Removal of Pb(II) and malachite green from aqueous solution by modified cellulose

A low-cost, highly efficient and eco-friendly cellulose-based adsorbent (CMGT) was synthesized and used to uptake Pb(II) and malachite green (MG) from aqueous solutions. The CMGT was characterized by FTIR, SEM, TGA and XRD. Different experimental parameters were evaluated in batch adsorption experiments to determine the optimal adsorption conditions. The optimal pHs for Pb(II) and MG were 5.5 and 7.0, respectively; the optimal contact times for Pb(II) and MG were 60 and 180 min, respectively. Among the Langmuir, Freundlich and Temkin isotherm models, the Langmuir model fitted the adsorption data best for both Pb(II) and MG adsorption. In theory, the maximum adsorption capacities of Pb(II) and MG were 584.80 and 131.93 mg g^?1, respectively. The pseudo-second-order model fitted the experimental data very well, and the thermodynamics were also used to discuss the mechanism in depth. Additionally, desorption tests showed that CMGT could be effectively regenerated by 0.2 mol L^?1 HCl solution and could be reused for at least six cycles successively with a stable sorption ability in the dynamic adsorption process.     

Characterization of radioactive cobalt on graphene oxide by macroscopic and spectroscopic techniques

Graphene oxide (GO) was synthesized using the modified Hummers method and characterized by XRD and FTIR. The sorption of ⁶⁰Co(II) on GO as a function of contact time, pH, polyacrylic acid, ionic strength, temperature and solution concentration was studied by batch technique. The sorption kinetics indicated that the sorption of ⁶⁰Co(II) on GO could be simulated by the pseudo-second-order model very well. The maximum sorption capacities of GO for ⁶⁰Co(II) calculated from Langmuir model at pH 6.40 and T = 300 K was ~62.0 mg/g. The thermodynamic parameters from the temperature-dependent sorption isotherms indicated that the ⁶⁰Co(II) sorption on GO was an endothermic and spontaneous process. The interaction mechanism between GO and Co(II) were outer-sphere surface complexation or ion exchange at pH <7, whereas the inner-sphere surface complexation was observed at pH 7–9 in terms of the analysis of XPS spectra.     

Removal of cadmium(II) and lead(II) ions from model aqueous solutions using sol–gel-derived inorganic oxide adsorbent

A study was conducted concerning the preparation and application of a novel synthetic oxide adsorbent of MgO-SiO₂ type. The material was prepared via a sol–gel route, utilizing magnesium ethoxide and tetraethoxysilane as precursors of magnesium oxide and silica respectively, and ammonia as a catalyst. The powder was comprehensively analyzed with regard to chemical composition (EDS method), crystalline structure, morphology, characteristic functional groups, electrokinetic stability and porous structure parameters (BET and BJH models). The synthesized oxide adsorbent is amorphous, with irregularly shaped particles, a relatively large surface area of 612 m²/g, and negative surface charge over almost the whole pH range. Comprehensive adsorption studies were performed to investigate the adsorption of Cd(II) and Pb(II) ions on the MgO–SiO₂ oxide adsorbent, including evaluation of adsorption kinetics and isotherms, the effect of pH, contact time and mass of adsorbent. It was shown that irrespective of the conditions of the adsorption process, the synthesized MgO–SiO₂ adsorbent exhibits slightly better affinity to lead(II) than to cadmium(II) ions (sorption capacity of 102.02 mg(Pb²⁺)/g and 94.05 mg(Cd²⁺)/g). The optimal time for removal of the analyzed metal ions was 60 min, although adsorption reached equilibrium within 10 min for Pb(II) and within 15 min for Cd(II) ions, which was found to fit well with a type 1 pseudo-second-order kinetic model. Additionally, adsorption efficiency was affected by the pH of the reaction system—better results were obtained for pH ≥7 irrespective of the type of metal ion.     

