Optimization of Copper and Lead Removal by a Novel Biosorbent: Cucumber (Cucumis Sativus) Peels—Kinetic,Equilibrium, and Desorption Studies

Cucumber peels biosorption efficiency for copper(II) and lead(II) was studied in batch mode. The optimum conditions for removal of Cu(II) and Pb(II) ions were found to be pH 5.0, biosorbent dose of 0.1 g, contact time of 60 and 85 minutes, and initial concentration of 100 and 150 mg/L, respectively. The kinetic data were best described by pseudo-second order model. The biosorption process followed by the Langmuir isotherm model. Maximum monolayer biosorption capacities were 88.50 and 147.06 mg/g for Cu(II) and Pb(II) ions, respectively. Thermodynamic parameters suggest that the biosorption process is spontaneous and endothermic. Desorption studies were carried out with different desorbing agents.     

Evaluation of Pomegranate (Punica Granatum L.) Pulps for the Removal of Copper(II) Ions: Kinetic,Equilibrium, and Desorption Studies

Pomegranate pulp has been used as novel adsorbent for removing Cu(II) ions from aqueous solution. The optimum conditions for removal of Cu(II) ions were found to be pH 5.32, biosorbent dose 0.1 g, contact time 120 minutes, initial concentration 50 mg/L, and temperature 30°C. The kinetic data were well fitted to the pseudo-second-order model. The biosorption process agreed with the Langmuir isotherm model. Maximum monolayer biosorption capacity was 7.30 mg/g. Thermodynamic parameters suggest that the biosorption process is spontaneous and exothermic. Desorption studies were carried out with different desorbing agents.      

Adsorption of Cd(II) Ions onto Activated Carbon Prepared from Hazelnut Husks

In this study, a batch adsorption of Cd(II) ions onto activated carbon (AC) produced from hazelnut husks were investigated. The factors controlling the adsorption process such as initial pH, agitation time, dosage and initial concentration have been examined. The AC was showed a high affinity to Cd(II) ions at pH values between 5.0 and 7.0. The equilibrium time was found to be 300 minutes. Cd(II) adsorption equilibrium was analyzed with both Langmuir and Freundlich isotherm equations and it was found that Langmuir equations fitted well with the experimental data. Maximum Cd(II) adsorption capacity of AC was calculated to be 20.9 mg g^?1. Cd(II) adsorption kinetics described well with the pseudo second order model. The activated carbon prepared from hazelnut husks is efficient sorbent material for the removal of Cd(II) ions from aqueous solutions.     

Comparative Studies of Removal of Methyl Green and Basic Fuchsin from Wastewater by a Novel Magnetic Nanoparticles Mg-Ferrites

Adsorptions of methyl green (MG) and basic fuchsin (BF) by magnetic MgFe₂O₄ were compared in this study. Adsorption mechanism studies indicated that electrostatic interaction may play a main role for MG, but for BF, hydrogen-bond interaction may be more predominant. Kinetics data of both dyes conformed to the pseudo-second order model. The overall rate process was mainly governed by intraparticle diffusion. Comparative isotherm studies indicated that MG followed the Langmuir isotherm and BF followed the Freundlich isotherm. Thermodynamic parameters revealed that the adsorption process was endothermic (ΔH ⁰ > 0) for MG, but it was exothermic (ΔH ⁰ < 0) for BF.     

Influence of Molecular Weight on Mild Steel Corrosion Inhibition Effect by Polyvinyl Alcohol in Hydrochloric Acid Solution

The corrosion inhibition of mild steel in hydrochloric acid solution in the presence of three different molecular weights of polyvinyl alcohol (PVA) designated as PVA-I, PVA-II, and PVA-III corresponding to 14,000, 72,000, and 125,000 g mol^?1, respectively, was investigated using electrochemical impedance spectroscopy, linear polarization resistance (LPR), and potentiodynamic polarization techniques at 25°C. It was found that PVA of different molecular weights inhibited the corrosion of mild steel in the acid environment. Inhibition efficiency (η%) increases with increase in concentration of the polymers. LPR measurements clearly show that inhibition efficiency increases with increasing molecular weight in the order PVA-III > PVA-II > PVA-I. Polarization curves indicate that PVA functions as a mixed inhibitor affecting both the anodic metal dissolution and cathodic hydrogen evolution partial reactions of the corrosion process. The experimental data obtained fitted well into Langmuir adsorption isotherm model. Physical adsorption mechanism is proposed from the thermodynamic (free energy of adsorption) parameters obtained.     

