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Discharging water from oilfields has become one of the major environmental issues related to the oil industry. This work presents a study on the adsorption of oil onto nanoparticles of hydrophobic silica and silica nanoparticles functionalized with a petroleum vacuum residue (VR) at 2 and 4 wt% to reduce the amount of oil in oil–brine and oil–water emulsions at different pH values (5, 7 and 9). The initial concentration of crude oil in water ranged from 500 to 1500 mg/l. The change in oil concentration after adsorption was determined using a UV–VIS spectrophotometer. Experimental data on the adsorption kinetics were fitted to pseudo-first-order and pseudo-second-order models, with better results being obtained for the latter. Results of the study showed 100% oil removal for all the systems studied and a better performance was achieved for oil-saltwater emulsions than the experiments performed using oil-saltwater emulsions. In addition, the adsorption equilibrium was achieved faster for the oil–water emulsion using the salty medium. Adsorption velocity was higher for neutral and basic systems compared with acid ones, and it was improved by increasing the amount of VR on silica surface.

At the request of the Publisher, the following article has been retracted for redundant publication. Taborda EA, Franco CA, Ruiz AM, Alvarado V, Cortés FB (2017) Striking behavior of the rheology in heavy crude oils by adding nanoparticles. Adsorption Science & Technology . Epub ahead of print 29 August 2017. DOI: 10.1177/0263617417727996 . After publication, the Adsorption Science & Technology Editorial Office became aware that this article had been simultaneously submitted to Adsorption Science & Technology, and two other journals: Chemical Engineering Communications and Energy Fuels , which resulted in the redundant publication of the above article. The above article is near-identical to the following articles published by the same group of authors in Chemical Engineering Communications and Energy & Fuels. Taborda EA, Franco CA, Ruiz AM, Alvarado V, Cortés FB (2017) Anomalous Heavy-Oil Rheological Thinning Behavior upon Addition of Nanoparticles: Departure from Einstein’s Theory. Chemical Engineering Communications 204(6): 648–657. Taborda EA, Franco CA, Ruiz AM, Alvarado V, Cortés FB (2017) Experimental and Theoretical Study of Viscosity Reduction in Heavy Crude Oils by Addition of Nanoparticles. Energy Fuels 31(2): 1329–1338.

The main objective of this work is to synthesize and evaluate magnetite (Fe 3 O 4 ) nanoparticle-based ferrofluids for reducing the viscosity of an extra heavy crude oil. The carrier fluid of the nanoparticles was synthesized using an engine lubricant recycled from the automotive industry and hexadecyltrimethylammonium bromide as a surfactant. Fe 3 O 4 nanoparticles were synthesized by coprecipitation method. The effect of the concentration of nanoparticles in the viscosity reduction degree was determined for dosages between 0 and 50,000 mg/L. Different dosages of carrier fluid were evaluated between 0 and 10% v/v. The effects of the amount of brine emulsified, temperature, time, and shear rate were assessed. Overall, the results showed that viscosity and shear stress of extra heavy crude oil could be reduced up to 81 and 78% in the presence of ferrofluid, respectively. The rheological behavior of extra heavy crude oil in the presence and absence of ferrofluid was assessed by Cross, Ostwald-de Waele, and Herschel-Bulkley models.