Impact of environmental conditions on the sorption behavior of Pb(II) onto attapulgite

This paper examined the application of attapulgite as an adsorbent for the removal of Pb(II) from heavy metal-contaminated water under various conditions. The sorption results indicated that the sorption of Pb(II) on attapulgite was strongly dependent on ionic strength at pH < 7.0. Outer-sphere surface complexation or ion exchange may be the main sorption mechanism of Pb(II) on attapulgite at low pH values. No drastic difference of Pb(II) sorption was observed at pH 7.0–10.0, and the sorption at pH > 10.0 was mainly dominated by inner-sphere surface complexation. The sorption of Pb(II) on attapulgite was affected by foreign ions in solution at pH < 7.0, and was not affected by foreign ions at pH > 7.0. The thermodynamic parameters (ΔH°, ΔS° and ΔG°) were evaluated from the temperature-dependent sorption isotherms, and the results indicated that the sorption process of Pb(II) on attapulgite was spontaneous and endothermic in nature.     

Novel graphene oxide/bentonite composite for uranium(VI) adsorption from aqueous solution

A novel graphene oxide/bentonite composite (GO/bentonite) was synthesized and then characterized through powder X-ray diffraction, fourier transform infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy, and energy dispersive spectroscopy. Adsorption achieved equilibrium within 10 min. Moreover, U(VI) adsorption on GO/bentonite was highly dependent on solution pH and independent of ionic strength. These characteristics suggested that inner-sphere surface complexes of U(VI) formed on GO/bentonite. The adsorption of U(VI) from aqueous solution on GO/bentonite was fitted to the pseudo-second-order and Freundlich isotherm models. The maximum sorption capacity of GO/bentonite was 234.19 mg g^?1 under neutral pH at 303 K. GO/bentonite is a potentially powerful adsorbent for the efficient removal of U(VI) from aqueous solutions.     

Kinetic,mechanism and equilibrium studies on removal of Pb(II) using <Emphasis Type="Italic">Citrus limettioides</Emphasis> peel and seed carbon

The sorption behaviour of Pb(II) ions onto activated carbon prepared from Citrus limettioides peel (CLPC) and seed (CLSC), which is a novel waste material, was evaluated as a function of contact time, pH, adsorbent dose, ionic strength, initial metal ion concentration and temperature in batch adsorption processes with raw Citrus limettioides peel (CLP) and seed (CLS). The maximum uptake of lead(II) ions was obtained at pH range 4.0–6.0 for CLPC, CLSC and 5.0–6.0 for raw materials (CLP, CLS). The optimal contact time was found to be 3 h. Surface morphology and functionality of the adsorbent were characterized by scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) analysis and Fourier-transform infrared (FT-IR) spectroscopy. The equilibrium data fit well with the Langmuir isotherm, confirming monolayer coverage of lead(II) ions onto CLP, CLPC, CLS and CLSC. The Langmuir monolayer adsorption capacity of CLP, CLPC, CLS and CLSC was found to be 123.60, 166.67, 15.32 and 142.86 mg/g. The calculated thermodynamic parameters showed that the sorption process was feasible, spontaneous and exothermic in nature. Kinetic studies demonstrated that adsorption of lead(II) ions followed a pseudo-second-order equation, suggesting that the adsorption process is presumably chemisorption. The adsorbents were tested for removal of Pb(II) from electroplating wastewater in connection with the reuse and selectivity of the adsorbents.     

Adsorption of uranium (VI) from aqueous solution by tetraphenylimidodiphosphinate

The adsorption of uranium (VI) using tetraphenylimidodiphosphinate (Htpip) was studied. Factors of affecting sorption efficiency have been investigated and results showed the adsorption of uranium (VI) was equilibrium at pH 4.5, time 20 min, adsorbent dosage 0.005 g and initial concentration 50 mg L^?1 reaching 99.86 mg g^?1 of adsorption capacity and 99.86% of removal efficiency. Additionally, the interfering ions studies showed that the adsorbent possessed excellent adsorption selectivity of uranium (VI). The surface morphology of Htpip was investigated by SEM. The adsorption process of uranium (VI) onto Htpip fit the pseudo-second-order kinetic model and the Freundlich isotherm model very well.     