Adsorptive Removal of Thorium(IV) from Aqueous Solutions Using Synthesized Polyamidoxime Chelating Resin: Equilibrium,Kinetic, and Thermodynamic Studies

In this study, an amidoximated chelating ion exchange resin was prepared by poly-acrylonitrile (PAN) grafted potato starch. The adsorbent characterizations such as specific surface area, pore volume, average pore radius, and Fourier transform infrared (FTIR) spectrum of the resin were measured. The effects of pH, adsorbent dosage, contact time, initial concentration of thorium ion, and temperature on adsorption of thorium ion from aqueous solutions were investigated. Four isotherm models including Langmuir, Freundlich, Dubinin-Radushkevich, and Temkin were applied to analyze the equilibrium isotherm data. The results showed that Langmuir and Temkin models had a good agreement with experimental data. The maximum capacity of the adsorbent using the Langmuir isotherm model was 227.27 mg · g^?1. The kinetic models like pseudo-first-order, pseudo-second-order, Elovich, and intraparticle were examined to describe the adsorption process. The kinetics of the adsorption process was found to follow the pseudo-second-order kinetic model. The thermodynamic parameters (ΔG°, ΔH°, ΔS°) were also calculated using equilibrium constant values at various temperatures (25, 35, 45, 55°C) and the positive value for ΔH° showed an endothermic adsorption process. The study suggests that the prepared adsorbent has promising potential for the removal of thorium from wastewaters.      

Flocculation of Bacillus amyloliquefaciens H Disintegrates with Cationized Starch and Aminated Hydroxyethylcellulose

The ability of cationized hydroxyethylated starch (CHES) and aminated hydroxyethylcellulose (DEAE-HEC) to flocculate cell disintegrate of Bacillus amyloliquefaciens H (BamHI) was investigated. The efficiency of flocculation was compared to that of synthetic polymer polyethyleneimine (PEI) and natural polysaccharide chitosan. The influence of salt concentration and biomass concentration on flocculation efficiency was investigated. It was found that the efficiency of flocculation with CHES and DEAE-HEC was similar to that of PEI but better compared to chitosan. Recovery of total soluble proteins at higher than 0.3% concentration of flocculant decreased by more than 18.8% and 42.3% compared to PEI and chitosan, respectively. The yield of BamHI restriction endonuclease activity with all flocculants was similar except for chitosan where 13.1% lower yield was obtained. Meanwhile, efficiency of flocculation with CHES and DEAE-HEC depends drastically on the salt concentration, that is, flocculation diminishes if NaCl concentrations higher than 0.2 M (for CHES) or 0.1 M (for DEAE-HEC) are used. The results have shown that CHES and DEAE-HEC are promising flocculants of cell disintegrates if higher yield of protein is of great concern.     

Pb(II) removal from aqueous solution by polyacrylic acid stabilized zero-valent iron nanoparticles: process optimization using response surface methodology

Optimization and modeling of Pb(II) removal using polyacrylic acid stabilized zero-valent iron nanoparticles (PAA-ZVINs) from aqueous solution was performed. Central composite design (CCD) as the most applicable method in response surface methodology (RSM) was employed for optimization of Pb(II) removal. ZVINs were synthesized using the borohydride reduction method in the presence of PAA as a stabilizer and characterized via scanning electron microscopy (SEM) and X-ray diffraction (XRD). The independent variables for CCD optimization of Pb(II) removal were initial solution pH, ZVINs concentration (g/L), and initial concentration of Pb(II) (mg/L). Results showed a significant correlation between predicted values obtained from second-order polynomial model and experimental values (R ² = 93.19 and adj-R ² = 87.07). Maximum removal of Pb(II) (90.09 %) was observed at the optimal conditions of ZVINs concentration of 3 g/L, initial Pb(II) concentration of 10 mg/L, and initial solution pH of 5.     

Experimental Study and Numerical Modeling of Rheological and Flow Behavior of Xanthan Gum Solutions Using Artificial Neural Network

This study investigated effect of temperature, concentration, and shear rate on rheological properties of xanthan gum aqueous solutions using a Couette viscometer at temperatures between 25°C and 55°C and concentrations of 0.25 wt% to 1.0 wt%. The Herschel–Bulkley model described very well the non-Newtonian behavior of xanthan gum solutions. Shear rate, temperature, and concentration affected apparent viscosity and an equation was proposed for the temperature and concentration effect valid for each shear rate. This article also presents an artificial neural network (ANN) model to predict apparent viscosity. Based on statistical analysis, the ANN method estimated viscosity with high accuracy and low error.     

Adsorption of Cd(II) by Sol-Gel Silica Doped with N-(dipropylcarbamothioyl)thiophene-2-carboxamide

Sol-gel silica was doped with N,N-(dipropylcarbamothioyl) thiophene-2-carboxamide to investigate the sorption of cadmium (Cd) ions from aqueous media. In doped sol-gel silica, the large reagent molecules entrap into pores, whereas, small metal ions diffuse into pores where they make complex with doped reagent. This complexation can be accomplished by either ion exchange or chelation. Doped sol-gel sorbent was applied for removal of Cd(II) from aqueous solution in our study. Adsorption kinetics, adsorption isotherm, equilibration time, effect of initial concentration of adsorbate, and pH effect on the metal removal were studied to optimize the conditions. The prepared adsorbent shows rapid equilibrium and high stability toward high temperature and applied medium. In addition, desorption of metal ions was carried out by 1 M HCl and, thereafter, sol-gel silica adsorbent was regenerated and reused periodically.