Adsorption Of Naphthenic Acids Research Articles

Competitive adsorption between sodium citrate and naphthenic acids on alumina surfaces: Experimental and computational study

The adsorption of naphthenic acids (NAs) on clay surfaces induces an increase in surface hydrophobicity, which is detrimental to crude oil recovery and froth quality. Sodium citrate (Na3Cit), with more functional groups than NAs, is expected to compete with NAs for adsorption on mineral surfaces. The adsorption of NAs on alumina surfaces was quantified in the presence and absence of Na3Cit at pH 8 ± 0.1. An increase in hydrophobicity of the alumina surface was observed after the adsorption of NAs without Na3Cit. However, adding Na3Cit significantly reduced NAs adsorption and protected the surface wettability. The viscoelasticity and electrokinetic properties of adsorbed materials indicate Na3Cit was preferentially covered on alumina surfaces and repelled NAs by its negative charges. The competition between Na3Cit and NAs for adsorption sites was explained using ab initio Car-Parrinello molecular dynamics (CPMD) simulation and periodic plane-wave density functional theory (DFT) to calculate inner-sphere adsorption and outer-sphere adsorption, respectively. Favourable adsorption of sodium citrate than NAs representatives on aluminum (hydr)oxide cluster and the basal and edge planes of gibbsite were observed from the perspective of free energy barrier and adsorption energy, respectively.

Sludge-based activated biochar for adsorption treatment of real oil sands process water: Selectivity of naphthenic acids, reusability of spent biochar, leaching potential, and acute toxicity removal

Large volumes of oil sands process water (OSPW) containing naphthenic acids (NAs) and other contaminants are generated by oil sands operations. For the first time, pristine and zinc chloride-activated biochars from sludge from a municipal wastewater treatment plant are studied in the adsorption of NAs in real OSPW. By using activated biochar instead of pristine biochar, the adsorption capacity (qt) for total NAs (classical and oxidized NAs) increased from 2.3 to 26.6 mg/g. The increase in qt for activated biochar was related to the improvement of surface area from 7.9 to 513 m2/g, the abundance of mesopores (89% of pore volume), and the oxygen-containing surface groups. Equilibrium was reached at 2 h of contact time. Considering the thousands of structures of NAs in the OSPW, the activated biochar presented higher affinity for NAs with higher carbon and double bond equivalency numbers, therefore, NAs with more hydrophobic and higher cyclicity characteristics. Pore-filling, hydrogen bonding, and π-π interactions are the adsorption mechanisms. Thermal regeneration of spent activated biochar was studied, and in the fifth cycle of regeneration, the regenerated biochar had qt of 7.1 mg/g, which was 5 times higher than the adsorption capacity of fresh pristine biochar. Adsorption treatment of OSPW using activated biochar decreased the following parameters: metals Mg (7%), Ca (21%), Sr (27%), and Ba (60%), organic matter by means of DOC (63%) and COD (66%), acute toxicity towards V. fischeri (66%) and bioavailability of organics (91%). These findings promote circular economy as it presents an efficient adsorbent for NAs in OSPW developed from sludge, reducing the environmental impact associated with sludge disposal and allowing the efficient reclamation and reuse of OSPW.

Application of mesoporous zeolite Socony Mobil-5 (ZSM-5) as an adsorbent material for the removal of naphthenic acid present in oil-produced water

The porous structure of ZSM-5 zeolite strongly affects the adsorption, especially when resistant compounds are present in the water, such as naphthenic acid in oil-produced water. In this sense, ME-ZSM-5 zeolite was synthesized by adding sodium alginate for later use as an adsorbent to remove naphthenic acid from synthetic water and real oil-produced water. Firstly, the results showed that the structural characteristics of the modified zeolite were improved by using sodium alginate (surface area of 235.58 m2 g−1 and total pore volume of 0.125 cm3 g−1). Besides, the adsorption of naphthenic acid from synthetic water was optimal using an adsorbent dosage of 3 g L−1 and pH 4, being the adsorption capacity of 195 mg g−1. Still, in synthetic solutions, the enthalpy of adsorption confirmed an exothermic process, and kinetic studies showed that the system reached equilibrium within the first 50 min. Finally, ME-ZSM-5 was applied to remove naphthenic acid from a real sample of oil-produced water and removed 92%. Therefore, ME-ZSM-5 zeolite was successfully synthesized and could be used as adsorbent material to uptake naphthenic acid from oil-produced water.

The cooperative effect between cyclic naphthenic acids and surfactant enhances the separation efficiency

Naphthenic Acids (NAs) are responsible for corrosion, produced water pollution, and are toxic to marine life. Therefore, more efficient NAs extraction techniques, such Micellar-Enhanced Ultrafiltration (MEUF), have been developed. In this work, Molecular Dynamics simulations were employed to deepen the comprehension of the behavior and properties of NA in interfacial systems and micellar systems. The calculated distribution coefficient (log D) in different water/oil interfaces demonstrated the greater affinity between NA and cyclic structures, showing a more negative free energy in the systems with toluene. Furthermore, simulations with different NAs and surfactant showed that micelle is effective in NAs carriage by two different interaction conformations, both by intercalation and adsorption of NAs on micelle surfaces, guiding to a micelle increase of about 5%. Radial distribution, hydrogen-bond, and non-bonded analysis indicated that NAs affect interactions between surfactant molecules' by diminishing the Lennard-Jones contribution. Moreover, the incorporated alicyclic molecules are responsible for facilitating the absorption of more NAs by the micelle. So, to enhance NAs separation from oil or produced water, cyclic molecular systems may be employed.

