Effects Of Initial Solution pH Research Articles

Equilibrium, kinetic and thermodynamic studies of uranium biosorption by calcium alginate beads

Calcium alginate beads are potential biosorbent for radionuclides removal as they contain carboxyl groups. However, until now limited information is available concerning the uptake behavior of uranium by this polymer gel, especially when sorption equilibrium, kinetics and thermodynamics are concerned. In present work, batch experiments were carried out to study the equilibrium, kinetics and thermodynamics of uranium sorption by calcium alginate beads. The effects of initial solution pH, sorbent amount, initial uranium concentration and temperature on uranium sorption were also investigated. The determined optimal conditions were: initial solution pH of 3.0, added sorbent amount of 40 mg, and uranium sorption capacity increased with increasing initial uranium concentration and temperature. Equilibrium data obtained under different temperatures were fitted better with Langmuir model than Freundlich model, uranium sorption was dominated by a monolayer way. The kinetic data can be well depicted by the pseudo-second-order kinetic model. The activation energy derived from Arrhenius equation was 30.0 kJ/mol and the sorption process had a chemical nature. Thermodynamic constants such as ΔH0, ΔS0 and ΔG0 were also evaluated, results of thermodynamic study showed that the sorption process was endothermic and spontaneous.

Adsorption of In<sup>3+</sup> from Aqueous Solutions by Persimmon Tannins-Immobilized Collagen Fiber

In the present work, a novel adsorbent to effectively adsorbed In3+ from an aqueous solution has been prepared by immobilizing persimmon tannin (PT) on collagen fiber. The adsorption capacities of In3+ on the immobilized PT were evaluated under various treatment conditions including the initial solution pH, solid-liquid ratio and temperature. The results showed that the effect of initial solution pH and solid-liquid ratio on the adsorption capacity were remarkable, while the influence of temperature was insignificant. The adsorption capacity reached 420 mg/g at 303 K and pH 5.0 when the initial concentration of In3+ was 100 mg/L and solid-liquid ratio was 0.2. The adsorption isothermal and kinetic data fitted best to the Freundlich model and the pseudo-second-order model, respectively.All these results indicated that adsorbent adsorbed efficiently and could be used as a low-cost alternative for the adsorption of In3+ in wastewater treatment.

Adsorption of Ag+by persimmon tannins immobilized on collagen fiber

In the present work, a novel adsorbent to effectively adsorb Ag+ from an aqueous solution has been prepared by immobilizing persimmon tannin (PT) on collagen fiber. The adsorption capacity of Ag+ on the immobilized PT were evaluated under various treatment conditions, including the initial solution pH, solid–liquid ratio, temperature, and initial concentration of Ag+. The results showed that the effect of initial solution pH, solid–liquid ratio, and initial concentration of Ag+ on the adsorption capacity were remarkable, while the influence of temperature was insignificant. The adsorption capacity reached 1947 mg/g at 303 K and pH 7.0 when the initial concentration of Ag+ was 800 mg/L and solid–liquid ratio was 0.4. Adsorption equilibrium isotherms of Ag+ on the surface of the adsorbent fibers were studied using Freundlich and Langmuir isotherms. The experimental data fitted best to the Freundlich models. Also, the immobilized PT before and after adsorption of Ag+ was characterized by Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction, and scanning electron microscopy. All these results indicated that the immobilized PT adsorbed efficiently and could be used as a low-cost alternative for the adsorption of Ag+ in wastewater treatment.

Biosorption behaviors of uranium (VI) from aqueous solution by sunflower straw and insights of binding mechanism

Uranium (VI)-containing water has been recognized as a potential longer-term radiological health hazard. In this work, the sorptive potential of sunflower straw for U (VI) from aqueous solution was investigated in detail, including the effect of initial solution pH, adsorbent dosage, temperature, contact time and initial U (VI) concentration. A dose of 2.0 g L−1 of sunflower straw in an initial U (VI) concentration of 20 mg L−1 with an initial pH of 5.0 and a contact time of 10 h resulted in the maximum U (VI) uptake (about 6.96 mg g−1) at 298 K. The isotherm adsorption data was modeled best by the nonlinear Langmuir–Freundlich equation. The equilibrium sorption capacity of sunflower straw was observed to be approximately seven times higher than that of coconut-shell activated carbon as 251.52 and 32.37 mg g−1 under optimal conditions, respectively. The positive enthalpy and negative free energy suggested the endothermic and spontaneous nature of sorption, respectively. The kinetic data conformed successfully to the pseudo-second-order equation. Furthermore, energy dispersive X-ray, fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy demonstrated that U (VI) adsorption onto sunflower straw was predominantly controlled by ion exchange as well as complexation mechanism. The study revealed that sunflower straw could be exploited for uranium remediation of aqueous streams as a promising adsorbent.