Sorption of thorium(IV) from aqueous solutions by graphene oxide

Graphene oxide (GO) is one of the most important carbon nano-materials. In this paper, GO was synthesized from flake graphite and characterized by transmission electron microscopy, atomic force microscopy, and X-ray photoelectron spectroscopy. The sorption of Th(IV) on GO was investigated as a function of contact time, solid-to-liquid ratio, pH, ionic strength, and in the presence of fulvic acid (FA) and humic acid (HA) by batch experiments. The sorption percentage of Th(IV) on GO decreased with increasing ionic strength and decreasing solid-to-liquid ratio. The sorption edge of Th(IV) in the presence of FA/HA is much lower than that in the absence of FA/HA. Furthermore, the sorption processes of Th(IV) can be described by a pseudo-second order rate model. Based on the Langmuir model, the maximum sorption capacities (Cs_max) of Th(IV) were about 5.80 × 10^?4 mol/L. From thermodynamic investigation, sorption of Th(IV) on GO is spontaneous and endothermic in nature. The rapid sorption rate and high sorption capacity suggest that GO is a promising adsorbent for Th(IV).     

Synthesis and Th(IV) sorption characteristics of functionalised graphene oxide

A functionalised graphene oxide (FGO) adsorbent was prepared via the γ-radiation-induced grafting of epichlorohydrin (ECH) onto graphene oxide (GO). X-ray photoelectron spectroscopy revealed that ECH was successfully introduced to the GO surface. The grafting yield of ECH increased with an increase of the irradiation dose and with a decrease of the irradiation dose rate. The sorption kinetics of Th(IV) on GO and FGO followed the pseudo-second-order model and the sorption isotherms can be described by the Langmuir model. The maximum sorption capacities of GO and FGO for Th(IV) are approximately 5.80 × 10^?4 and 2.88 × 10^?5 mol/L, respectively. GOs is considered as a kind of materials with high radiation resistance and large sorption capacities, ranking it has high potential industrial applications even under strong radiation environment. In addition, the amount of the oxygen-containing functional groups C=O and O=C–O in FGO decrease with the increase of the irradiation dose, which suggests that C=O and O=C–O contribute more than C–O to the sorption of Th(IV) onto GO and FGO.     

Chemically activated Ipomoea carnea as an adsorbent for the copper sorption from synthetic solutions

An indigenously prepared zinc chloride activated Ipomoea carnea (morning glory), a low-cost and abundant adsorbent, was used for removal of Cu(II) ions from aqueous solutions in a batch adsorption system. The chemical activating agent ZnCl₂ was dissolved in deionised water and then added to the adsorbent in two different ratios 1:1 and 1:0.5 adsorbent to activating agent ratio by weight. Studies were conducted as a function of contact time, initial metal concentration, dose of adsorbent, and pH. Activated Ipomoea carnea (AIC) were characterised using scanning electron microscopy (SEM), iodine number and methylene blue number. High iodine numbers indicates development of micro pores with zinc chloride activation. Maximum adsorption was noted within pH range 6.0(±0.05). Adsorption process is fast initially and reaches equilibrium after about 4 hours. The kinetic data were analysed using pseudo-first-order and pseudo-second-order models. The pseudo-second-order kinetic model was found to agree well with the experimental data. Adsorption equilibrium data were analyzed using Langmuir and Freundlich isotherm models. The Langmuir model represented the sorption process better than the Freundlich model. Based on the Langmuir isotherm, the monolayer adsorption capacity of Cu(II) ions was 7.855 mg?g^?1 for AIC (1:1) and 6.934 mg?g^?1 for AIC (1:0.5).     

Removal of lead from aqueous solutions using Cassia grandis seed gum-graft-poly(methylmethacrylate)

Using persulfate/ascorbic acid redox system, a series of Cassia grandis seed gum-graft-poly(methylmethacrylate) samples were synthesized. The copolymer samples were evaluated for lead(II) removal from the aqueous solutions where the sorption capacities were found proportional to the grafting extent. The conditions for the sorption were optimized using copolymer sample of highest percent grafting. The sorption was found pH and concentration dependent, pH 2.0 being the optimum value. Adsorption of lead by the grafted seed gum followed a pseudo-second-order kinetics with a rate constant of 4.64 x 10(-5) g/mg/min. The equilibrium data followed the Langmuir isotherm model with maximum sorption capacity of 126.58 mg/g. The influence of electrolytes NaCl, Na(2)SO(4) on lead uptake was also studied. Desorption with 2 N HCl could elute 76% of the lead ions from the lead-loaded copolymer. The regeneration experiments revealed that the copolymer could be successfully reused for at least four cycles though there was a successive loss in lead sorption capacity with every cycle. The adsorbent was also evaluated for Pb(II) removal from battery waste-water containing 2166 mg/L Pb(II). From 1000 times diluted waste water, 86.1% Pb(II) could be removed using 0.05 g/20 ml adsorbent dose, while 0.5 g/20 ml adsorbent dose was capable of removing 60.29% Pb from 10 times diluted waste water. Optimum Pb(II) binding under highly acidic conditions indicated that there was a significant contribution of nonelectrostatic interactions in the adsorption process. A possible mechanism for the adsorption has been discussed.     

