Enhancing Oil Removal from Water using Ferric Oxide Nanoparticles Doped Carbon Nanotubes Adsorbents

Oil contaminated water is one of the challenges in water resources management. It is crucial to remove the oil droplets from water in order to meet the discharge regulations set by the environmental authorities. Carbon nanotubes (CNTs) have generated a lot of attention as a new type of adsorbent due to their exceptionally high adsorption capacity for oil–water separation. The high hydrophobicity of CNTs makes them good candidates to enhance the de-oiling process from wastewater. In this study, we have reported the synthesis and evaluation of novel iron-oxide/CNTs nanocomposites for oil–water separation. The CNTs were doped with different loadings of iron oxide nanoparticles using a wet impregnation technique. The synthesized nanocomposite nanomaterials were characterized using field emission scanning electron microscopy (FE-SEM), high resolution transmission electron microscopy (TEM), Brunauer, Emmett and Teller (BET) technique, X-ray diffraction (XRD), and thermogravimetric analysis (TGA). The effect of adsorption parameters, including, adsorbent dosage, contact time, and agitation speed on the oil removal efficiency were optimized using batch experiments. The sorption capacities of doped CNTs were found to be greater than 7 g/g for gasoline oil. The doped CNTs reached maximum sorption capacity after only 15 min providing one of the fastest minimum contact times reported of all oil sorbent materials. The loading of Fe2O3 nanoparticles on the negative surface of CNT decreases the negative sign and magnitude of the zeta potential by overcoming the repulsive effects of the electrical double layers to allow the finely sized oil droplets to form larger droplets through coalescence. Therefore increasing percentage of the Fe2O3 on the surface of CNT increased the removal of the emulsified oil from the water

Impact of combined oil-in-water emulsions and particulate suspensions on ceramic membrane fouling and permeability recovery

The application of crossflow ceramic microfiltration (CFCMF) to the removal of emulsified oil from a simple analogue of raw produced water (PW) arising from oil exploration has been studied. Outcomes relate to surfactant-stabilised oil-in-water (o/w) emulsions both as a discrete emulsion and in combination with a colloidal suspension of particulate solids (bentonite). The impact on both fouling during the filtration cycle and residual fouling of the ZrO2-TiO2 membrane, following aggressive caustic-acid chemical cleaning applied between six sequential 30-min filtration runs, was investigated. Results showed the addition of suspended solids to the o/w emulsion to be extremely deleterious to sustaining both the permeability and selectivity of the membrane. The addition of 1500 mg·L−1 of bentonite to a 10 vol.% emulsion resulted in a permeability decrease of 3.5–5 times over that recorded for the emulsion, and 8–36 times lower than that of the bentonite suspension. Oil passage through the microfiltration membrane (0.45 μm pore size) was concomitantly increased six-fold. Tests performed to assess the cleanability of the membrane demonstrated similar differences between the three feed liquids. The permanent fouling of the membrane by the combined emulsion/suspension reduced its permeability by a factor of 16 over that attained for the emulsion-fouled membrane, or 25 times less than the residual permeability of the membrane challenged with the suspended particles. Moreover, the residual permeability of the emulsion/suspension-fouled membrane was still in decline following the sixth run. The results emphasise the importance of considering possible particle-emulsion interactions in studying membrane filtration of PW analogues.Scopu

Evaluation of the current state and perspective of wastewater treatment and reuse in Qatar

In Qatar, many freshwater resources have already been depleted due to the overconsumption as a result of the population and economic growth. Moreover, due to the lack of sufficient sewage treatment infrastructure, Qatar is facing a daily problem in treating the wastewater. Dumping untreated sewage effluents (SE) contaminates groundwater resources and worsens the current water status in the country. On the other hand, treated SE (TSE), which is estimated at about 0.75 million m3/d, could be one of the main sources of fresh water which can be used in agriculture and industry and even as a source of drinking water in Qatar. Qatar uses only about 27% of TSE in growing fodder (25 million m3/y) and landscape irrigation (1 million m3/y) while about 73% of the total TSE is discharged to septic lagoons to dry or percolate into groundwater (70 million m3/y) and runoff (0.5 million m3/y). Qatar can better utilize its TSE in several applications by further treating the produced TSE. In this paper, a review on the current state and a perspective into the wastewater treatment and reuse in Qatar is presented. Moreover, the main aspects, which should be considered while making a decision on reusing the treated SE in Qatar, are also addressed.Scopu

