Equilibrium Sorption Data Research Articles

Amine-Functionalized Natural Rubber/Mesostructured Silica Nanocomposites for Adsorptive Removal of Clofibric Acid in Aqueous Phase

This study is the first report on the synthesis, characterization and application of amine-functionalized mesoporous nanocomposites based on natural rubber (NR) and wormhole-like mesostructured silica (WMS). In comparison with amine-functionalized WMS (WMS-NH2), a series of NR/WMS-NH2 composites were synthesized via an in situ sol-gel method in which the organo-amine group was grafted onto the nanocomposite surface via co-condensation with 3-aminopropyltrimethoxysilane (APS) as the amine-functional group precursor. The NR/WMS-NH2 materials had a high specific surface area (115-492 m2 g-1) and total pore volume (0.14-1.34 cm3 g-1) with uniform wormhole-like mesoporous frameworks. The amine concentration of NR/WMS-NH2 (0.43-1.84 mmol g-1) was increased with an increase in the APS concentration, corresponding to high levels of functionalization with the amine groups of 53-84%. The H2O adsorption-desorption measurement revealed that NR/WMS-NH2 possessed higher hydrophobicity than WMS-NH2. The removal of clofibric acid (CFA), a xenobiotic metabolite of the lipid-lowering drug clofibrate, from the aqueous solution using WMS-NH2 and NR/WMS-NH2 materials was investigated using a batch adsorption experiment. The adsorption was a chemical process in which the pseudo-second order kinetic model expressed the sorption kinetic data better than the pseudo first-order and Ritchie-second kinetic order model. In addition, the CFA adsorption sorption equilibrium data of the NR/WMS-NH2 materials were fitted to the Langmuir isotherm model. The NR/WMS-NH2 with 5% amine loading had the highest CFA adsorption capacity (6.29 mg g-1).

Novel 3D carbon fibers derived from Luffa wastes for oil/water separation

In this study, the 3D structure of carbon fibers (CFs) was prepared from Luffa sponge wastes by H3PO4 impregnation with various ratios and a low-temperature carbonization process at 500 °C in a nitrogen atmosphere. The H3PO4-treated Luffa sponge had higher thermal stability and carbonic yield (∼60–70%) than neat-Luffa (∼21%). Characterization analyses exposed that the synthesized CFs derived from H3PO4-treated Luffa exhibited oleophilic and hydrophobic carbonic nature with 3D sponge skeletal, reflecting an ideal structure for oil sorption. The engine oil sorption properties on the CFs were studied by varying the contact time. The engine oil sorption equilibrium data for 3D CFs samples was explained by the pseudo-second-order and intraparticle diffusion models. The equilibrium oil sorption capacities of 3D CFs were as large as 23.1 ± 0.4 g/g for engine oil, 23.7 ± 1.0 g/g for gasoline, 28.1 ± 1.0 g/g for almond oil, and 29.2 ± 0.8 g/g for pomegranate seed oil in 20 min. Moreover, the optimized 3D CFs can be selectively for oil/water separation applications, such as high capacities for various oils, fast kinetic sorption, and reusability (>6 cycles). This research presented a facile and cost-effective process for the 3D CFs through recycling Luffa sponge wastes for rapid oil sorption.

Equilibrium, Thermodynamics, and Regeneration and Reuse of Biosorbents Developed from Pelletized Agricultural Residues for Gas Dehydration

Adsorption process is among the most feasible approaches to gas dehydration in the industry to achieve high-purity products. Developing low-cost and novel bio-based adsorbents from agricultural by-products has recently received growing attention. Canola meal and oat hull with specified compositions have demonstrated a promising potential for the selective removal of water vapor and possess considerable water uptake capacities compared to commercial desiccants. The biosorbents were densified to form pellets of similar size and shape with controlled sorption capacity and physical properties for industrial usage. The current research focuses on sorption equilibrium isotherm and thermodynamics, as well as sorption–desorption and reusability of biosorbent pellets. The experimental water sorption equilibrium data obtained at 25 °C and 101.3 kPa showed a type II isotherm and were successfully modeled by the GAB and Redhead isotherms; however, data obtained at 35 and 45 °C and 101.3 kPa demonstrated a linear isotherm. The water uptake by the biosorbent pellets was exothermic and physisorption, mainly due to the hydrogen bonds formed between water molecules and hydrophilic functional groups on the surface. The pellets were stable over 50 sorption–desorption cycles inside the pressure swing adsorption column without detectable changes in their structure.

