ABSTRACT
Removal of phenol from industrial effluents was studied using the emulsion liquid membranes. A multiple W1/O/W2 emulsion is prepared where the intermediate "O" represents oil phase acting as membrane; W1 and W2 are aqueous phases
W2 is the external aqueous phase from which phenol is to be removed and Wl is the aqueous NaoH phase which receives the phenol that got transported across the membrane oil phase. Emulsifier used in preparing the emulsion is Span 80
The effect of various parameters such as stirring speed, oil phase to aqueous phase ratio in emulsion, surfactant concentration, internal reactive phase concentration in the emulsion, treat ratio (ratio of emulsion to waste water phase), initial phenol concentration, effect of change in membrane phase, temperature on the rate of removal of phenol were studied
Studies pertaining to selling of emulsions due to penetration of water into the emulsion were also conducted and it is found that this phenomenon is primarily responsible for breakage of the dispersed emulsion drops during the operation. With the help of data obtained from this work an optimal recipe for the membrane can be identified which could be conveniently used to design liquid emulsion membrane based separation systems for phenol removal from the waste water streams
INTRODUCTION
Phenol is key effluent from various industries like pharmaceuticals, pesticides & paper and pulp industries, dyes manufacturing, synthetic chemicals
Phenol is a colorless-to-white/ light pink solid when pure; however, the commercial product, which contains some water, is a liquid. Phenol has a distinct odour that is sickeningly sweet and tarry
Techniques used for removal of phenol from waste water
Emulsion liquid membranes
Other than the above process Adsorption, Solvent extraction, Electrochemical reduction
Biological degradation can also be used for phenol removal
Effects of phenol on living organisms:
All forms of phenol cause irritation, and acute toxic effects of phenol most often occur by skin contact. Even dilute solutions. (1% to 2%) may cause severe burns if contact is prolonged. Toxicity can result from skin or eye exposures. Phenol vapor and liquid penetrate the skin with absorption efficiency approximately equal to the absorption efficiency by inhalation. In one case, death occurred within 30 minutes after skin contact. Children are more vulnerable to toxicants absorbed through the skin because of their relatively larger surface area: body weight ratio.
As little as 50 to 500 mg has been fatal in infants. Deaths in adults have resulted after ingestions of 1 to 32 g. Phenol is corrosive and causes chemical burns at the contact site. Other symptoms include nausea, vomiting, diarrhea, profuse sweating, and hypotension.
Severe effects of phenol exposure:
As a corrosive substance, phenol denatures proteins and generally acts as a protoplasmic poison. Phenol may also cause peripheral nerve damage. Systemic poisoning can occur after inhalation, skin contact, eye contact, or ingestion. Damage to the nervous system is the primary cause of death from phenol poisoning.
Membranes:
The purpose of adopting the membrane process could be either concentrating the feed by preferential permeation of sol vent or diluting the feed by preferential permeation of solute.
Membrane is defined as "A Selective barrier between two phases", and the term "Selective" being inherent to a membrane or a membrane process or it is defined as "A thin film (0.1 to 0.4mm) of polymeric or inorganic material capable of preferentially allowing some components of the feed mixture to pass through it compared to other components.
Classification of membranes:
The other basic type of classifying membranes is by separation is porous, non-porous and carrier membranes
Generally speaking membranes can be classified as follows
• Porous membranes
• Dense membranes
• Carrier membranes
• Composite membranes
• Insitu formed membranes
• Ion exchange membrane
• Atmospheric membranes and
• Redox membranes
Multiple emulsions as Lm's:
The liquids which are immiscible with each other in the membrane technology are usually water and oils. The formation of an emulsion is favored fundamentally by a reduction of the interfacial tension between the two immiscible liquids. The edition of a surface active material (surfactant) causes this desired reduction. A surfactant molecule must have an amphiphilic molecular structure, such that one part of the molecule is lyophilic (non-polar structure). The hydrophilic part of the surfactant molecule resides in water and the lyophilic part in the oil
Good .surfactants can reduce the interfacial tension by a factor of 5 or 10. In general, the surfactant dissolves better in one of the two liquids (oil and water) as a result of which the surface tension of that substance is strongly reduced and greater mobility is to be expected.
The emulsion liquid membrane (ELM) as a selective technique has large potential for application
in wastewater treatment. ELM technique is applied both for waste waters containing organic (or) inorganic pollutants and with pollutant mixtures [3]. This method is especially applicable for heavy metal separation from aqueous solutions. In addition, the treated water can be recycled in the process. The membrane method has been applied to treat water containing ferrous and non-ferrous metals, alkaline metals, radioactive elements, rare metals etc.
Elms are usually multiple emulsions of the water/oil/water type. To obtain this, a fine emulsion of the stripping phase in the membrane phase is produced and stabilized by a surfactant. The resulting water-in-oil emulsion is then dispersed by gentle stirring in the feed solution to create a double emulsion