Adsorption of Pb(II) and Ni(II) From Aqueous Solution by a High-Capacity Industrial Sewage Sludge-Based Adsorbent

In the present study, adsorption of Ni(II) and Pb(II) from aqueous solution was investigated using activated carbon synthesized with industrial wastewater sludge. The synthesized adsorbent was analyzed using nitrogen adsorption–desorption and Fourier transfer infrared (FTIR) techniques. Batch adsorption mode was used to evaluate the effect of solution pH, contact time, adsorbent dose, initial metal ion concentration, and temperature on the adsorption capacity of the synthesized adsorbent. The kinetic data were analyzed using different kinetic models. The pseudo-second-order equation gave the best fit to the experimental data for both metal ions. The equilibrium isotherm data were analyzed using the Langmuir, Freundlich, and Dubinin–Radushkevich (D–R) isotherm models. The results showed that the data obtained for the Ni(II) and Pb(II) adsorption are in good agreement with the Langmuir model. The Langmuir mono-layer maximum adsorption capacities for Ni(II) and Pb(II) ions were estimated to be 74.06 and 88.76 mg g^?1 at 25°C, respectively. In addition, the thermodynamic studies proved that the adsorption process of both metals could be considered endothermic.     

Kinetics and Equilibrium Models for Sorption of Cu(II) onto a Novel Manganese Nano-adsorbent

The studies of kinetics and equilibrium sorption of Cu(II) were undertaken using nanoscale zerovalent manganese (nZVMn) synthesized by chemical reduction in a single pot system. nZVMn was characterized using scanning electron microscopy, energy dispersive x-ray, and surface area determined by Brunauer–Emmett–Teller. The effect of pH, contact time, adsorbent dose, agitation speed, initial Cu(II) concentrations, temperature, and ionic strength on the sorption of Cu(II) onto nZVMn were investigated in a batch system. The kinetic data followed pseudo-second-order. The mechanism was governed by pore diffusion. The equilibrium sorption data were tested by Freundlich, Langmuir, Temkin, Dubinin–Kaganer–Raduskevich, and Halsey isotherm models. The Langmuir monolayer adsorption capacity (Q_max = 181.818 mg/g) is much greater compared to other nano-adsorbents used in sorption of Cu(II). The thermodynamic parameters (ΔH⁰, ΔS⁰, ΔG⁰) revealed a feasible, spontaneous, and endothermic adsorption process. nZVMn has a great potential for effective removal of copper (II) in aqueous solution.     

One-pot synthesis of a novel magnetic activated carbon/clay composite for removal of heavy metals from aqueous solution

Abstract

In the present work, a novel composite consisting of magnetite, activated carbon from spent coffee grounds and natural clay (MACCC) was prepared by a one-pot synthesis method via a simultaneous activation and magnetization processes. Various techniques (XRD, FTIR, SEM, TEM, EDX, BET) were utilized to characterize the synthesized composite before utilizing it as an adsorbent for removal of Cu(II), Ni(II) and Pb(II) ions from aqueous solutions. Conditions for removal of heavy metals were thoroughly optimized as 25?°C, pH of 5.5, adsorbent dosage of 2?g L^?1, and a contact time of 60?min. Three models of pseudo first-, second-order and intraparticle diffusion as well as three models of Langmuir, Freundlich, and Temkin were used to analyze kinetics and isotherms of the adsorption process. Thermodynamics was discussed completely. Regeneration and recyclability of the adsorbent were also evaluated. Based on the analysis of experimental results, a possible adsorption mechanism of heavy metals onto the synthesized composite was proposed. The maximum capacities caculated from Langmuir model followed the order of Pb(II) > Cu(II) > Ni(II) as 143.56, 96.16 and 84.86?mg·g^?1, respectively. The overall results indicated that MACCC is a potential adsorbent for removal of toxic Pb(II), Cu(II) and Ni(II) ions from wastewater due to simple preparation, high removal efficiency and good recyclability.     