PVA-assisted CNCs/SiO2 composite aerogel for efficient sorption of ciprofloxacin.

Efforts to develop a green, inexpensive and effective adsorbent are crucial for eliminating antibiotics in polluted water. The sorption capacity of the as-prepared polyvinyl alcohol (PVA)-assisted cellulose nanocrystals/SiO2 (CNCs/SiO2) composite aerogel to ciprofloxacin (CIP) rises with the increase of temperature and initial concentration. Reverse trend of sorption capacity can be found when increasing the adsorbent dosage of adsorbent. The optimal pH value for the sorption is proved to be 4. It's found in the uniaxial compression test that the maximum load that PVA-assisted aerogels can withstand is nearly 100 times than that of non-PVA aerogels. Sorption results confirm that the Pseudo-second order (R2=0.9885) and Langmuir models (R2=0.9959) fit well to sorption kinetics and equilibrium data, respectively. The rate constant differs from the initial concentration of CIP according to the Pseudo-second order model. The composite aerogel sorption capacity of Langmuir (qmax) for CIP was 163.34mg·g-1. The thermodynamic studies showed that the sorption process is endothermic with the value of enthalpy change of 41.032kJ/mol. Hydrogen bonding, π-π interaction, hydrophobic and electrostatic interactions are the dominant mechanisms of CIP sorption by the PVA-assisted CNCs/SiO2 composite aerogel.

Application of amino-hypophosphite polyampholyte for purification of wastewater containing Ni(ii) ions.

This study investigated the sorption of Ni(ii) ions from an aqueous solution using novel, synthetic amino-hypophosphite polyampholyte resin (AHP) in a batch adsorption system. The removal of Ni(ii) ions was determined as a function of pH (2.0-8.0), initial concentration of Ni(ii) ions (2.0-20.0 mM), resin dosage (1.0-10.0 g dm-3), contact time (0.04-24 h), and temperature (298-318 K). Moreover, continuous fixed-bed column sorption was also studied using model solutions and actual wastewater from the galvanising plant. The batch sorption experimental data showed that the maximum pH for efficient Ni(ii) ion removal was about 5.0. An equilibrium was reached after about 24 hours. The kinetics results were fitted using pseudo-first-order (PFO), pseudo-second-order (PSO), liquid film (LFD), and intraparticle diffusion (IPD) models. Freundlich and Langmuir isotherm models were applied for sorption equilibrium data. The maximum sorption capacity was obtained from the Langmuir equation to be 2.39, 2.52, and 2.62 mmol g-1 at 298, 308, and 318 K, respectively. The thermodynamic parameters for the sorption of Ni(ii) ions on AHP imply the endothermic and spontaneous character of the process. The experimental results demonstrated that amino-hypophosphite polyampholyte resin could be used to effectively remove Ni(ii) ions from model solutions and real wastewater.

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.

Competitive and cooperative adsorption analysis for dye removal from multicomponent system using Prosopis juliflora activated carbon.

In this study, performance evaluation of two adsorbents synthesized using invasive weed, i.e., Prosopis juliflora, was chemically activated using hydrochloric acid (HPJ) and sodium hydroxide (NPJ). The synthesized adsorbents HPJ and NPJ were subjected to SEM, EDX, XRD, FTIR, and porosimetry analysis for characterization and applied for adsorptive removal of rhodamine B (RB) and methyl orange (MO) dyes from monocomponent (MO/RB) and multicomponent (MO + RB) systems in batch mode. Meanwhile, the effect of operational parameters such as contact time, HPJ and NPJ dosage, MO/RB concentration, and [Formula: see text] on sorption of MO/RB dyes was investigated. The adsorption data was modeled through various kinetic and equilibrium models. On the other hand, the multi-dye sorption system was modeled using Langmuir competitive isotherm. Furthermore, the effect of presence of one dye on sorption of other and vice versa, i.e., competitive (antagonistic) and cooperative (synergistic) nature of sorption process, was investigated. From the results, it was observed that pseudo-second-order kinetic and Langmuir isotherm models best fit the adsorption kinetic and equilibrium data for sorption of MO and RB dyes using both HPJ and NPJ as adsorbents. Langmuir's maximum sorption ability (qm) of HPJ for sorption of MO and RB dyes was observed to be 12.77mg/g and 9.95mg/g, respectively, from the monocomponent system. On the other hand, qm of NPJ for sorption of MO and RB dyes was observed to be 10.51mg/g and 8.69mg/g, respectively. Langmuir's sorption ability (qm) was slightly higher in the MO + RB mixture in contrast to MO/RB. As a result, the sorption of MO/RB dyes from the MO + RB system showed synergistic nature. In conclusion, the HPJ and NPJ could be effectively used as sorbents for sorption of dyes from effluents.