Adsorption of naphthenic acids from oil sand process‐affected water with water‐insoluble poly(β‐cyclodextrin‐citric acid)

AbstractWith polyvinyl alcohol as the main chain, a water‐insoluble poly(β‐cyclodextrin‐citric acid) was prepared as a supramolecular adsorbent for the treatment of oil sand process‐affected water (OSPW) containing naphthenic acids (NAs). FT‐IR, TGA, and SEM were used for the characterization of adsorbent, and an automatic infrared oil analyzer was used to monitor the concentration change of NAs in the water. The adsorption behaviour and mechanism were explored by adsorption kinetics and thermodynamic studies. The results showed that the adsorption process could be described well with the Langmuir isothermal adsorption model and quasi‐second‐order kinetic model, which indicated that the host‐guest interaction of β‐cyclodextrin promoted the adsorption of NAs. The discussion regarding pH indicated that the neutral condition (pH = 7) was considered the best. In addition, a molecular dynamics simulation was carried out using a Materials Studio package purchased from Accelrys to verify that the structure with polyvinyl alcohol as main chain was beneficial to adsorption. The excellent adsorption capacity (qmax was 193.42 mg · g−1) and reusability of the poly(β‐cyclodextrin‐citric acid) indicated its potential as practical adsorbent for the treatment of OSPW.

Adsorption of naphthenic acid on magnetite at different temperatures

Isotherms of naphthenic acid adsorption from heptane solutions on highly dispersed magnetite are studied using the adsorption equilibrium approach. The isosteric heats of naphthenic acid adsorption from heptane solutions are calculated over a temperature range of 293–308 K. The adsorption isotherms can be approximated using the equation for a straight line. Experimental adsorption isotherms are shown to be linear in the coordinates of the equation for the theory of volume filling of micropores (TVFM).

Impact of polymeric membrane filtration of oil sands process water on organic compounds quantification

The interaction between organic fractions in oil sands process-affected water (OSPW) and three polymeric membranes with varying hydrophilicity (nylon, polyvinylidene fluoride and polytetrafluoroethylene) at different pHs was studied to evaluate the impact of filtration on the quantification of acid-extractable fraction (AEF) and naphthenic acids (NAs). Four functional groups predominated in OSPW (amine, phosphoryl, carboxyl and hydroxyl) as indicated by the linear programming method. The nylon membranes were the most hydrophilic and exhibited the lowest AEF removal at pH of 8.7. However, the adsorption of AEF on the membranes increased as the pH of OSPW decreased due to hydrophobic interactions between the membrane surfaces and the protonated molecules. The use of ultra pressure liquid chromatography-high resolution mass spectrometry (UPLC/HRMS) showed insignificant adsorption of NAs on the tested membranes at pH 8.7. However, 26±2.4% adsorption of NAs was observed at pH 5.3 following the protonation of NAs species. For the nylon membrane, excessive carboxylic acids in the commercial NAs caused the formation of negatively charged assisted hydrogen bonds, resulting in increased adsorption at pH 8.2 (25%) as compared to OSPW (0%). The use of membranes for filtration of soluble compounds from complex oily wastewaters before quantification analysis of AEF and NAs should be examined prior to application.

Adsorption of naphthenic acids on high surface area activated carbons

In oil sands mining extraction, water is an essential component; however, the processed water becomes contaminated through contact with the bitumen at high temperature, and a portion of it cannot be recycled and ends up in tailing ponds. The removal of naphthenic acids (NAs) from tailing pond water is crucial, as they are corrosive and toxic and provide a substrate for microbial activity that can give rise to methane, which is a potent greenhouse gas. In this study, the conversion of sawdust into an activated carbon (AC) that could be used to remove NAs from tailings water was studied. After producing biochar from sawdust by a slow‐pyrolysis process, the biochar was physically activated using carbon dioxide (CO2) over a range of temperatures or prior to producing biochar, and the sawdust was chemically activated using phosphoric acid (H3PO4). The physically activated carbon had a lower surface area per gram than the chemically activated carbon. The physically produced ACs had a lower surface area per gram than chemically produced AC. In the adsorption tests with NAs, up to 35 mg of NAs was removed from the water per gram of AC. The chemically treated ACs showed better uptake, which can be attributed to its higher surface area and increased mesopore size when compared with the physically treated AC. Both the chemically produced and physically produced AC provided better uptake than the commercially AC.

Adsorption of Naphthenic Acids onto Mineral Surfaces Studied by Quartz Crystal Microbalance with Dissipation Monitoring (QCM-D)

In the present research, the adsorption of naphthenic acids from n-dodecane solutions onto hydrophilic surfaces of the most common minerals in petroleum reservoirs (silica, alumina, and calcite) ha...

Adsorptive recovery of naphthenic acids using ion-exchange resins

Adsorption of naphthenic acids has been studied on commercial weak and strong anion-exchange resins. The capacity and equilibrium constant of adsorption on these resins are compared with those obtained with zeolites, bentonite and polyvinyl pyridine. Macroporous weakly anionic ion-exchange resins with weak tertiary amine group have good adsorption capacity for the removal of naphthenic acids from petroleum oil as compared to strong anion-exchange resins with isoporous structure although the strong anion-exchange resin shows greater interaction with naphthenic acids. The rate of uptake of naphthenic acid is governed by the internal diffusional resistance which is also dependent on adsorbed phase concentration.