Efficient Removal of Cobalt(II) and Strontium(II) Metals from Water using Ethylene Diamine Tetra‐acetic Acid Functionalized Graphene Oxide

Graphene oxide (GO) with high specific surface area was prepared and functionalized with ethylene diamine tetra‐acetic acid (EDTA). The as‐prepared GO and the functionalized one (GO‐EDTA) were characterized using high resolution transmission electron microscopy (HRTEM), Fourier transform infrared spectroscopy (FT‐IR), X‐ray diffraction (XRD), and Raman spectroscopy. The as‐prepared and EDTA funcationalized GO were applied as adsorbent to remove strontium(II) and cobalt(II) from water. The results indicated that the prepared materials are efficient adsorbents for strontium(II) and cobalt(II) removal. The adsorption of Co^II and Sr^II under effects of contact time, temperature, and pH was investigated It is concluded that the maximum adsorption capacities of GO for Co^II and Sr^II were about 168 and 140 mg · g^–1, whereas of GO‐EDTA the values were about 197 and 158 mg · g^–1, respectively. It is indicated that pH 6 and temperature 40 °C are the best condition for Co^II and Sr^II removal from water. The application of Langmuir and Freundlich isotherms indicated that Langmuir isotherm is best fit for Co^II and Sr^II equilibrium adsorption. Adsorption kinetics were studied by applying pseudo first‐order, pseudo second‐order, and intraparticle diffusion models on the experimental data. The results proved that pseudo second‐order model is the best represented adsorption kinetics. Appling the intraparticle diffusion regressions on the experimental data indicated that intraparticle diffusion involved in adsorption process, which was not the only rate‐controlling step.     

Removal of nickel ions by adsorption on nano-bentonite: Equilibrium,kinetics, and thermodynamics

Nano-bentonite was used as an adsorbent to remove nickel ions from aqueous solutions. Experimental investigation was carried out to identify the effect of pH, contact time, initial concentration, and adsorbent dose of Ni(II). Equilibrium data were described by and fitted to Langmuir, Freundlich, and Dubinin–Radushkevich models. Results showed that the optimum conditions for the removal of the Ni(II) are initial concentration 100 mg/L, adsorbent dose 0.5 g, and pH 6. Surface morphology and functionality of nano-bentonite were characterized by SEM and FTIR. The kinetics data were more accurately described by pseudo-second-order model. The intra-particle diffusion model gave multi-linear curves, so more than one step controlled the adsorption process. Nano-bentonite removed nickel with maximum adsorption capacity of 39.06 mg/g (30°C, pH) and thermodynamic data indicated that adsorption reaction is spontaneous and of an endothermic nature.     

Synthesis of Novel Poly[2-(dimethylamino) ethyl methacrylate]/Pumice Stone Hydrogel Composite for the Rapid Adsorption of Humic Acid in Aqueous Solution

In this study, a novel hydrogel composite, poly[2-(dimethylamino) ethyl methacrylate]/pumice (PDMAEMA/Pmc) was designed and its sorption behavior for humic acid (HA) was produced by using batch adsorption techniques. FTIR results showed that pumice was well incorporated with the PDMAEMA matrix. A scanning electron microscopy (SEM) was used in order to determine the morphology of composite hydrogel. In the batch experiments, the adsorption capacity was evaluated depending on different variables such as ionic strength; initial HA concentration; pH and adsorbent dosage. The adsorption capacity was found to be 86.27 mg/g under the optimized conditions. The results revealed that HA adsorption onto PDMAEMA/Pmc was well expressed by the Freundlich isotherm model and the adsorption process was followed by the pseudo second order kinetic model. The reusability tests also indicated that novel PDMAEMA/Pmc adsorbent was an efficient and cost-effective adsorbent for removal of HA.     

