD, FT-IR and XPS, which show that aluminum fluoride (AlF3) is formed after adsorption, indicating the adsorption mechanism is mainly chemisorption and ion exchange. In addition, MK@GMs have an excellent immobilization effect on the adsorbed F-. This study is attributed to the facile and environmental-friendly preparation process of MK@GMs, could be deemed as promising application in acidic wastewater on large-scale.

CONJUGATIVE EFFECT OF LOW COST ADSORBENT WITH LACCASE ENZYME FOR REDUCTION OF PULP AND PAPER EFFLUENT LOAD, ITS KINETICS AND THERMODYNAMICS

Pulp and paper industrial effluent has the foremost role in environmental pollution. The key factor of the current study is to determine the conjugative effect of charcoal (60%) and alluvial soil (40%) mixture with laccase enzyme to lessen the effluent load of the pulp and paper industry. The adsorbent mixture of charcoal (60%) and alluvial soil (40%) was used for the adsorption of biological oxygen demand (BOD) chemical oxygen demand (COD), color, and lignin of effluent. The impact of pH, temperature, adsorbent concentration, and adsorption time on the removal procedure were studied. Adsorption equilibrium was achieved after 50 minutes with an agitation rate of 500 rpm at pH 6.0 at 25 degree. Results indicated that COD, BOD, color, and lignin were removed 86%, 80%, 60%, and 62% respectively. Moreover, the laccase enzyme also enhanced the reduction of these parameters as COD 95%, BOD 93% color 83%, and lignin 75%. The experimental batch equilibrium adsorption for COD and BOD was analyzed by Freundlich and Langmuir models and kinetics was also discussed by pseudo-first-order and pseudo-second-order. The BOD and COD data fitted to the pseudo-secondorder kinetic model. Thermodynamics parameters ∆G˚, ∆H˚, and ∆S˚ results indicated thatadsorption was nonspontaneous due to high TDS and lignin, endothermic in nature, and revealed an increase in randomnessand degree of disorderliness at adsorbent mixture during the present study. Consequently, the use of laccase enzyme incombination with an adsorbent mixture presents promising results and is applicable.

Alkaline Modification of Arabica-Coffee and Theobroma-Cocoa Agroindustrial Waste for Effective Removal of Pb(II) from Aqueous Solutions.

Arabica-coffee and Theobroma-cocoa agroindustrial wastes were treated with NaOH and characterized to efficiently remove Pb(II) from the aqueous media. The maximum Pb(II) adsorption capacities, qmax, of Arabica-coffee (WCAM) and Theobroma-cocoa (WCTM) biosorbents (qmax = 303.0 and 223.1 mg·g−1, respectively) were almost twice that of the corresponding untreated wastes and were higher than those of other similar agro-industrial biosorbents reported in the literature. Structural, chemical, and morphological characterization were performed by FT-IR, SEM/EDX, and point of zero charge (pHPZC) measurements. Both the WCAM and WCTM biosorbents showed typical uneven and rough cracked surfaces including the OH, C=O, COH, and C-O-C functional adsorbing groups. The optimal Pb(II) adsorption, reaching a high removal efficiency %R (>90%), occurred at a pH between 4 and 5 with a biosorbent dose of 2 g·L−1. The experimental data for Pb(II) adsorption on WACM and WCTM were well fitted with the Langmuir-isotherm and pseudo-second order kinetic models. These indicated that Pb(II) adsorption is a chemisorption process with the presence of a monolayer mechanism. In addition, the deduced thermodynamic parameters showed the endothermic (ΔH0 > 0), feasible, and spontaneous (ΔG0 < 0) nature of the adsorption processes studied.

Quaternization of Porous Cellulose Beads and Their Use for Removal of Humic Acid from Aqueous Medium

