Existence of heavy metals like zinc within water source is considered as one of the most important environmental problems. Accumulating within alive tissues, zinc raises various diseases and disorders. Chitosan is a hydrophilic polymer which is raised from acetyl groups of chitin from alkaline solution: it is employed widely as a well-known adsorbent for removing heavy metal ions. Present study aimed at optimizing the production of chitosan nano size particles by method of calvo and compared the adsorption of Zn (II) ions by chitosan macro and nano size particles. Adsorption experiments were conducted in a batch system and the effects of temperature, pH, contact time and initial concentration of metal ions on productivity of adsorption of zinc ions have been considered. Performing analysis DLS revealed that mean size of nano chitosan particles is 19.84 nm. Optimal adsorption by chitosan and nano chitosan has been done in pH 7 and about of 5. Efficiencies of both adsorbent were increased by increasing contact time. Both adsorbent had maximum efficiency at the temperature of 25°C. At the concentration of 10 mg/ L of zinc metal ions, maximum effective removal of chitosan macro and nano size particles were 90.80 and 99.10 %, respectively. Maximum capacity of adsorption by chitosan macro and nano size particle was 196.07 and 370.37 mg/g, respectively. Adsorption kinetics followed a pseudo second order model. Nanochitosan compared to chitosan particles had higher removal efficiency for Zinc metal ions due to nano size of particles, larger adsorption surfaces and more functional groups.
In this paper, a model of simultaneous mass and heat transfer within a porous catalyst in a flat particle is considered. A new modification of the shooting reproducing kernel Hilbert space (SRKHS) method is proposed, which is also capable of handling the system of nonlinear boundary value problems by employing Newtons method. The proposed method is a well-performance technique in both predicting and calculating multiple solutions of the nonlinear boundary value problems. Applying the SRKHS method shows that the mentioned model might admit multiple stationary solutions (unique, dual or triple solutions) depending on the values of the parameters of the model. Furthermore, the convergence of the method is proved and some numerical tests reveal the high efficiency of this new version of SRKHS method.
Electrochemical noise signals in many cases exhibit a DC drift that should be removed prior to further data analysis. Polynomial fitting and moving average removal method have been used to remove trends of electrochemical noise (EN) in time domain. The corrosion inhibition of synthesized schiff base N,N′-bis(3,5-dihydroxyacetophenone)-2,2-dimethylpropandiimine on API-5L-X70 steel in hydrochloric acid solutions were used to study the effects of drifts removal methods on noise resistance calculation. Also, electrochemical impedance spectroscopy (EIS) was used to study the corrosion inhibition property of the inhibitor. The results showed that for the calculation of R n , both methods were effective in trend removal and the polynomial with m=4 and MAR with p=40 were in agreement.
The inhibition ability of N,N-bis(2,4-dihydroxyhydroxybenzaldehyde)-1,3-Propandiimine (DHBP) as a schiff base against the corrosion of API-5L-X65 steel in 1 M HCl solution was evaluated by electrochemical impedance spectroscopy, potentiodynamic polarization and scanning electron microscopy. Electrochemical impedance studies indicated that DHBP inhibited corrosion by blocking the active corrosion sites. The inhibition efficiency increased with increasing inhibitor concentrations. EIS data was analysed to equivalent circuit model and showed that the charge transfer resistance of steel increased with increasing inhibitor concentration whilst the double layer capacitance decreased. The adsorption of this compound obeyed the Langmuir adsorption isotherm. Gibbs free energy of adsorption was calculated and indicated that adsorption occurred through physical and spontaneous process. The corrosion inhibition mechanism was studied by potential of zero charge. Polarization studies indicated that DHBP retards both the cathodic and anodic reactions through adsorption on steel surface. Scanning electron microscopy was used to study the steel surface with and without inhibitor.
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