Initial Adsorbate Concentration Research Articles

Preparation of amidoxime modified biomass and subsequent investigation of their lead ion adsorption properties

Amidoximated biosorbent (oximated MT) was successfully synthesized from manna tree (Alhagi Graecorum) residue and subsequently applied for the adsorption of aqueous lead ions. The oximated MT was obtained from tri-synthesis steps of dried residue pulverization, polymerization and nitrile amidoximation. The synthesized adsorbent was effectively characterized using Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and energy dispersion x-ray (EDX) measurements. An optimum adsorptive uptake was established at a contact time of 45 min, pH 6.0, and 0.03 g/L adsorbent dosage. The experimental isotherm and kinetic data were best fitted to the Temkin and Elovich models, respectively. Furthermore, the “approaching equilibrium factor” (RE) value of the Elovich model suggests the occurrence of a mildly rising curve, since 0.1 < RE< 0.3. The mechanistic investigation reveals the predominance of pore and intraparticle diffusion mechanism at low (200 mg/L initial adsorbate concentration) and high (400 & 600 mg/L initial adsorbate concentrations), respectively. Furthermore, the thermodynamic study suggests a prevailing endothermic process.

Coupled adsorption-catalytic reduction of permanganate on Co–Al-layered double hydroxide for dye removal

Permanganate (MnO4−) ions were catalytically reduced to MnO2 by water molecules after adsorption on the surface of carbonate intercalated Co–Al-LDH. This reaction was very slow under experimental conditions in the absence of catalyst and was catalyzed by Co–Al-LDH and Co(II) ion had a key role in this process in the pH range of 2.8–13. But, at pH = 14, MnO4− ions reacted with Co(II) ion of adsorbent and produced Co(III). At all pHs, adsorption sites of Co–Al-LDH for MnO4− ions were Co–OH groups. These adsorption sites were located in micropores and mesopores of Co–Al-LDH and were called MI and ME adsorption sites, respectively. MnO4− ions were adsorbed on both adsorption sites in neutral aqueous solutions and only on ME sites at other pHs. Adsorption experiments were carried out at different temperatures, ionic strengths, pHs and initial adsorbate concentrations. Co–Al-LDH acted as a superadsorbent for MnO4− ions and maximum adsorption capacity was 347.9 mg g−1 (2.2 mmol g−1) in neutral aqueous solution at 318 K. The adsorption binding constants and thermodynamic parameters of adsorption of MnO4− ions on Co–Al-LDH were analyzed by ARIAN (adsorption isotherm regional analysis) model. This model determined the boundaries of adsorption of MnO4− ions on Co–Al-LDH under different conditions and showed that this process was endothermic in regions I and II of its isotherms in neutral solution and at pH = 13. This process obeyed ARIAN–Hinshelwood mechanism and water molecules in the pH range of 2.8–13 and hydroxide ions at pH = 14 participated as nucleophile reagents. Reaction in the pH range of 2.8–13 was as follows2MnO4−+ H2O →2MnO2(ad)+32O2+2OH− and at pH = 14 was as2MnO4−+2Co(II)–OH+H2O→2Co(III)–OH+2MnO2ad+32O2+2OH−This adsorbent was used for selective separation of permanganate from cationic safranin O and methylene blue dyes. However, it could not separate anionic methyl orange dye from MnO4− ions.This work further successfully demonstrated an approach to recycle the used Co–Al-LDH using a reducing agent.

Modelling Metribuzin Removal Efficiency Through Adsorption Using Activated Carbon of Olive-waste Cake

A simple mathematical model is developed for the prediction of Metribuzin removal efficiency through adsorption using activated carbon of olive-waste cake for any combination of input conditions. Based on earlier experimental results, factors from three independent variables (pH, initial Metribuzin concentration and adsorbent dose concentration) were incorporated in the model. All the factors are multiplied to derive a combined diminishing factor, which is multiplied with maximum achievable removal efficiency. It is found that although the model results are having good correlation (0.92) with the experimental results, those are slightly away from the ideal line. Through the introduction of an adjustment factor, model predictions are closely matching with the measured values having a correlation coefficient of 0.96. The primary model predicted results are having standard errors as RMSE = 6.34, MAE = 5.99 and RAE = 0.07, whereas the same error statistics of the adjusted model are 1.97, 1.71 and 0.01, respectively. Such modelling technique will predict removal efficiency for any combination of input parameters, which at times are required to be changed for other constraints.