Porous cellulose beads were quaternized with glycidyltrimethylammonium chloride (GTMAC) to explore a potential use of them as an adsorbent for removal of humic acid (HA) from aqueous medium. The introduction of quaternary ammonium groups was confirmed by FT-IR and XPS analysis. The content of introduced quaternary ammonium groups increased with an increase in the GTMAC concentration. The adsorption capacity increased with a decrease in the initial pH value and attained the maximum value at pH 3 and increased with an increase in the content of quaternary ammonium groups. The removal % increased with the dose of quaternized cellulose beads at both pH 3.0 and 6.0. The adsorption process obeyed the pseudo-second order kinetic model and exhibited a better fit to the Langmuir isotherm model, suggesting that the adsorption of HA is accomplished through the electrostatic interaction between a quaternary ammonium group introduced and a dissociated carboxy group of a HA molecule. The maximum adsorption capacity obtained in this study is comparable to or higher than those published by other articles. HA loaded was completely released to NaOH solutions at higher than 100 mM to regenerate the quaternized cellulose beads. The above-mentioned results clearly show that the quaternized cellulose beads prepared in this study can be used as a regenerable adsorbent with high capacity for removal of HA from aqueous medium.

Temperature influence on layered double hydroxide tailored corncob biochar and its application for fluoride removal in aqueous media

Exposure to excess fluoride is a controversial public health concern as it can cause dental/skeletal fluorosis as well as renal toxicity. The study intended to evaluate the synergistic interaction of clay intercalation and thermochemical modification on corncob biochar to remove fluoride from aqueous solutions. Layered double hydroxide was assorted with thermally activated (torrefaction and pyrolysis) corncob biochar at 1:1 (w/w) ratio to obtain composites called LDH-CCBC250 and LDH-CCBC500. Physicochemically characterized adsorbents were assessed against the pH (3–9), reaction time (up to 12 h) and initial fluoride concentration (0.5–10 mg L−1) for defluoridation. The porous structure of biochar was found to be richer compared to biocharcoal. The adsorption performance of LDH-CCBC500 was 6-fold higher compared to LDH-CCBC250 signifying the pronounced effect of thermal activation. Fluoride adsorption was pH dependent, and the best pH was in the range of pH 3.5–5.0 and there was no ionic strength dependency. Fluoride uptake by LDH-CCBC500 follows pseudo-second order and Elovich kinetic models, which suggests a chemisorption process followed by physisorption. The most expected way to eliminate fluoride by LDH-CCBC500, which had a maximum adsorption capacity of 7.24 mg g−1, was cooperative chemical adsorption upon the Langmuir and Hills isotherm (r2 = 0.99) parameters. Layered double hydroxide intercalated corncob biochar derived from slow pyrolysis is best performing in acidic waters.

Pd-ZnO nanoparticles decorated acid activated montmorillonite for the efficient removal of cationic dyes from water

Efficient adsorbent being the need of the hour for the effective removal of dye stuff from textile effluents, we herein report the synthesis of palladium intercalated zinc oxide nanoparticles decorated acid activated montmorillonite (Pd-ZnO@H+-Mt)nanocomposite using ion-exchange process followed by wet impregnation technique with Citrus limon leaf extract as reducing agent and its application as an efficient adsorbent for methylene blue (MB) and malachite green (MG) removal from water. The successful intercalation of Pd into the ZnO lattice was identified by band gap value calculated using UV-DR spectra. ATR FT-IR, XRD, SEM, TEM, TGA, BET, and XPS techniques confirmed the successful preparation of Pd-ZnO@H+-Mt nanocomposite. The synthesized Pd-ZnO@H+-Mt nanocomposite was then evaluated for efficient uptake of cationic dyes through batch adsorption experiments and thereby various parameters that influenced adsorption process were found. The experimental maximum adsorption capacity, qm of Pd-ZnO@H+-Mt for MB and MG dyes were 205 and 167 mg/g. The main driving force for the adsorption of MB and MG was identified to be the presence of mesopores, high specific area of Pd-ZnO@H+-Mt on acid activation, total pore volume and the presence of Pd-ZnO NPs on the surface which enhanced the negative charges of Mt surface thus facilitated better loading of dye molecules. Multilayer coverage of MB/MG molecules on Pd-ZnO@H+-Mt were evidenced through Freundlich isotherm model and experimental data of both MB and MG were described well by pseudo second-order kinetic model. The adsorption phenomenon was identified as feasible, spontaneous, and endothermic for MB adsorption while exothermic for MG adsorption. Moreover, the adsorbent could be recycled thrice. Thus, the synthesized Pd-ZnO@H+-Mt nanocomposite could be utilized effectively in industrial water treatment for the removal of dye stuff as adsorbent.