Development of Ag-doped on multi-walled carbon nanotubes for the treatment of fish pond effluent

The treatment of fish pond wastewater utilizing nanocomposites by batch adsorption using purified carbon nanotubes and silver-doped carbon nanotubes (CNTs) as nano-adsorbents was explored in this study. Ultraviolet spectroscopy, X-ray diffraction (XRD), and high-resolution transmission electron microscopy (HRTEM) were used to confirm the biosynthesized AgNPs. The metallic silver is associated with the peaks in the XRD pattern, and HRTEM studies indicated that AgNPs are between particle sizes of 11.12 and 15.39 nm. Purified carbon nanotubes (P-CNTs) and silver-doped carbon nanotubes (Ag-CNTs) were produced using a Fe–Ni/kaolin catalyst in a catalytic chemical vapour deposition process, followed by acid purification and doped with silver nanoparticles, respectively. HRTEM, HRSEM, FTIR, and BET were used to characterize the as-synthesized CNTs, P-CNTs, and Ag-CNTs. Both unpurified and purified CNTs were tube-like, extremely porous, and crystalline, with Ag-CNTs having a higher surface area (1068 m2/g) greater than P-CNTs (268.40 m2/g). The batch adsorption process was used to investigate the adsorption behaviour of P-CNTs and Ag-CNTs to remove Fe, Mn, and Zn from fish pond effluent as a function of contact time, adsorbent dosage, and temperature. The Freundlich isotherm described equilibrium sorption data better than the Langmuir isotherm, and the adsorption kinetics fit well with the pseudo-second-order model. A thermodynamic study of the adsorption process found that the change in Gibbs free energy was negative, indicating that the adsorption process was feasible and spontaneous. Consequently, it has been demonstrated that removing heavy metals from aquatic effluent using Ag-doped CNTs is effective in aquaculture.

Synthesis and characterization of hematite biocomposite using cassava starch template for aqueous phase removal of fluoride

In this study, facile synthesis of α-Fe2O3 biocomposite was mediated by cassava starch as a soft template. Batch mode evaluated its sorption behavior for fluoride removal from aqueous media. Characterization studies using analytical techniques confirmed the existence of porous α- Fe2O3 biocomposite with heterogeneous surfaces having a varied affinity for fluoride. The sorption process was optimized using central composite design (CCD) in response surface methodology (RSM) with a good model prediction (R2 = 0.9066). A study of the interaction effect showed the synergy of process variables on fluoride removal with the result's intensity indicated by the nature of contour plot curvature. Based on the RSM optimization, an optimum fluoride removal efficiency of 85.26 % can be achieved at an initial fluoride concentration of 55 mg/L, α- Fe2O3 biocomposite dose of 0.55 g, pH of 7.5, and contact time of 95 min. Sorption equilibrium data were well modeled by Freundlich isotherm (0.9916), indicating multilayer sorption on a heterogeneous surface of the sorbent with a varied affinity for fluoride. Presence of co-existing anions reduced fluoride removal efficiency in the order PO43− > HCO3− > SO42− > NO3− > CƖ− . At the same time, its kinetics was better modeled by pseudo-second-order kinetics (R2 = 0.9764), showing that the sorption process is rate-limiting. The sorption thermodynamics study showed that the process was spontaneous, exothermic, and entropy-driven physisorption. Hence, the results signify that the green synthesized α- Fe2O3 biocomposite could be a potential sorbent for sustainable defluoridation.

