Separation of Phenol from Waste Water by the Liquid Membrane Technique

Extraction of methylene blue from aqueous solution by pickering emulsion liquid membrane using cellulose as eco-friendly emulsifier: optimization and modeling studies

In the present investigation cellulose, a naturally occurring biopolymer, was used as an eco-friendly emulsifier for the removal of methylene blue (MB) from simulated wastewater using emulsion liquid membrane. Coconut oil, a green diluent, was used as an organic phase in preparing a pickering emulsion liquid membrane (PELM) the extraction of dye. The PELM was prepared by loading with aliquat 336 as extractant, potassium hydroxide (KOH) as internal phase, and edible coconut oil as the diluent. The effect of the process parameters such as dye concentration, internal phase concentration, emulsifier concentration, organic phase to aqueous phase (O/A) ratio, stirring speed (RPM) were studied using Box-Behnken design and response surface method. The results showed that more than 92% of MB were successfully extracted around 120 min. Hence, it could be concluded that cellulose can be used as a promising emulsifying agent in the PELM preparation for the removal of MB from wastewater.

Operational Limits of the Bulk Hybrid Liquid Membranes Based on Dispersion Systems

Liquid membranes usually have three main constructive variants: bulk liquid membranes (BLM), supported liquid membranes (SLM) and emulsion liquid membranes (ELM). Designing hybrid variants is very topical, with the main purpose of increasing the flow of substance through the membrane but also of improving the selectivity. This paper presents the operational limits of some kind of hybrid membrane constituted as a bulk liquid membrane (BLM), but which works by dispersing the aqueous source (SP) and receiving (RP) phases, with the membrane itself being a dispersion of nanoparticles in an organic solvent (NP–OSM). The approached operational parameters were the volume of phases of the hybrid membrane system, the thickness of the liquid membrane, the working temperature, the flow of aqueous phases, the droplet size of the aqueous phases dispersed across the membrane, the nature and concentration of nanoparticles in the membrane, the pH difference between the aqueous phases, the nature of the organic solvent, the salt concentration in the aqueous phases and the nature of transported chemical species. For this study, silver ion (SI) and p-nitrophenol (PNP) were chosen as transportable chemical species, the n-aliphatic alcohols (C6…C12) as membrane organic solvents, 10–undecenoic acid (UDAc) and 10-undecylenic alcohol (UDAl) as carriers and magnetic iron oxides as nanoparticles dispersed in the membrane phase. Under the experimentally established operating conditions, separation efficiencies of over 90% were obtained for both ionic and molecular chemical species (silver ions and p-nitrophenol). The results showed the possibility of increasing the flow of transported chemical species by almost 10 times for the silver ion and approximately 100 times for p-nitrophenol, through the appropriate choice of operational parameters, but they also exposed their limits in relation to the stability of the membrane system.

Accessible Silver-Iron Oxide Nanoparticles as a Nanomaterial for Supported Liquid Membranes

The present study introduces the process performances of nitrophenols pertraction using new liquid supported membranes under the action of a magnetic field. The membrane system is based on the dispersion of silver–iron oxide nanoparticles in n-alcohols supported on hollow microporous polypropylene fibers. The iron oxide–silver nanoparticles are obtained directly through cyclic voltammetry electrolysis run in the presence of soluble silver complexes ([AgCl₂]⁻; [Ag(S₂O₃)₂]³⁻; [Ag(NH₃)₂]⁺) and using pure iron electrodes. The nanostructured particles are characterized morphologically and structurally by scanning electron microscopy (SEM and HFSEM), EDAX, XRD, and thermal analysis (TG, DSC). The performances of the nitrophenols permeation process are investigated in a variable magnetic field. These studies show that the flux and extraction efficiency have the highest values for the membrane system embedding iron oxide–silver nanoparticles obtained electrochemically in the presence of [Ag(NH₃)₂]⁺ electrolyte. It is demonstrated that the total flow of nitrophenols through the new membrane system depends on diffusion, convection, and silver-assisted transport.

Graphene Oxide-Based Nanofiltration for Hg Removal from Wastewater: A Mini Review

Mercury (Hg) is one of heavy metals with the highest toxicity and negative impact on the biological functions of living organisms. Therefore, many studies are devoted to solving the problem of Hg separation from wastewater. Membrane-based separation techniques have become more preferable in wastewater treatment area due to their ease of operation, mild conditions and also more resistant to toxic pollutants. This technique is also flexible and has a wide range of possibilities to be integrated with other techniques. Graphene oxide (GO) and derivatives are materials which have a nanostructure can be used as a thin and flexible membrane sheet with high chemical stability and high mechanical strength. In addition, GO-based membrane was used as a barrier for Hg vapor due to its nano-channels and nanopores. The nano-channels of GO membranes were also used to provide ion mobility and molecule filtration properties. Nowadays, this technology especially nanofiltration for Hg removal is massively explored. The aim of the review paper is to investigate Hg removal using functionalized graphene oxide nanofiltration. The main focus is the effectiveness of the Hg separation process.