Synthesis of MIL-100(Fe)@Fe3O4 from Magnetic Zircon Mining Waste Modified by CTAB for Naphthol Dye in Water Removal

The synthesis of MIL-100(Fe)@Fe3O4 composite modified by CTAB has been reported in this study. This research begins with synthesis of magnetite (Fe3O4), using an iron precursor from zircon mining magnetic waste. The MIL-100(Fe)@Fe3O4 was composited with CTAB using a room-temperature in situ synthesis method. The MIL-100(Fe)@Fe3O4-CTAB composite obtained was then characterized using Fourier Transform Infrared spectroscopy and X-ray diffraction. The synthesized MIL-100(Fe)@Fe3O4-CTAB was then used to adsorb naphthol dye from the aqueous phase. The maximum naphthol removal was obtained at a concentration of CTAB of 0.4 M and pH of 6. The adsorption kinetics showed that the adsorption followed a pseudo second-order kinetics model, with the rate constant values for MIL-100(Fe)@Fe3O4-CTAB being 1,712 x 10-2 g/mg.menit, respectively. The results also showed that the adsorption isotherm of MIL-100(Fe)@Fe3O4-CTAB follows the Langmuir isotherm for adsorption capacities of 63,036 mg/g, respectively. The results indicate that naphthol dye can be effectively removed from the aqueous phase by using the iron content in the magnetic waste from zircon mining, which was used as a precursor for the manufacture of MIL-100(Fe)@Fe3O4-CTAB composite.

Porous carbons prepared from a novel hard wood composite waste for effective adsorption of Pb(ii) and Cd(ii) ions.

In our previous investigations, a hard wood composite (HWC) was formulated by adding rice straw, as a filler to the recycled polystyrene foam waste at mass ratio (50/50) at 170 °C and pressed under 40 kPa. Here, the disposed HWC product as a model scrap was applied for production of porous carbons enclosed with graphene sheets. To attain this approach, HWC was hydrothermally carbonized (S1) followed by either post-heat treatment (S2) or potassium hydroxide (KOH, S3) activation at 750 °C for 2 hours. The properties of prepared samples were evaluated using SEM, ATR-IR, and porosity measurements. The adsorption performance of the obtained porous carbons toward removal of lead (Pb(ii)) and cadmium (Cd(ii)) ions from aqueous solutions was investigated under different operating conditions like contact time, initial pH, initial metal ions concentration and adsorbent dose. Kinetic models such as pseudo-first order, pseudo-second order and intraparticle diffusion were used to analyze the adsorption data. Langmuir, Freundlich, Dubinin-Radushkevich and Redlich-Peterson isotherms were applied. Thermodynamics and regeneration studies were performed. The sample (S3) comprised a micro-mesoporous carbon structure encompassed by graphene sheets, with the largest total surface area (422 m2 g-1) and adsorption capacities for Pb(ii) and Cd(ii) ions of 207.9 and 119.6 mg g-1, respectively. The experimental adsorption data were best elucidated using Langmuir and pseudo second-order kinetic models. Thermodynamic experiments confirmed that adsorption is an endothermic and spontaneous process. Conclusively, the investigated HWC waste is a promising carbonaceous precursor for preparing effective porous graphene-carbons used in the removal heavy metals from their aqueous stream.

Synthesis of Mil-100(Fe)@Fe3O4 Composite using Zircon Mining Magnetic Waste as an Adsorbent for Methylene Blue Dye

The objectives of the present study are to synthesize MIL-100(Fe)@Fe3O4 composite and to clarify its ability as an adsorbent for methylene blue dye. The magnetite (Fe3O4) was synthesized using iron precursor from the zircon mining magnetic waste. The MIL-100(Fe) was composited with magnetite using a room-temperature in situ synthesis method. The MIL-100(Fe)@Fe3O4 composite obtained was then characterized using the Fourier transform infrared spectroscopy and X-ray diffraction. The synthesized MIL-100(Fe) and MIL-100(Fe)@Fe3O4 were then used to adsorb methylene blue dye from aqueous phase. The maximum methylene blue removal from both adsorbents was obtained at pH of 9. The adsorption kinetics showed that the adsorption followed a pseudo second-order kinetics model with the rate constant values for MIL-100(Fe) and MIL-100(Fe)@Fe3O4 were 1.012 x 10-2 and 3.963 x 10-2 g/mg.menit, respectively. The results also showed that the adsorption isotherm of MIL-100(Fe) and MIL-100(Fe)@Fe3O4 follows the Langmuir isotherm for adsorption capacities were 137.70 and 151.47 mg/g, respectively. The results indicate that the iron content in the zircon mining magnetic waste as precursor for synthesis MIL-100(Fe)@Fe3O4 composite can be employed as an excellent adsorbent for removal of methylene blue dye from aqueous phase.