Optimization and mechanisms of rapid adsorptive removal of chromium (VI) from wastewater using industrial waste derived nanoparticles

Nowadays, the existence of metal ions in the environment like chromium (VI) is of significant worry because of its high toxicity to many life forms. Therefore, in this study, an inexpensive and eco-friendly nano-adsorbent was produced from the waste of drinking water industry for effective elimination of Cr (VI) from wastewater. The mineralogical and morphological characterization and compositions of the bulk and nano- adsorbents were performed. The adsorption capabilities of nWTRs for Cr(VI) under different experimental conditions of adsorbent dosage, time, Cr (VI) concentration, solution pH, and competitive ions were investigated. The nWTRs adsorbent exhibits very rapid adsorption potential (92%) for Cr (VI) within the first 15 min. Langmuir model showed high predictive capability for describing Cr (VI) sorption equilibrium data. The estimated maximum sorption capacity (qmax) of nWTRs and bWTRs was found to be 40.65 mg g−1 and 2.78 mg g−1 respectively. The sorption kinetics data of Cr (VI) were perfectly fitted to the model of second-order kinetics. High immobilization capability of nWTRs for sorbed Cr (VI) is evident as most of adsorbed Cr (VI) was associated with the residual fraction. The nWTRs efficiency of Cr (VI) removal from wastewater using batch and column techniques were 98.12 and 96.86% respectively. Electrostatic interactions, outer sphere complexation and pore filling are the main mechanisms suggested for binding of Cr(VI) with functional groups of nWTRs. This study demonstrates that the green low-cost nWTRs have the potential to decontaminate industrial wastewater effluents containing Cr (VI).

Sorption and post-sorption performances of Cd, Pb and Zn onto peat, compost and biochar

The development of waste-derived sorbents to immobilize potentially toxic elements (PTEs) is a promising strategy, contributing to the achievement of sustainable development goals (SDGs). Therefore, this study aimed to assess the sorption performance of cadmium (Cd), lead (Pb) and zinc (Zn), comparing sorbents derived from organic fraction of municipal solid waste (composts and biochars) with peat. The physicochemical characterization, equilibrium of sorption, post-sorption analyzes and bioaccessibility were investigated. Results showed that the sorbents have distinct characteristics; however, each material have their particularities favorable to sorption. For instance, peat and composts have the highest cation exchange capacity (800–1100 mmolc kg−1), while biochar produced at 700 °C has the highest specific surface area (91.21 m2 g−1). The sorption equilibrium data revealed the actual sorption capacity and was well explained by the Freundlich and Langmuir isotherms and, in some cases, by the Dubinin-Radushkevich model. Post-sorption analyzes indicated the occurrence of several sorption mechanisms, driven by the physicochemical properties. Electrostatic interaction stood out for peat and compost. The FTIR spectrum for peat proved the complexation with oxygenated functional groups. The composts showed variations in the released cations (e.g. Ca2+ and K+), indicating cation exchange. Differently, for biochars, the XRD patterns showed that precipitation or coprecipitation seems to be one of the main mechanisms, especially for Cd and Pb. Regarding human bioaccessibility, the results of the gastric phase simulation (pH∼1.20) revealed lower percentages of Pb (33–81%) than Cd (91–99%) or Zn (82–99%), especially for the highest concentrations. Nevertheless, in numerical terms, all bioaccessible concentrations inspire care. In conclusion, among the sorbents, composts and biochars presented the best sorption performances and, therefore, have great potential for environmental applications. Furthermore, the bioaccessibility findings indicate that these assays, still little used in experiments with sorbents, are an important tool that should be better explored in the assessment of the environmental risk associated with contamination.

Hydrocarbon Sorption in Flexible MOFs-Part I: Thermodynamic Analysis with the Dubinin-Based Universal Adsorption Theory (D-UAT).

The analysis of empirical sorption equilibrium datasets is still vital to gain insights into material–property relationships as computational methods remain in development, especially for complex materials such as flexible MOFs. Therefore, the Dubinin-based universal adsorption theory (D-UAT) was revisited and evaluated as a simple visualization, analysis, and prediction tool for sorption equilibrium data. Within the theory, gas properties are normalized into corresponding states using the critical temperatures of the respective sorptives. The study shows theoretically and experimentally that the D-UAT is able to condense differences of sorption data visualized in reduced Dubinin plots to just three governing parameters: (a) the accessible pore volume, (b) the reduced enthalpy of sorption, and (c) the framework’s reduced free energy differences (in case of flexible behavior). This makes the theory a fast visualization and analysis tool, the use as a prediction tool depends on rough assumptions, and thus is not recommended.

