Ultrasonication-assisted preparation of water-in-oil emulsions and application to the removal of cationic dyes from water by emulsion liquid membrane

Abstract

a b s t r a c tThe main objective of this work is the utilization of W/O emulsions prepared by low-frequency ultrasonic irradiation (22.5 kHz) for the removal and recovery of cationic dyes from aqueous solution by emulsion liquid membrane containing di(2-ethylhexyl) phosphoric acid (D2EHPA) as carrier. The important parameters governing the extraction behavior of dyes have been investigated. These parameters were contact time of the external phase with W/O emulsions, external phase concentration, feed phase pH, stirring speed, extractant concentration, presence of salts, and type of diluent. The extraction of a mixture of four cationic dyes (methylene blue, rhodamine B, malachite green, and basacryl red GL) is also investigated in the absence and presence of salt in the external phase. The possibility of stripping the dyes is evaluated and the influence of sulfuric acid concentration on the stripping efficiency is also examined. The obtained results show that, under most favorable conditions, practically all the dye cations present in the feed phase were extracted. The removal percentage of the mixed dye was found to be higher than 98% even in the presence of salt in the continuous phase. The transport mechanism of cationic dyes for the present system was determined and divided into six stages. The best sulfuric acid concentration in the internal phase that conducted to very good stripping efficiency (≥97%) and excellent emulsion stability was 0.5 M. In all cases, the recovery of the membrane phase was total and the extraction of dyes was not decreased up to seven runs.

Performance evaluation of organic emulsion liquid membrane on phenol removal

“…Higher emulsification speed yielded smaller size of emulsion liquid droplets which make the emulsion more efficient to extract phenol from the external aqueous phase. According to Djenouhat et al [20] and Gasser et al [22], smaller size of emulsion liquid droplets gave better dispersion in the external phase while providing more interfacial surface area for mass transfer. They also suggested that high emulsification speed gave good dispersion of internal phase in the membrane phase, thus providing better emulsion stability with lower leakage due to the higher coalescence time.…”

“…For emulsion liquid membrane (ELM) preparation, several publications [9,11,14,19,20,22,23] were referred to. Span 80 was used as a surfactant for ELM due to its popularity as an emulsifier for liquid membrane while Cyanex 923 was proposed to be the carrier for extraction of phenol [10,11,24,25].…”

“…With the objective of increasing emulsion stability, Park and Chung [9] and Mortaheb et al [14] tested different surfactants on ELM and it was found that the emulsion stability can be enhanced by increasing the surfactant concentration. Other researchers [9,13,14,20] have reported their works on the enhancement of emulsion stability and efficiency through the addition of stabilizer such as PIB, different emulsification methods and vortex column operation. In addition to the parameter mentioned, there are several other parameters that can influence emulsion stability such as volume ratio, temperature, stirring speed, internal stripping agent concentration, surfactant concentration, pH [9,[12][13][14][21][22][23].…”

Extraction of Priority Pollutant 4-Nitrophenol from Water by Emulsion Liquid Membrane: Emulsion Stability, Effect of Operational Conditions and Membrane Reuse

“…The increase of droplets diameter decreases the interfacial contact area between the emulsion and feed phase and thereby decreases the extraction. Additionally, for higher volume ratios, the volume of organic phase is not enough for enclosing all the internal aqueous phase [22][23][24] and the dispersion of the W=O emulsion was more difficult. From these results and in order to obtain a uniform and homogeneous distribution of the internal phase droplets in the membrane space and a good dispersion of the W=O emulsion in external phase, the volume ratio of internal phase to membrane phase of 1=1 was accepted as the best ratio.…”

Recovery of kraft lignin from pulping wastewater via emulsion liquid membrane process

“…In addition, the extended emulsifying process led to the rupture of emulsion and this was probably caused by the coalescence of the internal droplets and the high shearing rate. In addition, according to Chiha et al, prolonged exposure to emulsifying resulted in a significant increase of breakage . As a result, emulsifying time of 5 min was found to be sufficient for emulsification to obtain a stable emulsion for extraction of KL.…”