Taguchi’s experimental design for the optimization of the defluoridation process using a novel biosorbent developed from the clamshell waste

Developing new adsorbents from waste containing chitosan materials for defluoridation is gaining vast interest. In the current research, a new adsorbent is developed from Clamshell waste and experimental investigation is done using Taguchi’s statistical design approach with orthogonal array for process variables optimization to obtain the maximum fluoride reduction. Maximum defluoridation efficiency of 87.49% and 26.31 mg/g of sorption capacity was achieved at optimum variable values of pH 7, adsorbate initial concentration 10 mg/L, mixing period 90 min, Clamshell dose 10 g/L, and a temperature 323 K. The percentage contribution of each process variable applying ANOVA is pH 34.24% > adsorbate initial concentration 21.17% > mixing period 18.14% > Clamshell dose 15.33% > temperature 11.12%. The fluoride removal with Clamshell adsorbent followed the Freundlich isotherm and fitted well with the pseudo-second-order kinetic model. Thermodynamic parameters (ΔH = 15.075 kJ/mol, ΔS = 0.132 kJ/mol. K) reveal the sorption mechanism is spontaneous and endothermic. SEM and EDAX are used to study surface morphology and FTIR to know the functional groups on the adsorbent that participate in fluoride binding. The reusability study indicates that clamshell absorbent can be reused up to 3 regeneration cycles. The practical feasibility of using the Clamshell sorbent for fluoride removal from field water samples was found to be quite effective.

Facile synthesis and characterization of folic acid-modified silica nanoparticles and its exploration for adsorptive removal of aluminum(III) from aqueous media

In the current study, folic acid-modified silica nanoparticles (FA-SNPs) were fabricated and used for the removal of Al(III) from aqueous media via solid-phase extraction (SPE) procedure before its spectrometric determination using flame atomic absorption spectrometry (FAAS). The prepared adsorbent was characterized by elemental analysis, infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray powder diffraction (XRD), Brunauer-Emmett-Teller (BET) surface area measurement, and pH at a point of zero charge (pHpzc). Thermogravimetric analysis (TGA) was used to prove the thermal stability of the prepared adsorbent. The influence of several parameters including initial pH, amount of adsorbent, time of contact, initial adsorbate concentration, and the effect of foreign ions was studied. The outcomes presented that optimum adsorption of Al(III) was achieved at pH 3.5, contact time of 30 min, adsorbent dosage of 25 mg, and 25 °C. The experimental data agreed well with the pseudo-2nd order model and was fitted by the Langmuir model with adsorption capacity equal to 17.52 ± 0.122 mg/g. Thermodynamic analysis revealed that the adsorption of Al(III) was spontaneous and exothermic. The procedure was successfully applied for the recovery of Al(III) spiked to some real water samples. The regeneration study using HNO3 indicated the excellent regenerative power of the prepared adsorbent. Moreover, pH-metric titration was used to prove the complexation between Al(III) and the surface of the prepared adsorbent. The obtained results showed that FA-SNPs is an effective, eco-friendly, and low-cost adsorbent that can be used for the removal of Al(III) from aqueous solution.

Sol-gel silica doped with 3-(2-naphthoyl)-1,1-dibutylselenourea, an efficient precursor for removal of Pb(II) and Zn(II) from water samples

ABSTRACT 3-(2-naphthoyl)-1,1-dibutylselenourea was prepared and Sol-gel silica was doped with it. The selenourea organic derivative was characterised in solid state by single-crystal X-ray diffraction, and doped sol-gel materials were characterised by FT-IR and SEM. The doping results were verified from their characteristic prominent bands v(cm−1) = 1753 and 1199 predominantly assigned to C = O and C = Se, respectively. The processed sol-gel was used as adsorbent to investigate its efficiency for removal of M(II) ions from aqueous solution using batch techniques (M = Pb and Zn). The porosity study reveals that the doped sol-gel contains pores which are responsible for the adsorption of metal ions, besides pores present in the material, the ligand possesses active sites (-NH, = O, = Se) readily available for coordination with metal ions, and the material thus acts as efficient chelating agent. Adsorption kinetics, isotherm, effect of equilibration time, initial concentration of adsorbate, and pH on the metal extraction were studied and conditions were optimised. Metal remediation capacity of the hybrid material i.e. sol-gel is pH dependent, and maximum removal was obtained at pH 5 (Pb) and pH 6 (Zn) with in 35 and 15 minutes, respectively. The prepared adsorbent shows rapid equilibrium and enough stability at elevated temperature in the given medium. Desorption of metal ions was carried out in 0.1 M HNO3 solution, and thereafter, sol-gel silica adsorbent was successfully regenerated and reused.