Adsorption of Melachite Green onto Activated Carbon Prepared from Clerodendrum serratum

The Clerodendrum serratum leaves obtained from nearby Nagai district, it was used as an adsorbent for the removal of malachite green dye from aqueous solution. The various factors affecting adsorption, such as initial dye concentration, contact time, adsorbent dose and initial pH of solution were evaluated on adsorption of malachite green dye on activated Clerodendrum serratum carbon. The equilibrium adsorption isotherms were analyzed by Langmuir and Freundlich equations. Both Langmuir and Freundlich models can describe the adsorption equilibrium but the Langmuir model shows better agreement. The kinetics of the adsorption process was tested by pseudo-first-order, pseudo-second order, Elovich and Intra-particle diffusion models. It was shown that adsorption of malachite green dye could be described by the pseudo-second order kinetic model. Thermodynamic parameters such as Gibbs free energy (G0 ), the enthalpy (H0 ) and the entropy change of sorption (S0 ) have also been evaluated and it has been found that the adsorption process was spontaneous, feasible and endothermic in nature. The results indicated that activated Clerodendrum serratum carbon can be used as an effective and low-cost adsorbent to remove malachite green dye from aqueous solution.

Lagenaria siceraria Stem Nano Carbon Adsorption Kinetics and Thermodynamics of Malachite Green Dye

Among the most significant industrial pollutants are dyes, notably in the textile industry. Many techniques have been put forth to remove colour from wastewater, but adsorption is the most widely accepted since it can be applied on a broad scale. The Malachite Green dye has been removed from aqueous settings using this work’s application of Modified Activated Lagenaria siceraria Stem Nano Carbon (ALSNC). The effects of pH, contact time, starting concentration, and adsorbent quantity were taken into account. Pseudo-first order, pseudo-second order, and intra-particle diffusion kinetic models were among those utilised to examine the mechanism of the adsorption process. Additionally, equilibrium data was fitted to the Radlich-Peterson isotherm model as well as the Langmuir, Freundlich, and Dubinin-Radushkevich, isotherm models. As a result of raising initial dye concentration, pH, and contact duration, the Malachite Green’s ability to bind to surfaces was improved, according to the results. pH 9 was the ideal level. Malachite Green dye adsorption had a qmax of 15.87 mg/g according to the Langmuir model. The Freundlich isotherm model and the pseudo-second order kinetic model obtained the best fitness when taking into account the values of R2 (0.999) and 2. This work has shown that ALSNC can be used as a cost-effective and efficient adsorbent for the removal of Malachite Green from aquatic environments

Powdered adsorbent obtained from bathurst burr biomass for methylene blue removal from aqueous solutions

Powdered adsorbent obtained from bathurst burr biomass was tested for methylene blue removal from aqueous solutions. SEM and FTIR analyses were used to characterize the adsorbent before and after adsorption. The influence of contact time, adsorbent dose, pH, initial dye concentration, ionic strength and temperature on the process were investigated. Kinetic, equilibrium and thermodynamic studies were conducted to analyse the process. The Taguchi method was used to establish the most suitable conditions for the dye adsorption. The process is spontaneous, favourable, and exothermic and the Freundlich isotherm and pseudo-second order kinetic model best describe it. The Taguchi method indicate that the ionic strength is the factor with the greatest influence on the adsorption process.

