Taleb H. Ibrahim

Direct adhesion measurements of pharmaceutical particles to gelatin capsule surfaces

Scanning probe microscopy (SPM) was used to measure directly the adhesion of individual lactose particles to the surface of gelatin capsules employed in dry powder inhalant drug delivery systems. In this study, SPM shows that gelatin capsule surfaces with high surface heterogeneity and high-contrast friction exhibit high adhesion and that gelatin capsule surfaces with low surface heterogeneity and low-contrast friction exhibit low adhesion. The adhesion of lactose particles to gelatin capsules was also determined by measuring the retention of lactose particles in the capsules. The adhesion trend obtained with individual lactose particles using the colloidal probe technique agrees with the macroscopic retention results. The adhesion appears to be proportional to the particle size for homogeneous capsule surfaces. In dry powder inhalation products, the Lifshitz-van der Waals forces and acid-base interactions appear to be the principal forces contributing to particle-surface adhesion. The physicochemical nature of the capsule surface seems to dictate the spatial variation of adhesion across the surface. The SPM results clearly show that the surface physicochemical properties depend on the gelatin and mold release agent utilized in the manufacture of gelatin capsules. One of the practical implications of this study is that extraneous surface contamination of gelatin capsules by chemical processing aids such as mold release agents appears to be a key factor affecting the respirable fraction in dry powder inhalation products.

Particulates and bacteria removal by ceramic microfiltration, UV photolysis, and their combination

Membrane microfiltration (MF) or ultrafiltration (UF) systems of activated sludge is crucial part of a bioreactor process used in municipal wastewater treatment. In this study, both cylindrical and flat sheet ceramic membranes were used to treat municipal wastewaters. The effects of removing water turbidity and coliform bacteria from an artificial wastewater were studied by performing batch experiments by MF and ultraviolet (UV) photolysis of 254 nm wavelength. It was shown that the microfiltration had a high effect of suspended solid removal. However, the effect of bacteria removal was limited so that the rate of cfu removal was approximately 61%. Combined consecutive processes in the treatment (MF/UV and UV/MF) confirmed that a specific porosity of the ceramic filter for bacteria removal was required. The continuous membrane bioreactor (MBR) tests performed by using a MF membrane with the pore size of 0.2 μ m showed that particulate matter and microorganisms found in municipal wastewater could be effectively removed. Turbidity was decreased from 4.50 to 0.05 NTU, with a removal efficiency of greater than 98%. The permeate total suspended solid (TSS) content for the whole run was below 5 mgL− 1. The density of total coliforms was decreased more than four orders of magnitude (from around 1× 105 mL− 1 to less than 5 mL− 1 in the effluent).

An Overview of the Physiochemical Nature of Metal-Extractant Species in Organic Solvent/Acidic Organophosphorus Extraction Systems

The interfacial behavior of metal-extractant species in the liquid/liquid extraction of metal ions still remain incompletely understood at the molecular level under high loading conditions. Traditionally, metal-extractant complexes in the organic phase under dilute conditions have been characterized by slope analysis. At high loading, the metal-extractant aggregates structure appears to change. The metal-extractant aggregates have been described as either polymers or reversed micelles. This behavior is difficult to confirm by direct experimental measurements. Recently, molecular modeling was used to study the molecular structure of metal-extractant aggregates. The study confirmed that the metal-extractant species are reversed micelles at high loading conditions.

Role of water molecules in sodium bis(2-ethylhexyl) phosphate reversed micelles in n-heptane

Abstract Recently molecular modeling was employed on the metal-extracted aggregates that form during the liquid/liquid extraction of transition metals. During the extraction process, the aqueous phase pH is adjusted with sodium hydroxide. In additional to the formation of the transition metal-extractant reversed micelles, sodium-bis(2-ethylhexyl) phosphate (NaDEHP) reversed micelles can also form. According to the classical model of reversed micelles, water molecules act as promoters for the formation of reversed micelles. Water molecules act as “gluing” agents for micellization in apolar media. Here we report a unique finding about the role of water molecules in reversed micellar aggregates using molecular modeling. The molecular modeling of the reversed micellar system of NaDEHP in n-heptane clearly shows that water molecules can act as an “antimicellization” agent. Water molecules have no gluing effect on the formation of NaDEHP reversed micelles. In fact, large NaDEHP reversed micelles are formed in “dry” conditions.