Amine-amide functionalized graphene oxide sheets as bifunctional adsorbent for the removal of polar organic pollutants

Effective mitigation of polar organic impurities from industrial effluents is a global environmental challenge. Here, we describe the solvothermal synthesis of ammonia-functionalized graphene oxide (NH3GO) sheets for adsorptive removal of diverse organic pollutants, such as cationic dye basic blue 41 (BB41), anionic dye methyl orange (MO), and ionic 4-nitrophenol (4-NP), in aqueous media. Structural analysis of NH3GO suggest a potent role of surface acidic and basic binding sites in adsorption of targets through an interplay of dynamic experimental variables, e.g., contact time, pH, initial adsorbate concentration, adsorbent mass, and temperature. At an initial pollutant concentration of 20 mg/L, equilibrium adsorption capacities for BB41, MO, and 4-NP were estimated at 199.5, 64.0, and 54.1 mg/g, respectively, with corresponding partition coefficients of 4156, 79.4, and 14.3 L/g, respectively. Experimental data of all three organic pollutants are best fitted by the pseudo-second-order kinetic model. The adsorption isotherm of BB41 follows a multilayer adsorption pattern, while those of MO and 4-NP fit into a monolayer adsorption pattern. The endothermic and spontaneous nature of the adsorption processes has also been explored for the three targets on NH3GO based on thermodynamic analysis. The prepared NH3GO sheets appear to be a promising adsorbent for the removal of polar organic dyes and aromatics in the solution phase.

Iron/titanium oxide-biochar (Fe2TiO5/BC): A versatile adsorbent/photocatalyst for aqueous Cr(VI), Pb2+, F- and methylene blue

This is the first report of the metal Fe-Ti oxide/biochar (Fe2TiO5/BC) composite for simultaneous removal of aqueous Pb2+, Cr6+, F- and methylene blue (MB). Primary Fe2TiO5 nano particles and aggregates were dispersed on a high surface area Douglas fir BC (∼700 m2/g) by a simple chemical co-precipitation method using FeCl3 and TiO(acac)2 salts treated by base and heated to 80 °C. This was followed by calcination at 500 °C. This method previously was used without BC to make the neat mixed oxide Fe2TiO5, exhibiting a lower energy band gap than TiO2. Adsorption of Cr(VI), Pb(II), fluoride, and MB on Fe2TiO5/BC was studied as a function of pH, equilibrium time, initial adsorbate concentration, and temperature. Adsorption isotherm studies were conducted at 5, 25, and 45 ℃ and kinetics for all four adsorbates followed the pseudo second order model. Maximum Langmuir adsorption capacities for Pb2+, Cr6+, F- and MB at their initial pH values were 141 (pH 2), 200 (pH 5), 36 (pH 6) and 229 (pH 6) mg/g at 45 ℃ and 114, 180, 26 and 210 mg/g at 25 ℃, respectively. MB was removed from the water on Fe2TiO5/BC by synergistic adsorption and photocatalytic degradation at pH 3 and 6 under UV (365 nm) light irradiation. Cr6+, Pb2+, F-, and MB each exhibited excellent removal capacities in the presence of eight different competitive ions in simulated water samples. The removal mechanisms on Fe2TiO5/BC and various competitive ion interactions were proposed. Some iron ion leaching at pH 3 catalyzed Photo-Fenton destruction of MB. Fe2TiO5, BC, and Fe2TiO5/BC bandgaps were studied to help understand photocatalysis of MB and to advance supported metal oxide photodegradation using smaller energy band gaps than the larger bandgap of TiO2 for water treatment. A long range goal is to photocatalytically destroy some sorbates with adsorbents to avoid the need for regeneration steps.