Magnetic Graphene Oxide: Effect of Preparation Route on Reactive Black 5 Adsorption.

In this study, the effect of preparation route of magnetic graphene oxide (mGO) on Reactive Black 5 (RB5) adsorption was investigated. The synthesis of mGO was achieved both with (i) impregnation method (mGOi nanoparticles), and (ii) co-precipitation (mGOp nanoparticles). After synthesis, the full characterization with various techniques (SEM, FTIR, XRD, DTA, DTG, VSM) was achieved revealing many possible interactions/forces of dye-composite system. Effects of initial solution pH, effect of temperature, adsorption isotherms and kinetics were investigated in order to conclude about the aforementioned effect of the preparation method on dye adsorption performance of the magnetic nanocomposites. The adsorption evaluation of the magnetic nanoparticles presented higher adsorption capacity of mGOp derivative (188 mg/g) and lower of mGOi (164 mg/g). Equilibrium experiments are also performed studying the effect of contact time (pseudo-first and -second order equations) and temperature (isotherms at 25, 45 and 65 °C fitted to Langmuir and Freundlich model). A full thermodynamic evaluation was carried out, calculating the parameters of enthalpy, free energy and entropy (ΔH0, ΔG0 and ΔS0).

Biosorption of hexavalent chromium from aqueous solution by six brown macroalgae

Abstract The biosorption potential of six brown macroalgae viz. Nizamuddina zanardinii, Stoechospermum marginatum, Cystoseira indica, Dictyota cervicornis, Padina australis, and Sargassum glaucescens, for the removal of hexavalent chromium (Cr(VI)) was investigated in the present study. Optimum conditions were determined by studying the effect of initial solution pH, biomass dosage, initial Cr(VI) concentration, and contact time on Cr(VI) removal by the macroalgae. Cr(VI) sorption was found to be highly pH dependent and maximum sorption was obtained at pH 1.0. Freundlich isotherm model showed the best fit with the equilibrium data. The removal rate of Cr(VI) was relatively rapid during the first 30 min, although the rate decreased gradually and the sorption reached equilibrium in about 70 min for S. marginatum, 90 min for N. zanardinii, and 150 min for D. cervicornis, P. australis, S. glaucescens, and C. indica. Different kinetic models such as pseudo-first-order, pseudo-second-order, and intra-particle d...

Biosorption of Heavy Metal Ions onto Agricultural Residues Buckwheat Hulls Functionalized with 1-Hydroxylethylidenediphosphonic Acid

Novel biosorbent materials obtained from agricultural residues buckwheat hulls (BH) were successfully developed through functionalization with 1-hydroxylethylidenediphosphonic acid (HEDP), and they were characterized. This paper reports the feasibility of using HEDP-BH for removal of heavy metals from stimulated wastewater, the experimental results revealed that the adsorption property of functionalized buckwheat hulls with 120 mesh 120-HEDP-BH for Au(III) was very excellent, and the monolayer maximum adsorption capacity for Au(III) calculated from the Langmuir isotherm models was up to 450.45 mg/g at 35 °C. The combined effect of initial solution pH, 120-HEDP-BH dosage, and initial Au(III) concentration was investigated using response surface methodology (RSM), and the result showed that biomass dosage exerted a stronger influence on Au(III) uptake than those of initial pH and initial Au(III) concentration. Analysis of variance (ANOVA) of the quadratic model demonstrated that the model was highly significant. Moreover, investigation on the adsorption selectivity showed that 120-HEDP-BH displayed strong affinity for gold in aqueous solutions and even exhibited 100% selectivity for Au(III) ions in the presence of Zn(II) and Co(II). Regeneration capacities of 120-HEDP-BH were studied using the eluent solutions of 0.0-5.0% thiourea in 0.1 mmol/L HCl, and it was found that the adsorption capability remains high after several cycles of adsorption-desorption process.