Effective biosorption of Cu(II) using hybrid biocomposite based on N-maleated chitosan/calcium alginate/titania: Equilibrium sorption, kinetic and thermodynamic studies

In this research work, a hybrid biocomposite based on N-maleated chitosan, amino-thiocarbamate functionalised calcium alginate and anhydrous Titania nanoparticles (NMC-MCA-TiO2) was fabricated. The study involves the one pot facile synthesis of N-maleated chitosan and amino-thiocarbamate functionalised alginate under moderate conditions. Sorbent was conditioned in the form of hydrogel beads and characterized through FT-IR and SEM analysis. Newly grafted functional groups could act as potential chelating sites for enhanced Cu(II) sorption. Modified biopolymers were organo-functionalised which provided excellent support for immobilization of Titania nanoparticles (TiO2) as inorganic filler. Kinetic data illustrated the manifestation of intrinsic chemisorption instead of simple bulk/film diffusion. Equilibrium sorption data fitted well with Freundlich adsorption model (R2 ≈ 0.99) which designated the heterogeneous nature of sorbent. Maximum sorption capacity of biosorbent was found 192 mg/g at 298 K and pH = 6.0. Standard Gibbs free energy change ∆Go (−21.53, −21.97, and − 22.42 kJ/mol), standard enthalpy change ∆Ho (5.12 kJ/mol) and standard entropy change ∆So (0.09 kJ/mol K−1) values suggested that the sorption process to be spontaneous and endothermic. The sorbent 3NMC-MCA-TiO2 could be competitive candidate for economical and rapid adsorptive removal of Cu(II) from dilute contaminated liquids.

Adsorption of Bemacid Red by Poly Tetra (Ethylene Glycol) Dimethacrylate Crosslinked with 2-Hydroxypropyl Methacrylate Hydrogels: Equilibrium and Kinetic Studies

Besides others, textile industries are the primary sources of discharging a massive amount of highly colored wastewater. Adsorption can be considered the most economically favorable technology method for removing dyes from wastewater. This paper reports the synthesis of Poly tetra (ethyleneglycol) dimethacrylate crosslinked with 2-hydroxypropyl methacrylate (Poly (TtEGDMA-cross-2-HPMA)) hydrogelsand its application as a novel sorbent to remove bemacid red (ET2) dye from aqueous solution under various operating conditions. The equilibrium adsorption capacity was found 142.82–883.60 mg ET2 g–1 of 1% TtEGDMA. The adsorbent was characterized using Fourier transform infrared radiation (FTIR) and 13carbon solid-state nuclear magnetic resonance spectra (13C-NMR). The effects of the experimental parameters include dye concentration and crosslinked agent concentration. The kinetic sorption uptake for ET2 by Poly (TtEGDMA-cross-2-HPMA) at various initial dye concentrations was analyzed by pseudo-first and pseudo-second models. Two sorption isotherms, namely the Langmuir and Freundlich isotherms, were applied to the sorption equilibrium data. The sorption kinetics of ET2 onto the hydrogels followed the pseudo-second-order kinetics model (R2 = 0.999) and the adsorption equilibrium data obeyed the Langmuir isotherm model (R2 = 0.999). It can be concluded that Poly (TtEGDMA-cross-2-HPMA) is an alternative economic sorbent to more costly adsorbents used for dye removal in wastewater treatment processes.

Synthesis of hybrid biosorbent based on 1,2-cyclohexylenedinitrilotetraacetic acid modified crosslinked chitosan and organo-functionalized calcium alginate for adsorptive removal of Cu(II)