Eco-friendly approach for effective removal for Congo red dye from wastewater using reusable Zn-Al layered double hydroxide anchored on multiwalled carbon nanotubes supported sodium dodecyl sulfonate composites

Herein, high-activityand petal-like Zn-Al layered double hydroxide/multiwalled carbon nanotubes supported sodium dodecyl sulfonate (Zn-Al LDH/SDS/MWCNTs) composites were successfully synthesized as novel, eco-friendly and effective adsorbents. The particularly physical and chemical properties of Zn-Al LDH/SDS/MWCNTs composites were characterized in detail. Besides, the adsorption performance and interaction mechanism of Congo red onto Zn-Al LDH/SDS/MWCNTs were also investigated under various experiment conditions. The initial pH values and adsorbent concentration played significant part in adsorption performance of Congo red dye. The adsorption kinetics and temperature-dependent isotherms of Congo red onto Zn-Al LDH/SDS/MWCNTs were respectively consistent with pseudo second-order model and Langmuir model. The maximum adsorption capacity of Congo red was greatly achieved to 1.42 × 10−3 mol/g adopting Langmuir model, which was much better than those previously reported other composites to date. The experimental results illustrated that the adsorption performance of Congo red onto Zn-Al LDH/SDS/MWCNTs composites was primarily contributed to surface complexation, ion change, π-π interaction, electrostatic interaction together with hydrogen bond to some extent. The experimental results demonstrated that the as-synthesized Zn-Al LDH/SDS/MWCNTs composites are remarkable adsorbents for the wastewater treatment systems. Our study initials a new foresight for understanding the interaction mechanism and preparing highly efficient and eco-friendly adsorbents with excellent adsorption performance for the elimination of organic contaminants.

Optimization, equilibrium, adsorption behaviour of Cu/Zn/Fe LDH and LDHBC composites towards atrazine reclamation in an aqueous environment

Cu–Zn–Fe Layered double hydroxides (LDH) and LDH dispersed on bamboo biochar (LDHBC) was used to study the adsorption of Atrazine by characterizing the adsorption kinetics, isotherms and response surface methodology (RSM) to reveal interactive effects of pH, adsorbent dosage and adsorbate initial concentration towards LDH optimum performance. The estimate of parameters determined for Langmuir isotherm quantities were in the range (21.84–37.91 mg/g) for LDH and (63.64–87.04 mg/g) for LDHBC. Regeneration and reusability after five cycles detected that the adsorption efficiencies of the adsorbents were reduced to 36% for LDH and 66% for LDHBC. Box Behnken design analysis could further reveal optimized conditions for higher Atrazine removal by LDH up to 74.8%. The adsorption mechanisms could be determined by π-π interactions occurring at the interfaces by hydrogen bonding and pore filling effects.

A simple polyacrylamide gel route for the synthesis of MgAl2O4 nanoparticles with different metal sources as an efficient adsorbent: Neural network algorithm simulation, equilibrium, kinetics and thermodynamic studies

• A polyacrylamide gel method have been used to synthesize the MgAl 2 O 4 nanoparticles. • An artificial neural network model of phase purity of MgAl 2 O 4 was constructed. • The microstructure and adsorption performance of MgAl 2 O 4 nanoparticles were compared. • An adsorption mechanism of MgAl 2 O 4 nanoparticles was proposed. The MgAl 2 O 4 nanoparticles with different particle sizes prepared by a polyacrylamide gel method with different metal salts as raw materials which was used to study its efficiency as an adsorbent for removal of Congo red, acid orange 7 and acid fuchsin from wastewater. It was difficult to obtain pure MgAl 2 O 4 nanoparticles with basic magnesium carbonate or aluminum acetate coupled with other metal salts. Based on the molecular weight, coordination number, ion radius and the number of water of crystallization for the metal salt and the phase purity of the target product, a neural network prediction model was established to predict the effect of synthesis parameters on the phase purity of MgAl 2 O 4 . The microstructure characterization confirmed that the minimum particle size of MgAl 2 O 4 nanoparticles prepared with aluminum nitrate and magnesium sulfate as metal salts was about 22 nm, and the maximum particle size of MgAl 2 O 4 nanoparticles prepared with aluminum nitrate and magnesium chloride as metal salts was about 50 nm. Adsorption experiments of MgAl 2 O 4 nanoparticles were performed as a function of process parameters: various dyes including Congo red, acid orange 7 and acid fuchsin, adsorption time, particles size, initial dye concentration, initial adsorbent concentration, pH value and reaction temperature. The thermodynamic studies showed that the adsorption of MgAl 2 O 4 nanoparticles for removal of Congo red from wastewater is an exothermic and spontaneous process. The maximum adsorption capacity of 89.043 mg/g for the MgAl 2 O 4 nanoparticles was found at 1 g/L of initial adsorbent concentration, 100 mg/L of initial dye concentration, 6.9 of pH, and 299.8 K of temperature for removal of Congo red from wastewater. The adsorption of Congo red, acid orange 7 and acid fuchsin can be assigned to the synergistic effect of electrostatic interaction, pore filling and ion exchange. This present work provides a technical reference for the synthesis of other metal oxide nanoparticles using metal salts with different acid groups.