Batch Removal of Crystal Violet from Aqueous Solution by H2SO4 Modified Sugarcane Bagasse: Equilibrium, Kinetic, and Thermodynamic Profile

Batch adsorption studies were carried out using H2SO4 modified sugarcane bagasse (HMSB) for the removal of hazardous Crystal Violet (CV) dye from aqueous solutions. The effects of initial solution pH, adsorbent dose, and temperature on the adsorption process were investigated. The Langmuir isotherm model well described the equilibrium dye uptake while the pseudo-second-order kinetic model showed good agreement with the experimental kinetic data. Gibb's free energy change (ΔG0) was spontaneous for all interactions, and the adsorption process exhibited endothermic enthalpy values. Results suggest that HMSB is an effective adsorbent for the removal of CV from wastewater.

Adsorption behavior of methylene blue dye onto surface modified Strychnos potatorum seeds

Kinetic, mechanism, equilibrium, and thermodynamic behavior of adsorption of methylene blue (MB) dye onto surface modified Strychnos potatorum seeds (SMSP), in an aqueous solution were studied. Batch adsorption experiments were carried out to analyze the effect of initial solution pH, adsorbent dose, contact time, initial MB dye concentration, and temperature on the removal of MB dye. The kinetics of MB dye adsorption onto SMSP follows a pseudo‐second order kinetic model. The adsorption of MB dye onto SMSP was found to be controlled by both surface diffusion and pore diffusion. The diffusivity values were calculated from Boyd kinetic and Shrinking Core Model for varying initial MB dye concentration from 50 to 250 mg L−1. The adsorption equilibrium data were fitted to different adsorption isotherm models such as Langmuir, Freundlich, and Dubinin‐Radushkevich. The equilibrium data fitted best with the Freundlich adsorption isotherm model, which indicates multilayer adsorption of MB dye onto SMSP. The maximum monolayer adsorption capacity estimated with Langmuir isotherm model was 78.84 mg of MB dye molecules per gram of SMSP. Thermodynamic studies showed that the adsorption of MB dye onto SMSP follows an exothermic process. © 2012 American Institute of Chemical Engineers Environ Prog, 32: 624–632, 2013

Synthesis and investigation of TiO2 nanotube arrays prepared by anodization and their photocatalytic activity

TiO2 nanotube arrays were successfully prepared by anodic oxidation method in the electrolyte of ethylene glycol and deionized water mixed in 9:1 volumetric ration including 0.5wt.% NH4F. The microstructure and phase compositions of samples annealing from 0°C to 800°C were characterized by field-emission scanning electron microscope (FESEM) and X-ray diffraction (XRD). FESEM showed that the obtained nanotubes with diameter 80–100nm and length 4.89μm were highly ordered and perpendicular to Ti substrate. The tubular structure collapsed at 680°C. The photocatalytic activity of samples annealing at different temperature were calculated by the degradation of a model dye, methyl orange (MO), under UV light illumination. The results indicated the phase composition and the morphology of TiO2 nanotubes both played an important role in the degradation of MO. In addition, the effects of initial solution pH and dye concentration on degradation of MO had also been investigated. As a result, the optimum values of calcination temperature, initial solution pH and dye concentration were found to be 550°C, 3, 10mg/l, respectively. The best photodegradation of MO was 76% under illumination for 3h.

Equilibrium and kinetics studies of heavy metal ions biosorption on green algae waste biomass

The biosorption of Pb(II), Cd(II), and Co(II), respectively, from aqueous solution on green algae waste biomass was investigated. The green algae waste biomass was obtained from marine green algae after extraction of oil, and was used as low-cost biosorbent. Batch shaking experiments were performed to examine the effects of initial solution pH, contact time and temperature. The equilibrium biosorption data were analyzed using two isotherm models (Langmuir and Freundlich) and two kinetics models (pseudo-first order and pseudo-second order). The results indicate that Langmuir model provide best correlation of experimental data, and the pseudo-second order kinetic equation could best describe the biosorption kinetics of considered heavy metals.

Comprehensive Utilization of Agricultural Bean Husk Powder (CA) Beads – The Research and Application of Using Immobilized Method to Adsorb and Purify Lead of Mine Wastewater

In this study, calcium alginate immobilized bean husk powder(CA) beads was used as an adsorbent for the aim of removing Pb(Ⅱ) ions form the aqueous solutions, and the effect of initial solution pH, contact time, temperature, initial metal ion concentrations and ionic strength in the adsorption process were investigated in detail. Experimental results showed that the amount of adsorbed Pb(Ⅱ) increased with the increasing initial metal ion concentration and solution pH in the examined range. The results showed that the optimum adsorption pH for Pb(Ⅱ) was5.5, the uptake was 10. 78 mg/g, the desorption rates of Pb(Ⅱ) by EDTA was calculated as 90 %. The concentration of Pb(Ⅱ)of mine wastewater reach the first class of irrigation water quality standards after the first time of adsorption treatment, and reach the first class of fishery water quality standard after the second treatment.