The present study is based on the synthesis of a novel hybrid biosorbent using 1,2-cyclohexylenedinitrilotetraacetic acid modified crosslinked chitosan and amino-thiocarbamate moiety functionalized sodium alginate (CDTA-CS/TSC-CA). The fabricated sorbent was employed to investigate the efficient recovery of Cu(II) from aqueous media. CDTA-CS/TSC-CA was characterized using Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscopy (SEM). Analysis confirmed the successful modification of both biopolymers and subsequent loading of Cu(II) ions. CDTA-CS/TSC-CA was casted in the form of hydrogel beads having different CDTA-CS to TSC-CA mass ratios i.e., 10.0–40.0% by mass. The hydrogel beads 4CDTA-CS/TSC-CA with CDTA-CS/TSC-CA mass ratio of 40.0% was found most effective for copper sorption. Equilibrium sorption results showed that initial concentration of copper, medium pH, contact time, sorbent dosage and temperature influenced the sorption capacity (qe). Rate of sorption data was interpreted using different kinetic models and found best fitted with pseudo second order rate expression (R2 ≈ 0.99), illustrating that the rate determining step includes the electron density transfer from sorbent coordination sites to central copper ions. Crank's RIDE equation and Elovich chemisorption model (ECM) revealed the presence of two sorption phases, initially rapid sorption followed by comparatively a slow uptake. Equilibrium sorption data was well depicted by Langmuir model and maximum monolayer adsorption capacity (qm) was computed as 276.53 mg·g−1 at 298 K. Standard Gibbs free energy change, ∆G° (−19.99, −20.18 and −20.36 kJ/ mol), standard enthalpy change, ∆H° (−8.95 kJmol) and standard entropy change, ∆S° (0.04 kJ/mol K−1) values suggested that the adsorption process is spontaneous and exothermic. Hence, 4CDTA-CS/TSC-CA was found efficient biosorbent for copper removal from its dilute effluents.

Using nano-magnesium oxide/bentonite composite for cadmium removal from industrial wastewater

Nowadays, the removal of toxic heavy metals from industrial wastewater is a long standing problem due to the industrial progress worldwide. This study mainly focused on the production of a novel nMgO-bentonite nanocomposite using sol–gel method to enhance Cd ions removal from industrial wastewater. The nMgO-bentonite nano-composite was characterized for structural morphology and presence of functional groups using SEM/EDS, XRD and FTIR analysis. Cadmium sorption equilibrium and kinetic data were well fitted to Langmuir and power function models respectively as confirmed by the highest R2 (0.965), and the lowest SE (38*10-6) values among other studied models. The Langmuir removal capacity of the nanocomposite is 200 mg/g which is 60 times greater than that of bentonite. Increased Cd sorption on nano-composite with increased temperature from 287 to 307K and the thermodynamic results revealed that Cd adsorption process was endothermic and spontaneous. The data also showed highly repetitive application of nano-composite during six cycles of adsorption/ desorption experiment. The final results pointed out that nMgO-bentonite nano-composite has great adsorption affinity for Cd and could potentially employ as a cost-effective, ecofriendly and efficient sorbent for Cd removal from contaminated wastewater.

Adsorptive remediation of organic pollutant and arsenic (V) ions from water using Fe3O4-MnO2 nanocomposite

The presence of various pollutants in water poses a threat to human health. In this study, we focused on the removal of organic pollutant methylene blue (MB) and As(V) from the water by using Fe3O4-MnO 2 nanocomposite. The surface area of the as-prepared nanocomposite was found to be 237.39 m2/g. The nanocomposite was further characterized by using analytical techniques like powder XRD, SEM, VSM and transmission electron microscope. The results of the transmission electron microscope (TEM) showed Fe3O4 cores coated by a MnO 2 shell. VSM analysis showed that the Fe3O4-MnO 2 nanocomposite has ferromagnetic behavior. The efficiency of Fe3O4-MnO 2 nanocomposite for the removal of methylene blue (MB) and As(V) from the water was studied by varying the pollutant concentration and contact time. The results showed a maximum adsorption capacity of 146.1 mg/g for MB and 16.6 mg/g for As(V). The sorption equilibrium data fitted to Langmuir adsorption model for both MB and As(V) adsorption. The nanocomposite was magnetically separable and tested for five consecutive adsorption–desorption cycles. The Fe3O4-MnO 2 nanocomposite retained 70% of its adsorption capacity over five consecutive cycles of regeneration for MB as well as As(V). The result obtained suggest that Fe3O4-MnO 2 nanocomposite can be a promising adsorbent for the removal of methylene blue and As(V) present in water.