The Use of Gigantochloa Bamboo-Derived Biochar for the Removal of Methylene Blue from Aqueous Solution

In this study, locally grown bamboo ( Gigantochloa spp.) was used as feedstock for pyrolysis production of biochar under various pyrolysis temperatures (400–800°C). The resultant biochars were tested for their performance in adsorptive removal of the methylene blue (MB) dye. The scope of the adsorption experiment includes the effects of adsorbent dosage, solution pH, initial adsorbate concentration, and contact time. The adsorption data confirmed that pyrolysis temperature has a significant effect on adsorptive performance, whereas biochar pyrolysed at 500°C (BC500) has the highest adsorptive performance with the maximum adsorption capacity (derived from the Langmuir model) being 86.6 mg g-1. Basic characterisations (SEM, EDX, XRD, FTIR, and BET) were carried out for BC500 where FTIR and SEM confirmed the adsorption of MB onto the biochar, while the BET data showed the reduction of the BET surface area, total pore volume, and pore diameter after the adsorption process.

Removal of a non-steroidal anti-inflammatory drug (Piroxicam) in an aqueous medium by an agricultural by-product

The presence of pharmaceuticals in the environment has increased. These pollutants are toxic and non-biodegradable. Piroxicam (PRX) is a non-steroidal anti-inflammatory drug that ends up in wastewater via pharmaceutical industry activities and human being consumption. This work aimed to study the pharmaceutical pollutant removal from wastewater using agricultural by-products as low-cost adsorbent material. Different parameters were studied, such as time, initial adsorbate concentrations, and temperature. The study of the initial concentration-effect shows that the greatest amount of adsorbed is observed in low concentrations. The temperature has shown a negative effect in this study. The kinetics show that after 45min, the equilibrium is obtained; that means the exhaustion of all active sites. The representative model of this adsorption is the Langmuir isotherm according to the regression coefficient, which is equal to 0.99. The natural abundance of this material and the low cost of investment could offer a good alternative to other more expensive adsorbents such as activated carbon.

Isotherms studies of equilibrium sorption of Cu2+ unto hydrochloric acid modified shrimp shell waste

Shrimp shell waste contains protein and chitin, which can be converted into chitosan. Chitosan compound was obtained from deacetylation of chitin and can be used as an adsorbent for various heavy metals. In this study, the shrimp processing industry's solid waste containing heads, shells, and tails was mashed and used directly to adsorb Cu 2+ ions. The adsorption process was carried out in batch mode with an adsorbate initial concentration (C 0 ) of 40 ppm. The effects of several process parameters observed were contact time (0 to 180 min), adsorbent dosage (2.5, 5, 7.5, 10 g), and adsorption temperature (30, 40, and 50 °C). The equilibrium time for Cu 2+ ion adsorption using shrimp shell waste powder was attained at 150 min, with a concentration at equilibrium (C e ) of 24.25 ppm. The highest adsorption capacity of 97.81% was obtained at an adsorbent dosage of 10 g and an adsorption temperature of 50 °C. The adsorption isotherm was studied using the Langmuir, Freundlich, Harkins Jura, Temkin, and Dubinin–Radushkevich (DRK) equations. Of the five adsorption isotherms used, the Harkin Jura isotherm model gives the highest R 2 value of 0.9891. Adsorption in this study includes physical adsorption with the heat of adsorption (ΔH) of 7.90 kJ/mol and endothermic adsorption.