The Removal of Dye from Synthetic Wastewater using Hybrid Modified Sugarcane Bagasse-Banana Stem

The potential application of hybrid adsorbents for sugarcane bagasse and banana stem has been explored through the use of a batch adsorption experiment. To ascertain the impact of various dosages and contact times, several experiments were conducted. The Langmuir and Freundlich isotherm models were used to conduct the adsorption analysis. Apart from that, the behaviour and mechanism were analysed utilising the Pseudo-first order and Pseudo-second order kinetic models. The findings reveal that in 100 mL of synthetic dye sample, at an optimal dosage of sugarcane bagasse and banana stem, and at an optimal contact time of 65 minutes, more than 80% of the colour was eliminated. Isotherm models showed that the study was best fitted to Langmuir with a coefficient correlation R2 of 0.9048. In addition, the adsorption kinetics of colour showed that pseudo-second order well-fitted with the coefficient correlation 0.9639, which is bigger than pseudo-first order, 0.4827. Due to the low cost of the media utilised in the study, the hybrid adsorbents of sugarcane bagasse and banana stem have a good potential for colour removal in textile wastewater treatment. As a result, it provides an alternate method of addressing issues associated with an excess of colour in dye wastewater treatment plants.

Copper ions biosorption onto bean shells: Kinetics, equilibrium, and process optimization studies

The removal of copper ions from aqueous solutions using bean shells as an adsorbent is presented in this paper. The influence of the solution pH on the biosorption capacity was investigated. The biosorption capacity increased with the increase in the solution pH. The pseudo-second order kinetic model showed the best agreement with the analysed experimental data, indicating that chemisorption could be a possible way of binding the copper ions to the surface of the bean shells. The Langmuir isotherm model best fitted the analysed isotherm data. The SEM-EDS analysis was performed before and after the biosorption process. The change in the morphology of the sample after the biosorption process was evident, whereby K, Mg, Si and Ca were possibly exchanged with copper ions. Response surface methodology (RSM) based on the Box?Behnken design (BBD) was used to optimize the biosorption process, with the selected factors: the solution pH, initial copper ions concentration and contact time. The optimum biosorption conditions were determined to be: pH 3?4, initial copper ions concentration, 100 mg dm-3, and contact time, 10?30 min.

Porous polyurethane hydrogels incorporated with CMC for eliminating methylene blue from water

ABSTRACT Here, a series of polyurethane porous hydrogels (PUF-s) loaded with different sodium carboxymethyl cellulose (CMC) were successfully prepared by one-step foaming method. The physio-chemical properties and morphologies were characterized. The effects of CMC content, adsorbent dosage, temperature, pH value and other factors on the adsorption of methylene blue (MB) dye in water by CMC-PUF-s were also investigated through static adsorption experiments. The results showed that CMC-PUF-10 had excellent adsorption performance for MB solution with removal rate of 81.47%, and the maximum adsorption capacity was 27.5 mg/g. In addition, the study of adsorption kinetics and adsorption isotherms showed that the adsorption of MB by CMC-PUF was more consistent with Langmuir isotherm adsorption model and pseudo second-order kinetic model. The adsorption thermodynamics study suggested that the adsorption process of MB by CMC-PUF-10 was spontaneous and exothermic at room temperature. The results of cyclic adsorption experiment demonstrated that the removal rate of MB reached above 70% after five cycles, indicating the foams with excellent recyclability. Finally, a low-cost, environmentally friendly and recyclable MB adsorbent was synthesized in this study. As polyurethane foam was synthesized by one-step foaming method, this adsorbent can be prepared on site in practical application and reduce the transportation cost.

Fate and Transport of Lead and Copper in Calcareous Soil

Heavy metals transport to groundwater relies on the characteristics of soil, such as carbonate and clay minerals, organic matter content, soil pH, and some other factors. Most of the heavy metals in calcareous soils are precipitated as metal carbonate minerals; consequently, their transport to the groundwater is not anticipated. Therefore, the current study focused on the impacts of calcium carbonate presence on the adsorption and transport of lead (Pb) and copper (Cu) in calcareous soil using batch and column experiments. To elucidate the contaminants removal mechanisms in calcareous soils, extensive laboratory batch investigations were conducted to study the equilibrium kinetic and adsorption isotherm characteristics of the two studied heavy metals. The quick adsorption of Pb2+ and Cu2+ by soil was seen in kinetics trials. In addition, Pb2+ and Cu2+ sorption onto the soil was best described by the pseudo-second order kinetic model (R2 = 0.9979 and 0.9995 for Cu2+ and Pb2+, respectively). To explain the equilibrium sorption data, the Freundlich isotherm showed the best fitness to Pb2+ (R2 = 0.96) and Cu2+ (R2 = 0.98), collectively. The Freundlich parameters revealed that the Pb2+ has favorable adsorption; however, Cu2+ has unfavorable adsorption onto the soil. The results of column experiments showed the higher binding of Pb2+ than Cu2+ to the top surface of the soil column, making the movement of these two metals very slow. In columns, most of the Pb2+ and Cu2+ ions were sorbed at an initial 5 and 10 cm, respectively. The findings of this study will help in understanding the fate of heavy metals in calcareous soils.