Removal of methylene blue from aqueous solutions by straw based adsorbent in a fixed-bed column

In this paper, carboxymethyl straw has been applied to eliminate methylene blue (MB) in a fixed-bed column. The straw based adsorbent has shown high MB uptake in column. Various models such as Thomas, Clark, Adams–Bohart, Yoon–Nelson, Wolborska, and BDST model have been employed to fit the experimental data carefully. Among them, Thomas model is found to be the most suitable one to describe the adsorption behaviors, according with the monolayer chemical adsorption mechanism. Then the effects of initial solution pH, bed height, temperature, initial MB concentration and flow rate on column adsorption have been studied in detail based on Thomas model. It has been found that initial solution pH, bed height, initial MB concentration and flow rate can affect the breakthrough curves obviously, while temperature has no evident influence on the MB adsorption of the modified straw.

Decolorization of anthraquinone dye Reactive Blue 19 by the combination of persulfate and zero-valent iron

Decolorization of anthraquinone dye Reactive Blue 19 (RB19) with sulfate radicals generated in situ from persulfate and zero-valent iron (ZVI) was investigated. The effects of initial solution pH, initial concentration of RB19, ZVI and persulfate, reaction temperature and common dissolved anions were studied. 100% color removal efficiency and 54% TOC removal efficiency were achieved in 45 min with an initial RB19 concentration of 0.1 mM under typical conditions (pH 7.0, 0.8 g L(-1) ZVI, 10 mM persulfate and 30 C). The decolorization efficiency of RB19 increased with higher iron dosage, higher initial persulfate concentration, and higher reaction temperature. It is also an acid driven process. The decolorization process followed pseudo-first order kinetics and the activation energy was 98.1 kJ mol-1. RB19 decolorization was inhibited by common dissolved anions such as CL-, NO3-, H2PO4- and HCO3- since they reacted with sulfate radicals that retarded the oxidation process. The experiment demonstrated that the combination of persulfate and ZVI was a promising technology for the decolorization of dye wastewater.

Adsorption of Bisphenol-A by HDTMA Modified Clinoptilolite

The adsorption of bisphenol-A (BPA) by hexadecyl trimethyl ammonium bromide (HDTMA) modified clinoptilolite was presented. In this paper, the equilibrium adsorption of BPA by HDTMA modified clinoptilolite was described by Freundlich isotherm with a correlation coefficient's square (R2) of 0.988. The kinetics of adsorption was defined by second-order kinetics with a rate constant (Kv) of 1.98 g/mg/h. The absorption rate was fast, and the liquid solid equilibrium was accomplished within 180 minutes. The effects of initial solution pH, and reaction temperatures had been estimated, showing that the adsorption was enhanced gradually by increasing pH value.

Biosorption of Cr(VI) from simulated wastewater using a cationic surfactant modified spent mushroom

A cationic surfactant (dodecyl dimethyl benzyl ammonium bromide) modified spent mushroom (Tricholoma lobayense) was tested as a potential adsorbent for Cr (VI) removal from wastewater. The results showed that surface modification markedly improved the adsorption capacity. The monolayer maximum adsorption capacity calculated from Langmuir isotherm model was up to 43.86mg/g at 25°C, which was comparatively higher than that of most low cost sorbents. In batch studies, the combined effect of initial solution pH, initial Cr (VI) concentration and biomass dosage was investigated using response surface methodology (RSM). It was found that initial pH and adsorbent dosage exerted stronger influence on Cr (VI) removal than that of initial metal concentration. Furthermore, the results of ionic strength and desorption experiments indicated that the reversible electrostatic attraction played an important role in Cr (VI) uptake and the adsorption followed the anionic adsorption mechanism, which was evidenced by X-ray photoelectron spectroscopy (XPS) analysis in the study.