Synthesis, antibacterial activity and adsorption studies of Bentonite-iron nanoparticles in the removal of methyl blue dye

Green synthesis of bentonite-iron nanoparticles (Be-FeNPs) has been carried out using the leaf extract of Helicteres isora and its antibacterial and adsorption capacity for the removal of Methyl Blue (MB) dye have been also studied.T he prepared Be-FeNPs and iron nanoparticles (FeNPs) are characterized by UV-visible, FTIR spectroscopic techniques and SEM analysis. The antibacterial activity of Be-FeNPs show good zone of inhibition against E.coli and S.aureus. Further the prepared composite (Be-FeNPs) and bentonite are used as adsorbents for the removal of Methyl Blue (MB) dye in aqueous solution under various experiment parameters like initial concentration, contact time and pH. The optimum initial pH, adsorbent concentration and time were determined to be 8.1, 45°C, and 100 ppm, 80 min for MB adsorption on to Be-FeNPs. The experimental data for MB adsorption fits well to the Freundlich and Langmuir isotherm models. The kinetic equations like Natarajan-Khalaf, Bhattacharya-Venkobachar and Lagergren equations were found to be applicable. The surface morphology of the Be-FeNPs before and after adsorption of dye revealed that it can be used as an excellent adsorbent for dye removal from dilute industrial effluents.

KINETIC AND THERMODYNAMIC STUDIES OF REMOVAL OF 2-NITROPHENOL FROM AQUEOUS SOLUTION USING COWPEA HUSK POWDER TETHERED ON IRON OXIDE.

The uptake of 2-nitrophenol (2NP) from aqueous solution onto cowpea husk powder tethered on iron oxide (CHPI) and pristine cowpea husk powder (CHP) for comparison was investigated under different experimental conditions such as, initial adsorbate concentration, adsorbent dose, contact time, solution pH and temperature using UV-Visible spectrophotometer. Adsorption isotherms were described using the Langmuir and Freundlich models. The experimental data fitted into Freundlich isotherm equation, indicating monolayer adsorption of the adsorbate on the surface of the adsorbent. Kinetic evaluations showed that the adsorption mechanism of the iron tethered cowpea husk powder was well described by the Lagergren pseudo-first-order model with rate constant increasing with initial adsorbate concentration and evaluated to be 9.4x10-3 g·mg−1·min−1 for CHPI and 1.67x10-2 g·mg−1·min−1 for CHP respectively; showing the iron tethered cowpea husk powder as a better adsorbent. The evaluations of enthalpy, entropy and free energy changes revealed that the adsorption processes were spontaneous and endothermic in nature. The study revealed that both adsorbents studied behaved considerably well with an added advantage of convenient adsorbent separation with use of the iron tethered cowpea husk powder.

Adsorption of Copper (II) Ions from Aqueous Solution onto Marble Waste

The presence of heavy metals in the environment is a major concern due to their toxicity for many life forms. This research studied the ability of using Marble Waste (MW) as an adsorbent for the removal of Cu (II) ions from aqueous solution by batch operation. Experimental investigations of a number of operating parameters were performed to assess their effect on the removal of Cu (II) by Marble waste from synthetic solutions. These parameters are contact time, adsorbent dose initial concentration of adsorbate, agitation rate, solution temperature and pH level. The optimum conditions were determined to be pH 6, 2g adsorbent dose, 100 min contact time, 50ppm Cu and 35 0C for copper removal, and particle diameter at 0.275 μm. The adsorption process of copper (II) is tested with Langmuir and Freundlich adsorption isotherm models. The results revealed that copper is considerably adsorbed on Marble Waste and it could be economic method for the removal of copper from aqueous solutions. Moreover this study gives a value added utilization of biomass to remove Cu from wastewater.

Bi-functionalized Ionic Liquid-Thiourea Chitosan for effective decontamination of Cd(II) and Hg(II) from water bodies

Chitosan biopolymer was converted to thiourea-chitosan followed by impregnation with ionic liquid Aliquat-336 using microwave irradiation method. The obtained material Ionic Liquid-Thiourea Chitosan (ILTC) was effectively used for decontamination of Cd(II) and Hg(II) from water bodies. FT-IR, SEM-EDX, XRD and TGA-DTA gives insight of ILTC adsorbent. Choro-complexes of Cd(II) and Hg(II) showed strong adsorption on ILTC as compared native Cd(II) and Hg(II) ions hence the adsorption was carried out in the form of chloro complexes. The adsorption behavior of Cd (II) and Hg (II) ions onto ILTC was investigated through batch method and various batch parameters viz. Contact time, adsorbent dose, initial concentration of adsorbate, pH and point of zero charge were optimized. The maximum adsorption capacities for Cd (II) and Hg (II) at 298 ​K were found to be 442.5 ​mg/g and 203.2 ​mg/g respectively at pH 3.0. Kinetic and thermodynamic parameters of the adsorption process were obtained. The results indicated that adsorption process was spontaneous, exothermic and followed pseudo-second-order kinetics model. Column studies were carried out in order to access the applicability of the material for bulk samples at larger volumes. ILTC could be easily regenerated and efficiently reused.