Efficient Removal of Pb(II) from Aqueous Medium Using Chemically Modified Silica Monolith

The adsorptive removal of lead (II) from aqueous medium was carried out by chemically modified silica monolith particles. Porous silica monolith particles were prepared by the sol-gel method and their surface modification was carried out using trimethoxy silyl propyl urea (TSPU) to prepare inorganic–organic hybrid adsorbent. The resultant adsorbent was evaluated for the removal of lead (Pb) from aqueous medium. The effect of pH, adsorbent dose, metal ion concentration and adsorption time was determined. It was found that the optimum conditions for adsorption of lead (Pb) were pH 5, adsorbent dose of 0.4 g/L, Pb(II) ions concentration of 500 mg/L and adsorption time of 1 h. The adsorbent chemically modified SM was characterized by scanning electron microscopy (SEM), BET/BJH and thermo gravimetric analysis (TGA). The percent adsorption of Pb(II) onto chemically modified silica monolith particles was 98%. An isotherm study showed that the adsorption data of Pb(II) onto chemically modified SM was fully fitted with the Freundlich and Langmuir isotherm models. It was found from kinetic study that the adsorption of Pb(II) followed a pseudo second-order model. Moreover, thermodynamic study suggests that the adsorption of Pb(II) is spontaneous and exothermic. The adsorption capacity of chemically modified SM for Pb(II) ions was 792 mg/g which is quite high as compared to the traditional adsorbents. The adsorbent chemically modified SM was regenerated, used again three times for the adsorption of Pb(II) ions and it was found that the adsorption capacity of the regenerated adsorbent was only dropped by 7%. Due to high adsorption capacity chemically modified silica monolith particles could be used as an effective adsorbent for the removal of heavy metals from wastewater.     

Investigation of sequestration mechanisms of radionuclide 63Ni(II) on kaolinite in aqueous solutions

To better understand the application of kaolinite as an adsorbent for the decontamination of Ni(II) from radionuclide contaminated aqueous systems, herein, the sorption behavior of radionuclide ⁶³Ni(II) on kaolinite as a function of contacting time, pH, coexistent electrolyte ions, adsorbent concentration, fulvic acid and humic acid was investigated using batch technique. At low pH values, ion exchange and/or outer-sphere surface complexation was the main mechanism of Ni(II) sorption on kaolinite, whereas, the sorption of Ni(II) was dominated by inner-sphere surface complexation at high pH values. The presence of different electrolyte ions can enhance or inhibit the sorption of Ni(II) on kaolinite to some extent. The Langmuir and Freundlich models were used to simulate the sorption isotherms of Ni(II) at three different temperatures of 288, 313 and 338 K. The thermodynamic parameters (i.e., ΔS°, ΔH°, and ΔG°) calculated from the temperature-dependent sorption isotherms indicated that the sorption reaction of Ni(II) on kaolinite was endothermic and spontaneous. The findings in this present study demonstrates that the kaolinite can be used as a cost-effective adsorbent for the solidification and pre-concentration of Ni(II) from large volumes of aqueous systems.     

Chemical modification of rose leaf with polypyrrole for the removal of Pb (II) and Cd (II) from aqueous solution

The rose leaf was successfully modified through coating with polypyrrole (PPy) in chemical oxidative route in order to remove Pb(II) and Cd(II) from aqueous media. The rose leaf/polypyrrole (RL/PPy) composites were characterized in terms of morphology, chemical structure, and conductivity properties. The spectrum were obtained from FTIR results which support the formation of RL/PPy composites. FTIR and SEM results indicate that the polypyrrole is completely covered on rose leaf. The conductivity of composite (1.8215 S/cm) was higher than polypyrrole (2.06 × 10^?3 S/cm). The metal removal studies were monitored by Ultraviolet Visible Absorption Spectrometer (UV-Vis). The optimum conditions were detected for adsorption by changing some experimental conditions (such as adsorbent dosage, contact time and stirring speed, initial concentration of the metal solutions and pH). Following the determination of the optimum conditions, the results of the metal removal from wastewater studies were performed by Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES). Under the optimum conditions, the ICP-OES results obtained for waste water showed the useability of composite for the removal of Pb(II) and Cd(II). The Langmuir and Freundlich models are subjected to adsorption datas. The datas fitted better when by using Freundlich model.