Enhanced Adsorption of Selenium Ions from Aqueous Solution Using Iron Oxide Impregnated Carbon Nanotubes

The aim of this research was to investigate the potential of raw and iron oxide impregnated carbon nanotubes (CNTs) as adsorbents for the removal of selenium (Se) ions from wastewater. The original and modified CNTs with different loadings of Fe2O3 nanoparticles were characterized using high resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM), X-ray diffractometer (XRD), Brunauer, Emmett, and Teller (BET) surface area analyzer, thermogravimetric analysis (TGA), zeta potential, and energy dispersive X-ray spectroscopy (EDS). The adsorption parameters of the selenium ions from water using raw CNTs and iron oxide impregnated carbon nanotubes (CNT-Fe2O3) were optimized. Total removal of 1 ppm Se ions from water was achieved when 25 mg of CNTs impregnated with 20 wt.% of iron oxide nanoparticles is used. Freundlich and Langmuir isotherm models were used to study the nature of the adsorption process. Pseudo-first and pseudo-second-order models were employed to study the kinetics of selenium ions adsorption onto the surface of iron oxide impregnated CNTs. Maximum adsorption capacity of the Fe2O3 impregnated CNTs, predicted by Langmuir isotherm model, was found to be 111 mg/g. This new finding might revolutionize the adsorption treatment process and application by introducing a new type of nanoadsorbent that has super adsorption capacity towards Se ions.Scopu

Synoptic analysis of direct contact membrane distillation performance in Qatar: A case study

The aim of this study is to evaluate a bench scale direct contact membrane distillation (DCMD) performance using flat sheet polytetrafluoroethylene (PTFE) membrane at different inlet flow rates, temperatures, and salinity composition. The effect of the various operating conditions on the quality of the distillate water produced was investigated by Inductively Coupled Plasma/Optical Emission Spectrometry (ICP/OES) and ion chromatography (IC). Five different feed solutions were studied such as the Arabian Gulf seawater, rejected brine from Qatari thermal desalination plants and artificial brine. A permeate flux of 35.6 LMH can be produced at temperature difference of 50. C between hot and cold sides. The thermal energy efficiency of the system was analyzed and reached up to 22%. The flow mode and turbulence promoter in feed channels were found to have a very important effect on the flux and energy efficiency. It was also noted that using spacers in the flow channels increase the distillate flux by more than 51% as compared with a spacer-free system. The investigation has shown that the highest Gain Output Ratio (GOR) value can be obtained when using less saline feed solution at the highest feed temperature, lowest permeate temperature and lowest flow rate. Finally, the salt rejection rate throughout the conducted tests was very high (>. 99.9%) and almost independent of any studied operational parameters. Eventually, DCMD has proven to be a feasible and effective technology capable of consistently producing high quality distillate from a very high salinity feed even with substantial quality difference compared to other desalination methods such as RO and MSF.Scopu

Reducing Flux Decline and Fouling of direct Contact Membrane Distillation by Utilizing Thermal Brine from MSF Desalination Plant

Fouling and scaling is one of the major challenges in membrane distillation process. This study investigates the utilizing of thermal rejected brine produced from multi-stage flash distillation (MSF) to minimize fouling and scaling on membranes in direct contact membrane distillation (DCMD) settings. The effect of operating parameters on permeate flux and the extent of scaling during long time operation was considered and compared when real seawater and reject thermal brine were used. The deposit morphology of scaling was observed using different analytical methods, including scanning electron microscopy and contact angle measurement. Thermal brine showed enhanced performance in terms of flux and scaling compared to seawater. It was found that flux is reduced by 8% compared to 12-20% when the feed to the DCMD was brine was used as compared to seawater. In addition, thermal brine feed showed better anti-fouling behavior compared to the fresh seawater which contains different organic and inorganic contaminants.Furthermore, utilizing waste heat contained in the thermal brine to raise the temperature of the feed was advantageous in increasing the energy efficiency of DCMD process.The authors would like to express their gratitude to Qatar University and ConocoPhillips GWSC for their financial support of this work under grants QUST-CENG Fall 12/13-22 and QUEX-CWT-11/12-5 respectively