Effect of contacting pattern and various surfactants on phenol extraction efficiency using emulsion liquid membrane

Emulsions prepared using different surfactants, including Span-80, BKC and CTAB, are studied for their stability and phenol remsoval efficiency. The effect of contacting pattern on ELM extraction efficiency is compared in Beaker – Stirrer apparatus and Bubble Flow Recirculation column. The emulsion prepared using Span-80 is relatively more stable than emulsions prepared using other surfactants. The emulsion stability during the extraction process is relatively higher in the Bubble Flow Recirculation column (15 min) than in the Beaker – Stirrer apparatus (10 min). At optimized conditions, the phenol removal efficiency of the emulsion prepared using Span-80 in Beaker – Stirrer apparatus is 96% and in Bubble Flow Recirculation column is 78%. Kinetic studies reveal that the extraction follows zeroth-order kinetics with an average phenol effective diffusivity of 0.0004 s at an initial phenol concentration ranging from 100–500 PPM.

Interfacial Solvation and Surface pH of Phenol and Dihydroxybenzene Aqueous Nanoaerosols Unveiled by Aerosol VUV Photoelectron Spectroscopy

Although the significance of aqueous interfaces has been recognized in numerous important fields, it can be even more prominent for nanoscaled aqueous aerosols because of their large surface-to-volume ratios and prevalent existence in nature. Also, considering that organic species are often mixed with aqueous aerosols in nature, a fundamental understanding of the electronic and structural properties of organic species in aqueous nanoaerosols is essential to learn the interplay between water and organic solutes under the nanoscaled size regime. Here, we report for the first time the vacuum ultraviolet photoelectron spectroscopy of phenol and three dihydroxybenzene (DHB) isomers including catechol, resorcinol, and hydroquinone in the aqueous nanoaerosol form. By evaluating two photoelectron features of the lowest vertical ionization energies originated from the b₁(π) and a₂(π) orbitals for phenolic aqueous nanoaerosols, their interfacial solvation characteristics are unraveled. Phenolic species appear to reside primarily on/near the aqueous nanoaerosol interface, where they appear only partially hydrated on the aqueous interface with the hydrophilic hydroxyl group more solvated in water. An appreciable proportion of phenol is found to coexist with phenolate at/near the nanoaerosol interface even under a high bulk pH of 12.0, indicating that the nanoaerosol interface exhibits a composition distribution and pH drastically different from those of the bulk. The surface pH of phenol-containing aqueous nanoaerosols is found to be ∼2.2 ± 0.1 units more acidic than that of the bulk interior, as measured at the bulk pH of 12.0. From the photoelectron spectra of DHB aqueous nanoaerosols, the effects of numbers/arrangements of -OH groups are assessed. This study shows that the hydration extents, pH values, deprotonation status, and numbers/relative arrangements of -OH groups are crucial factors affecting the ionization energies of phenolic aqueous nanoaerosols and thus their redox-based activities. The multifaceted implications of the present study in the aerosol science, atmospheric/marine chemistry, and biological science are also addressed.

Adsorption and catalytic oxidation of phenol in a new ozone reactor

Phenolic wastewater treatment in a new ozone reactor was investigated. The reactor was designed in such a fashion that gas induction was created in the reactor headspace by the high-speed action of an impeller turbine inside a draft tube to maximize the ozone utilization. Another important feature of the present reactor design was incorporation of granular activated carbon bed in a circular compartment between the reactor wall and the shaft tube. The fixed granular activated carbon bed was observed to significantly enhance the phenol decomposition and the chemical oxygen demand removal when compared to gas-induced ozonation alone, providing evidence of the synergistic effects of adsorption, catalytic reaction and ozonation. In addition to the enhanced phenol decomposition and chemical oxygen demand, ozonation was found to provide in-situ regeneration of granular activated carbon which was considered crucial in the present reaction system. Kinetic investigations were also made using a proposed complex kinetic model in an attempt to elucidate the possible decomposition reaction mechanisms of the present gas-induced ozonation system.

Microencapsulation of hemoglobin in liposomes using a double emulsion, film dehydration/rehydration approach

A double emulsion, film dehydration/rehydration approach was developed for encapsulation of hemoglobin (Hb) at high concentration in liposomes. The liposome-encapsulated Hb (LEH) membrane was formulated to contain either phosphatidylinositol (PI) or polyethyleneglycol phosphatidylethanolamine (PEG-PE) along with partially hydrogenated egg-PC, cholesterol, and alpha-tocopherol in a molar ratio of 0.1:1:1:0.02, respectively. The methods introduced in this study followed a multi-step procedure. First, a primary emulsion of Hb in organic solvent containing dissolved lipids was formed. Next, the emulsion was dispersed into an aqueous continuous phase to form a water-in-oil-in-water type double emulsion. Other than the lipids noted above, no surfactants were used in this system. The double emulsion was then converted to LEH by the following steps: evaporating the organic solvent; dehydrating the water to form a dry, thin Hb-lipid film; rehydrating the film in Hb solution to form the LEH; reducing the size of the LEH using 'microfluidization' i.e., high pressure/hydrodynamic shear; and lastly washing the down-sized LEH in buffer. Physico-chemical properties of the model LEH were measured, including oxygen content, encapsulated Hb concentration, oxygen affinity and cooperativity, vesicular size distribution, viscosity, and stability. The suitability of LEH prepared in this manner as a red blood cell substitute was shown using continuous isovolemic exchange transfusion techniques in a small animal model: clearance, efficacy and acute toxicity were evaluated.