Strontium and calcium ion adsorption by molecularly imprinted hybrid gel

The adsorption of strontium and calcium ions by strontium ion-imprinted hybrid gel derived from bis(trimethoxysilylpropyl)amine (TSPA) was comparatively studied. The effects of initial solution pH, ionic strength, initial metal ion concentration, and temperature on the equilibrium adsorption amount and the separation factor between strontium and calcium ions were comprehensively investigated. In description of the adsorption kinetics, the pseudo second-order model was found to be more suitable than the pseudo first-order model. In general, the equilibrium adsorption amount of both Sr 2+ and Ca 2+ ions was found to increase with the increase in both the initial metal ion concentration and pH, but not to be so sensitive to ionic strength and temperature. The separation of Sr 2+ and Ca 2+ ions could rely on the difference in adsorption kinetics, because Sr 2+ ions were found to adsorb more rapidly than Ca 2+ ions at the early adsorption stage.

Sorption of Al (III) from aqueous solution by fresh macrophyte alligator weed: Equilibrium and kinetics

The removal of Al (III) ions from aqueous solution by locally abundantly low-cost fresh macrophyte, alligator weed, was examined in batch system. Effect of initial solution pH on Al (III) adsorption was investigated and the Al (III) species present in aqueous solution were identified. The main functional groups of the alligator weed were characterized by Fourier transform infrared spectrometer (FT-IR). The equilibrium data fitted to Freundlich and Langmuir isotherms satisfactorily. The pseudo-second-order equation fitted the kinetic data very well. The intraparticle diffusion played an important role in the Al (III) sorption process. Al (III) ions were favorably adsorbed by alligator weed and the values of K f and 1/ n (Freundlich constant) at 25 °C and pH 3.5 were found as 1.9963 (mg/g)/(mg/L) 1/ n and 0.7875, respectively, which are comparable to those of granular activated carbon (2.20 (mg/g)/(mg/L) 1/ n and 0.8695, respectively).

Dynamic studies and pseudo-second order modeling of copper(II) biosorption onto pine cone powder

The chemical interaction between biosorbent functional groups and metal ion species in solution can slightly be altered by chemical treatment of biosorbent surface. The biosorbent kinetics and mechanism for copper(II) biosorption onto pine cone powder and 0.15moldm−3 NaOH treated pine cone powder were determined during batch kinetics with the variation in biosorption temperature and initial copper(II) concentration. Results from this study revealed that surface diffusion of copper(II) is not rate-controlling as observed by the failure of both the pseudo-first and modified pseudo-first order model to discribe the kinetic data. The pseudo-second order model gave a better description of the kinetic data and was able to correlate the model constants with process variables for both samples. Activation energies and thermodynamic parameters of activation obtained from the pseudo-second order model all indicate that the mechanism for copper(II) biosorption on both samples differ. The diffusion partten is complex for the biosorption process, involving pore and film diffusion in the rate determining step and did not follow the same pattern for both samples. Pseudo-isotherms were generated to confirm the fit of the experimental data to the predictions of the pseudo-second order model. It was observed that the generated isotherm data fitted better to the Pseudo-Langmuir-1 isotherm indicating that biosorption was indeed a monolayer coverage of the biosorbent surface confirming the applicability of this model. Effect of initial solution pH and desorption studies confirm the predominance of a slightly different mechanism using both samples.

Biosorption of Cd(II), Ni(II) and Pb(II) from Aqueous Solution by Dried Biomass of Aspergillus niger: Application of Response Surface Methodology to the Optimization of Process Parameters

AbstractIn this study, the biosorption of Cd(II), Ni(II) and Pb(II) on Aspergillus niger in a batch system was investigated, and optimal condition determined by means of central composite design (CCD) under response surface methodology (RSM). Biomass inactivated by heat and pretreated by alkali solution was used in the determination of optimal conditions. The effect of initial solution pH, biomass dose and initial ion concentration on the removal efficiency of metal ions by A. niger was optimized using a design of experiment (DOE) method. Experimental results indicated that the optimal conditions for biosorption were 5.22 g/L, 89.93 mg/L and 6.01 for biomass dose, initial ion concentration and solution pH, respectively. Enhancement of metal biosorption capacity of the dried biomass by pretreatment with sodium hydroxide was observed. Maximal removal efficiencies for Cd(II), Ni(III) and Pb(II) ions of 98, 80 and 99% were achieved, respectively. The biosorption capacity of A. niger biomass obtained for Cd(II), Ni(II) and Pb(II) ions was 2.2, 1.6 and 4.7 mg/g, respectively. According to these observations the fungal biomass of A. niger is a suitable biosorbent for the removal of heavy metals from aqueous solutions. Multiple response optimization was applied to the experimental data to discover the optimal conditions for a set of responses, simultaneously, by using a desirability function.