Studies on biosorbent developed from Rohu fish scales waste for defluoridation of water

ABSTRACT Development of waste-derived biosorbent for fluoride reduction is gaining wider interest to achieve sustainable and cost-effective water treatment. Biosorbent from Rohu fish scales waste produced from the fish market is developed for defluoridation of water. The morphological characteristics of the sorbent surface were analysed by BET, SEM, and EDAX analysis. Sorption experiments were performed in batch mode to estimate the equilibrium, kinetic and thermodynamic parameters. The equilibrium analysis indicates the sorption capacity increases linearly with the concentration of adsorbate ions and follows Freundlich isotherm. Fluoride uptake capacity of 2.972 mg/g with maximum fluoride removal of 92.12% was obtained at optimum values of process parameters: adsorbate initial concentration of 5 mg/L, pH 3, agitation rate of 150 rpm, mixing period of 90 min, temperature 303 K, and dose of 6 g/L. The E value (2.236 kJ/mol) obtained from the DR isotherm suggests the physisorption mechanism for fluoride sorption. The kinetic study indicates that fluoride sorption follows the second-order kinetic model. Thermodynamic parameters ∆H = −14.72 kJ/mol and ∆S = 0.049 kJ/mol which indicates the spontaneous and exothermic sorption nature of adsorption for fluoride reduction using fish scales sorbent. The reuse and regeneration of the exhausted Rohu fish scales sorbent was performed with 0.1 N NaOH to explore the possibility of reuse and found that it could be effectively reused up to six cycles with about 80% regeneration. The study to check practical applicability of defluoridation of field water using Rohu fish scales adsorbent indicates the adsorbent significantly reduced the fluoride.

Facile sol-gel synthesis of calcium oxide nanoparticles for effective removal of Ni(II) from aqueous solution

ABSTRACT In this study, nanoparticles of calcium oxide (CaO-NPs) were prepared via the sol-gel technique and introduced as a highly efficient adsorbent for removing Ni(II) from aqueous media. The prepared adsorbent was characterised via SEM, TEM, FTIR, XRD, and TGA. The pHzpc and surface area were also determined. XRD pattern exposed a polycrystalline nature of the adsorbent. SEM analysis showed that the adsorbent possesses enhanced surface porosity highlighting its potential capacity for adsorption. TEM analysis confirmed the crystallisation of adsorbent with a simple cubic structure. The FTIR spectrum displayed that the adsorbent surface comprises mostly (–OH and C=O) groups which are principally accountable for the adsorption of Ni(II). A series of batch adsorption experiments were done to study the effect of several parameters as pH, adsorbent dose, time of contact, initial concentration of adsorbate, temperature, ionic strength, and presence of interfering ions on the removal of Ni(II) ions from aqueous solutions using CaO-NPs. Maximum removal was obtained with 200 mg of adsorbent after 90 min contact time at pH 7 and 25°C as optimal conditions. The adsorption process was fitted well with Langmuir isotherm model and pseudo-second-order kinetic model, showing that the adsorption of Ni(II) ions on CaO-NPs was monolayer coverage with 166.67 mg/g capacity of adsorption. Thermodynamic studies revealed a spontaneous and endothermic adsorption process. The regeneration study using Na2EDTA indicated that the prepared adsorbent has a high renewal potential without notable loss in its performance. Moreover, the prepared adsorbent proved its good applicability and performance by successful application of the suggested procedure for the recovery of Ni(II) added to some real water samples. Accordingly, the obtained results showed that CaO-NPs can rapidly and efficiently remove Ni(II) from aqueous solutions. Also, CaO-NPs adsorbent is eco-friendly, easy to produce, cost-effective, non-toxic, and with good adsorption-desorption capacity. Therefore, this study will contribute to ecological cleaning and wastewater treatment.