Mentha Piperita Extract as a Natural Product for the Corrosion Inhibition of Low Carbon Steel in a Polluted NaCl Environment: Chemical, Electrochemical and Biological Studies

The impact of aqueous Mentha Piperita Extract (MPE) as a corrosion inhibitor for low carbon steel (LCS) in NaCl/Na2S solution was investigated using chemical and electrochemical techniques to evaluate the protection performance of MPE. “As the concentration of the extract increased, the protection efficiency (PE) increased, reaching 91.2% at 300 ppm, whereas the increase in temperature favored to slow decrease”. The extract was physically adsorbed on the metal surface according to the Temkin isotherm. Polarization data revealed that this extract acts as a mixed inhibitor. The mechanism of corrosion protection of MPE was discussed from electrochemical techniques. MPE was adsorbed on LCS obeying Temkin isotherm. Surface morphology techniques such as scanning electron microscopy (SEM) and atomic force microscopy (AFM) were used to demonstrate the creation of a protective coating on the LCS in the presence of MPE. The extract inhibits the bacterial activity of Escherichia coli.

KINETICS, EQUILIBRIUM AND MECHANISMS OF NI (II) AND Pb (II) ION BIOSORPTION USING BIOSORBENT MIXTURE OF RHIZOPHORA APICULATE SP. AND ELAEIS GUINEENSIS SP.

The existence of metal ions in water supply has become a severe issue and created an awareness in order to find the significant methods for the removal of heavy metals (HM). In this study, the biosorbent used are Oil Palm Mesocarp Fibe (OPMF) (Elaeis guineensis sp.) and Mangrove Bark (Rhizophora apiculate sp.). These biosorbents mixed to form the biosorbent mixture (BM) to enhance the biosorption performance towards Ni (II) and Pb (II) ions. Four parameters applied to investigate the biosorption performance, i.e. reaction time, ratio/dosage, initial concentration and pH values. The biosorption performance for Pb (II) (90%, 5.7mg/g) was higher than Ni (II) (55%, 3.9mg/g). Five kinetic models were exercised to investigate the kinetic mechanisms namely pseudo-first and second-order, Bangham's theory, intra-particles diffusion and Elovich equation. The isotherm models viz. Langmuir, Freundlich, Dubinin-Radushkevich and Temkin Isotherm exercised to analyse the equilibrium biosorption data. Overall, pseudo-second-order discovered to act as biosorption kinetics for both Ni (II) and Pb (II) ions. The equilibrium biosorption data of Pb (II) was followed Temkin Isotherm, and Ni (II) supported by Freundlich Isotherm.

Kinetic Study, Modelling and Optimization of Adsorption Processes for Removal of Crude Oil from Contaminated Water using Chitosan-Rice Husk Ash Composite

This study was aimed at developing chitosan-rice husk ash adsorbent for the removal of crude oil from contaminated water. Design Expert software 6.06 was used to design the adsorption experiment. The adsorption was tested for Langmuir, Freundlich and Temkin isotherms and the kinetic studies also carried out. The effect of influencing parameters such as contact time, adsorbate concentration, adsorbent dosage and formulation ratio were studied. It was generally shown that adsorption process increased with time and adsorbate concentration and decreased with adsorbent dosage. Models for the prediction of adsorption capacity for the composite was significant with R2 value of 0.8382 and P-value of 0.0017. Optimum conditions were found to be 0.90 wt/wt chitosan/silica ratio, contact time of 5 min, and oil/water ratio of 0.25 v/v, which gave 20.66 g/g sorption capacity respectively. Adsorption isotherm studies of Langmuir, Freundlich and Temkin were carried out for the chitosan-rice husk ash composite. Temkin isotherm best fitted with R2 value of 0.9999. The adsorption capacity of composite from isotherm studies was obtained to be 18.85 g/g adsorbent. The heat of adsorption bT (kJmol-1) obtained from Temkin isotherm study was -48.67 kJ/mol indicating physisorption of adsorbents to the crude oil. Kinetic studies indicated that the pseudo-second order model suitably described the removal of crude oil by the composite with R2 value 0.9999.

Application of Freundlich and Temkin Isotherm to Study the Removal of Pb(II) Via Adsorption on Activated Carbon Equipped Polysulfone Membrane

The aim of this study was to investigate the application of membrane equipped activated carbon for heavy metal removal. An adsorption capacity of the activated carbon inside membrane matrix was performed against environmentally problematic ions specifically Pb2+, in aqueous solution. The adsorption process was examined by Temkin and Freundlich isotherm. From the SEM observation, membrane exhibit sponge-like structure with dense micro-void formation across the matrix. This phenomenon was usually observed with membrane mixed with polyethyleneimine. For the adsorption studies, it is shown that Freundlich isotherm show better fit based on R2 value of 0.9893 with Temkin isotherm fitted with R2 of 0.9009. Through the fitted model, the adsorption occur on the surface of activated carbon are possibly multilayer type adsorption based on theory by Freundlich isotherm and fall under non-ideal reversible adsorption.

Study on the Adsorptive Solute Cr(VI) Loss from Soil to Surface Runoff with Temkin Adsorption

Based on the water balance and solute mass conservation, a simple two-layer incomplete mixing model by Tong et al. (2009) is used to study adsorptive solute of Cr (VI) loss from soil into surface runoff with nonlinear Temkin adsorption. Laboratory experimental data are used to verify the model with nonlinear Temkin isotherm adsorption equation. Study results suggest that model simulations with Temkin isotherm equation agree well with the observed data, which means that the model is valid. The sensitivity of the model parameters were analyzed, which shows that the mixing parameters γ and α are more sensitive to the soil solute of Cr (VI) loss to surface runoff while the parameter B1 and A1 of adsorption equation is less sensitive. The solute of Cr (VI) loss to surface runoff is decreasing with increasing θ0, while soil bulk density is vice verse. The study results will provide references to prevent soil solute of Cr (VI) pollution to surface water system.

Determination of Adsorption Isotherm model best fit for methanol leaf extract of Securinega virosa as corrosion inhibitor for corrosion of mild steel in HCl

The adsorption isotherm model best fit of the methanol leaf extract of Securinega virosa as corrosion inhibitor for the corrosion of mild steel in 2 M HCl medium was determined with the assistance of the Adejo-Ekwenchi adsorption isotherm. The corrosion inhibition study was carried out using the weight loss method at the temperature range of 301 K to 313 K. The inhibition efficiency, %IE, of the extract was found to increase with increase in both concentration and temperature. On the account of, R2 this adsorption process well fitted into Langmuir, Freundlich, Temkin isotherm, Flory-Huggins and Adejo-Ekwenchi models. However, through the parameter b of the Adejo-Ekwenchi isotherm, which clearly shows the adsorption process to be chemisorption, the best isotherm fit for the extract has been resolved to be the Langmuir isotherm and Temkin isotherm models.

Two-Section Model for Adsorption of Tinidazole on Carbon Steel Surface in 3%HCl Solution

This paper has reported a two-section model based on Temkin isotherm for interpreting the adsorption and inhibition properties of tinidazole on 45# carbon steel surface. The results show that the repulsion behavior between the adsorbed molecules turns into interattraction as the concentration of inhibitor is over 400mg/L. And additionally, the withdrawal of adsorbed molecules back into the bulk solution becomes thermodynamically favorable due to the formation of hemi-micelles.