Arnel B. Beltran

Dye/water separation through supported liquid membrane extraction

The separation of synthetic dye Rhodamine 6G (R6G) and water was investigated using blended organic liquids in a supported liquid membrane (SLM) extraction system. Liquid membrane (LM) components include octyl alcohol (OcOH) as the dye extractant and a polysiloxane liquid as the stabilizing agent. Initial permeation results revealed the suitability of poly (phenyl methyl) siloxane (PPMS) over poly (octyl methyl) siloxane as the blending agent. The most acceptable condition for dye extraction was determined at feed solution pH congruent with 1, wherein highest distribution coefficient, K(D) (OcOH/H(2)O)=18, was attained. Though permeability decreased at optimal blending condition of 1:1 (w/w) OcOH/PPMS, SLM longevity was exhibited with>98% LM retention after 15 h operation in contrast to pure OcOH SLM system (>60% LM loss). Equilibrium experiments reveal that dye extraction followed Langmuir adsorption principle. The dye transport was elucidated using mass transfer analysis wherein it showed a decrease in overall coefficient (k(o)) at increasing feed concentrations. This was a direct consequence of K(D) decline, which becomes more apparent at higher concentrations when SLM saturation point is approached. At varied hydrodynamic conditions, improved k(o) values were observed up to Re(omega)=10,000 when minimal variation in film resistance is attained. Beyond this condition, k(o) becomes independent from stirring rate effect nonetheless SLM stability is compromised due to shear-induced LM losses.

Silver nanoparticles in a polyether - block - polyamide copolymer towards antimicrobial and antifouling membranes

The potential of hydrophilic polyether-block-polyamide copolymer (PEBA) with antimicrobial silver nanoparticles (nano-Ag) to alleviate membrane biofouling was investigated. PEBA solutions of different nano-Ag content were prepared as dense films and as coating materials for ultrafiltration polysulfone (PSf) membranes. Disc diffusion and surface contact tests revealed the capability of the PEBA/nano-Ag films to inhibit the growth of Escherichia coli (E. coli). Contact angle measurements confirmed the hydrophilisation of the PSf surface after coating with PEBA. Field emission scanning electron microscopy, atomic force microscopy (AFM) and fourier transform infrared spectroscopy were performed to confirm the surface modification of PSf. As a proof-of-concept, filtration performances of bare PSf, PEBA coated-and PEBA/nano-Ag coated PSf were compared using a simulated solution inoculated with E. coli as the feed. The results revealed that the hydrophilisation of PSf by coating with PEBA improved the fouling resistance of the membrane as indicated by the retarded flux reduction rate and higher flux recovery. However, PSf exhibited the highest antifouling resistance when coated with PEBA/nano-Ag. The AFM images of used membranes showed that PEBA/nano-Ag minimized the attachment and growth of E. coli on the membrane which abated irreversible biofouling, a problem that was most severe on bare PSf.

Liquid–liquid extraction of Li+ using mixed ion carrier system at room temperature ionic liquid

AbstractAn environmentally benign technique for the separation and recovery of lithium (Li+) from aqueous streams, containing mixed metal ions was developed via liquid–liquid extraction (LLE). Hydrophobic room temperature ionic liquids (RTIL) were tested as the main extracting solvents. To increase the metal extraction, a proton-ionizable agent bis(2-ethylhexyl) phosphoric acid (DEHPA) was added into the RTIL. To enhance the metal uptake selectivity, three Li+-selective neutral ion carriers such as 6-hydroxy-dibenzo-14-crown-4, dibenzo-14-crown-4, and tri-n-octyl-phosphine (TOPO) were also used and tested as extractant additives. Among the tested RTILs, phosphonium-based CYPHOS IL 109 was the most stable extractant as it exhibited the lowest loss when contacted with water. Addition of proton-ionizable agent DEHPA in CYPHOS IL 109 afforded a high extraction of multivalent cations with negligible recovery of monovalent metals. On the other hand, the addition of neutral ion carrier TOPO in DEHPA/CYPHOS IL 10...

Microwave-Assisted Synthesis of Dibenzo-Crown Ethers

The present invention relates to a method for preparing various dibenzo-crown ethers (DBC) including both of the symmetric and asymmetric atom ring structures. In the present invention, methods for preparing DBC using organic synthesis by using two microwaves are disclosed in which one is a preparation method using appropriate dihalide and one-port equimolar reaction of a base and catechol for preparing symmetrical DBC, and the other one is a preparation method using diphenol intermediates for preparing symmetrical or asymmetrical DBC. According to the present preparation method, the preparation of DCB can be done within 60 minutes, which were taken at least one day with a conventional method, and the yield of DBC can be improved than before.

Composite membranes with surface-modifying macromolecules for halogenated hydrocarbons removal from water in membrane extraction process

AbstractFlat sheet composite polysulfone (PSf) membranes blended with surface-modifying macromolecules (SMM) were prepared, characterized, and tested for halogenated hydrocarbons (HHC) (i.e. trichloroethylene, TCE) permeation and separation from water in an extractive membrane system. The fluorine end groups in SMMs facilitated its migration towards the membrane surface during membrane casting, whereas the polydimethylsiloxane component rendered the SMM organophilic which improved the surface affinity of the composite membrane towards TCE. Polydimethylsiloxane content in SMM, SMM content in PSf, and air-exposure of the casted blend solutions before membrane formation were found critical in obtaining an effective composite membrane. The presence of a selective SMM layer on the membrane surface was confirmed via contact angle measurement, Fourier-transform infrared spectrometry analysis, and field emission-scanning electron microscope. The most effective composite membrane (PSf with 15 wt% H-SMM and air exp...