Metal oksit parçacıkları üzerinde kompleks boya molekülünün fraktal adsorpsiyon özellikleri ve istatistiksel analiz yaklaşımı—NiO nanoparçacıkları üzerine Reaktif Siyah 5(RB 5) adsorpsiyonu çalışması

In this study, environmental conditions for high efficient dye adsorption; initial pH, initial dye concentration, temperature, adsorbent concentration were determined as 6.0, 40oC, 100 mgL-1 and 1 g L-1, respectively. Obtained results from SEM, FT-IR and XRD analyzes were evaluated and compared with foundings in literature.&#x0D; It was found that the equilibrium data can be best represented with Langmuir isotherm model, and it was concluded that RB 5-NiO adsorption system behaviour was explained the pseudo-second order kinetic model successfully. It was concluded that dye-nanoadsorbent system was exothermic (ΔH

Characterization and application of ligno-cellulosic fibers derived from Robinia Pseudoacacia for the bio-sorption of methylene blue from water

Ligno-cellulosic biomasses had been recognized for their potential use to produce chemicals and biomaterials. The current study focused on the use of a new cellulosic Robinia Pseudoacacia fiber and extracted lignin as adsorbents for methylene blue (a cationic dye). The biomaterials were analyzed using FT-IR spectroscopy, SEM, XRD, and TGA-DTA techniques. The surface of Robinia fibers was rough and porous. The crystallinity index (CrI) value for Robinia fibers was found to be 32%. The ability of the studied samples to remove methylene blue from water was assessed under the variation of time, pH, dye concentration, temperature, and NaCl concentration. The maximum adsorption capacity of methylene blue reached 191 mg/g for Robinia fibers and it achieved 22 mg/g for the extracted lignin (T = 20 °C, pH = 6, and time = 90 min). The adsorption data complied with the pseudo second-order kinetic model and both Langmuir and Freundlich isotherms. Based on these findings, the process suggested the occurrence of many physicochemical interactions between methylene blue molecules and the studied biomaterials. The adsorption mechanism was exothermic, non-spontaneous, and it was described by the decrease of the disorder. Adsorption results proved that Robinia fiber was an attractive candidate for the removal of cationic dyes from water.

Isotherm, kinetics, thermodynamics and mechanism of metal ions adsorption from electroplating wastewater using treated and functionalized carbon nanotubes

The pollution of the environment emanating from the electroplating wastewater containing cadmium, copper, iron, nickel and lead is a universal critical issue that require efficient treatment methods. Herein, super carbon nanotubes (CNTs) were synthesized on iron-nickel/kaolin catalyst, treated (TR-CNTs) and functionalized (PN@TR-CNTs) as a suitable nanoadsorbent. The nanoadsorbents were characterized to confirm the properties by several physicochemical methods such as x-ray diffraction, Fourier transform infrared spectroscopy, high resolution scanning electron microscopy, high-resolution transmission electron microscopy, energy dispersive x-ray and Brunauer–Emmett–Teller. The characterizations indicate successful synthesis, purification and functionalization of the nanoadsorbents. The surface area of the CNTs, TR-CNTs and PN@TR-CNTs were evaluated as 583.31, 781.88 and 970.81 m2 g−1, respectively. The effect of pH, contact time, nanoadsorbent dosage and temperature on the adsorption of the selected metal ions was carried out and the best conditions were obtained at pH (5 and 6), contact time (60 min), nanoadsorbent dosage (0.4 g/L) and temperature (50 °C). Redlich-Peterson and pseudo second-order isotherm and kinetic models best fitted the experimental data. Similarly, the metal ions adsorption by TR-CNTs and PN@TR-CNTs were thermodynamically spontaneous. The adsorption mechanism was dominated by pore filling and electrostatic attraction, ahead of hydrogen bonding and surface complexation. With good reusability of 6 cycles, the nanoadsorbents can be utilized as a potential material for metal ions removal from electroplating wastewater.