Corrosion inhibition of mild steel by Calotropis procera leaves extract in a CO2 saturated sodium chloride solution

Abstract The Calotropis procera leaves extract (CPLE) was investigated as a corrosion inhibitor for mild steel in a CO2-saturated 3.5 wt% NaCl solution using various electrochemical techniques. The results show that the CPLE is an effective inhibitor with inhibition efficiency of 80% using 50 ppm. Polarization studies show that the CPLE acts as a mixed inhibitor, and the adsorption of CPLE follows Langmuir adsorption isotherm. Molecular dynamics simulations reveal that the presence of N, O in the CPLE as well as π-electron systems coupled with high adsorption energies of interaction of the CPLE with steel are responsible for corrosion inhibition performance.

Removal of Lead (II) Ions from Aqueous Solution Using Eggplant Peels Activated Charcoal

The eggplant peel activated charcoal (EPPAC) was investigated as an adsorbent for the removal of lead II ions from aqueous solution. Three methods were tested for the production of eggplant peel activated charcoal (EPPAC) from eggplant peel charcoal (EPPC), yielding three different products; EPPAC-1, EPPAC-2, and EPPAC-3. The difference among the three methods lies in the primary physical mixing of the EPPC with the activating agent (potassium hydroxide) before heating the mixture in a furnace for activation. The removal efficiency of lead II ions by the three adsorbents was 57.7%, 70.0%, and 60.0% for EPPAC-1, EPPAC-2, and EPPPAC-3, respectively. The optimized activation parameters for EPPAC-2 were: activation time 2 hours, activation temperature 700°C, and activation ratio 1:2 (EPPAC: KOH). Scanning electron microscopy (SEM) revealed that EPPAC-2 has the most porous structure. The surface area of EPPAC-2 was measured to be 739 m2/g. Adsorption kinetics of lead (II) is best described by the pseudo-second-order kinetic model with second order rate constant of 1.70 × 10−3 g/mg.h at room temperature. The adsorption of lead on EPPAC-2 is found to follow the Langmuir isotherm with a maximum adsorption capacity of 1.4 × 102 mg/g.

Mild steel green inhibition by Ficus carica leaves extract under practical field conditions

Abstract Various electrochemical techniques were employed to study the effectiveness of aqueous Ficus carica (Fig. tree) leaves extract as green corrosion inhibitor for mild steel under field conditions containing 3.5% sodium chloride solution saturated with carbon dioxide. Optimum inhibition efficiency of 90% was obtained using 50 mg/L of inhibitor in the temperature range of 25–40 °C. The mode of action of Ficus carica leave extract as revealed by Polarization studies was shown to act as a mixed inhibitor. The adsorption isotherm of the adsorption of Ficus carica leaves extract on the steel surface was found to follow Langmuir adsorption isotherm. In order to assess the individual contribution of the different constituents of the extract theoretically, the adsorption of the four major organic constituents of Ficus carica leave extract on mild steel were modelled using density functional theory and quench molecular dynamic simulations. Among the four major Ficus carica leaves extract constituent investigated, Caffeoylmalic acid was found to make the most contribution to the overall inhibition action of Ficus carica leaves extract.

Application of multiwalled carbon nanotubes and its magnetite derivative for emulsified oil removal from produced water

ABSTRACT Multiwalled carbon nanotubes and their magnetite derivatives were employed as adsorbents for emulsified oil removal from produced water. The experimental parameters for maximum emulsified oil removal efficiency and effective regeneration of these adsorbents were determined. The optimum parameters in terms of adsorbent dosage, contact time, salinity, pH and temperature were 3.0 g/L, 20.0 min, 0 ppm, 7.0 and 25°C for both adsorbents. Due to their low density, multiwalledcarbon nanotubes could not be successfully employed in packed bed columns. The magnetite derivative has a larger density and hence, for the removal of emulsified oil from produced water packed bed column studies were performed utilizing multiwalled carbon magnetite nanotubes. The packed bed column efficiency and behaviour were evaluated using Thomas, Clark, Yan et al. and Bohart and Adams models. The Yan model was found to best describe the column experimental data. The adsorbents were regenerated using n-hexane and reused several times for oil removal from produced water without any significant decrease in their initial adsorption capacities. GRAPHICAL ABSTRACT