Modified alginate-chitosan-TiO2 composites for adsorptive removal of Ni(II) ions from aqueous medium

In this study, organo-funtionalization of sodium-alginate has been carried out using phenylsemicarbazide as modifier to graft N, O-donor atoms containing functional groups (amino-carbamate moieties) to offer novel support for TiO2 immobilization. Hybrid composite made of aminocarbamated alginate, carboxymethyl chitosan (CMC) and titanium oxide TiO2 (MCA-TiO2) was prepared for the promising adsorptive remediation of Ni(II). FT-IR, SEM-EDX were employed to characterize MCA-TiO2. The optimization of TiO2 to modified alginate mass ratio was carried out and hydrogel beads with TiO2/MCA mass ratio of 10.0% (2MCA-TiO2) revealed highest sorption efficiency. The produced sorbents were adapted in the form of hydrogel beads for operation. Organic functionalization based on aminocarbamate (OCONHNH2) moieties on linear chains of alginate embedded additional chelating functional sites which enhanced sorption and selectivity. Batch mode experiments were conducted for optimization of pH and sorbent dose. Equilibrium sorption, kinetic and thermodynamic studies were performed to pattern the nature of sorption. Kinetic data was found in close agreement with pseudo-second order rate expression (PSORE). Isothermal equilibrium sorption data was well fitted with Langmuir adsorption model. Maximum sorption capacity was evaluated as 229 mg/g at 298 K and pH = 6.0.

Chitosan capped trimetallic nanoparticles: Synthesis and their Congo red adsorbing activities

Chitosan capped Fe0-based Fe-Pd-Ir (Chi-Fe-Pd-Ir) tri-metallic nanoparticles were fabricated using metal displacement method in presence of sodium borohydride. The preliminary indications of Fe0 production were the appearance of pale yellow color with ferric nitrate, NaBH4, and chitosan. Chitosan was detected by using ninhydrin color test, thermal gravimetric analysis and measurement of relative viscosity. The average molecular weight of chitosan and Chi-Fe-Pd-Ir decreased with increased potassium persulfate concentration. Chi-Fe-Pd-Ir used as an adsorbent for the removal of Congo red. The sorption equilibrium data were fitted into Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich isotherms (DRK). The maximum monolayer adsorption capacity (Q0max), and sorption intensity (n) were estimated to be 93.4 mg/g and 2.0, respectively, from Langmuir and Freundlich adsorption isotherm models. The mean free energy was calculated by using DRK isotherm to be 0.15 kJ/mol. Sorption parameters indicate that the Congo red adsorbed on the surface of Chi-Fe-Pd-Ir through monolayer formation via physisorption process. The adsorption of CR on Chi-Fe-Pd-Ir was in good agreement with the Langmuir adsorption isotherm and pseudo-second-order kinetic model. Protonated amino group of chitosan was also responsible for the adsorption of anionic CR along with the Fe-Pd-Ir NPs.

Enhanced removal of mercury and lead by a novel and efficient surface-functionalized imogolite with nanoscale zero-valent iron material.

A novel hybrid nanomaterial, nanoscale zero-valent iron (nZVI)-grafted imogolite nanotubes (Imo), was synthesized via a fast and straightforward chemical procedure. The as-obtained nanomaterial (Imo-nZVI) was characterized using transmission electron microscopy (TEM), electrophoretic mobility (EM), and vibrating sample magnetometry (VSM). The prepared Imo-nZVI was superparamagnetic at room temperature and could be easily separated by an external magnetic field. Sorption batch experiments were performed for single- and multicomponent systems and demonstrated that Hg2+ and Pb2+ could be quantitatively adsorbed at pH3.0. For multicomponent systems, maximum adsorption capacities of 61.6mg·g-1 and 76.9mg·g-1 were obtained for Hg2+ and Pb2+ respectively. It was observed that the functional groups in Imo-nZVI interact preferentially with analytes according to the Misono softness parameter. The higher performance of Imo-nZVI compared with Imo and nZVI is related to the increased number of adsorption sites in the functionalized nanomaterial. The sorption equilibrium data obeyed the Langmuir model, while kinetic studies demonstrated that the sorption processes of Hg2+ and Pb2+ followed the pseudo-second-order model. This study suggests that the Imo-nZVI composite can be used as a promising sorbent to provide a simple and fast separation method to remove Hg and Pb ions from contaminated water.