Static Adsorption Research Articles

Recovery and separation of glycyrrhizic acid from Natural Deep Eutectic Solvent (NADES) extract by macroporous resin: adsorption kinetics and isotherm studies

Natural Deep Eutectic Solvents (NADESs) have emerged as a green and sustainable alternative to conventional organic solvents to extract bioactive compounds. However, the recovery of bioactive compounds from the NADES extracts is challenging, restricting their large-scale applications. The present work investigated the recovery of glycyrrhizic acid (GA) from choline-chloride/lactic acid NADES extract using macroporous resins. GA possesses a wide spectrum of biological activities, and it is extracted from the well-known herb Glycyrrhiza glabra. During resin screening, DIAIONTM SP700 showed high adsorption and desorption capacities. The adsorption kinetics study demonstrated that the adsorption of GA on SP700 followed Pseudo First-order kinetic model. Moreover, the adsorption behaviors were elucidated by the Freundlich isotherm using a correlation coefficient based on a static adsorption study at different temperatures and pH. Furthermore, the thermodynamic parameters, for instance, the change of Gibbs free energy (ΔG*), entropy (ΔS*), and enthalpy (ΔH*), showed that the adsorption process was spontaneous, favorable and exothermic. In addition, the sample after macroporous resin treatment, which is enriched with GA exhibited good anticancer potential analyzed by SRB assay. The regenerated NADES solvent was recycled twice, keeping more than 90% extraction efficiency, indicating good reusability of NADES in the GA extraction process by using macroporous resin.

Pt(IV)-ion imprinted ordered mesoporous organosilica for platinum preconcentration prior to electrothermal atomic absorption spectrometry determination in geological samples

Pt(IV) ion-imprinted thiocyanato-functionalized SBA-15 material (Pt(IV)S1) was proposed for preconcentration of Pt(IV) ions from digested geological samples before its electrothermal atomic absorption spectrometry (ETAAS) determination. The ion-imprinted material exhibited very good adsorption affinity towards Pt(IV) ions. Under the optimal pH (pH = 3) the maximum static adsorption capacity for Pt(IV) was equal to 175 mg g−1. The use of Pt(IV)S1 as an adsorbent allowed for the quantitative adsorption of Pt(IV) ions from solutions with concentrations up to 25 mg L−1. The creation of ion imprinted adsorption centres resulted in an increase of the adsorption rate and selectivity towards Pt(IV) compared to the similar non-ion imprinted material. The analytical procedure was based on the adsorption of Pt(IV) ions and dissolution of the Pt-loaded sorbent in a small volume of hydrofluoric acid before its dilution with 5% hydrochloric acid and introduction into an electrothermal atomizer. The enrichment factor of the proposed procedure was 38, while the limit of quantification was 0.079 mg kg−1.

Adsorption Behavior and Adsorption Dynamics of Micrometer-Sized Polymer Microspheres on the Surface of Quartz Sand

The adsorption of polymer microspheres in a stratum can directly affect its action mode and performance in the actual application process. Understanding the adsorption pattern of polymer microspheres and their adsorption mechanism can facilitate optimization of the application mode and enhance the use efficiency. Ultraviolet spectrophotometry was employed to measure the static adsorption characteristics of polymer microspheres (PMS) on the surface of quartz sand. The PMS adsorption capacity on the surface of quartz sand increased with increasing concentration. When the concentration was 1000 mg/L, the static equilibrium adsorption capacity was 402 μg/g, and monolayer adsorption was dominant. The effect of the contact time on the adsorption was investigated, and the fitting was performed using the isothermal adsorption thermodynamic equilibrium model and the adsorption kinetic model. The adsorption of 800 mg/L PMS tended to equilibrate after 0.8 h of adsorption on the surface of quartz sand, and the adsorption of 1400 mg/L PMS tended to equilibrate after 1 h of adsorption on the surface of quartz sand. Good fitting results of the kinetic adsorption process were obtained using the pseudo-first-order (PFO) model, pseudo-second-order (PSO) model, Elovich model, and mixed-order (MO) model. The effects of the temperature, particle size of the quartz sand, solid–liquid ratio, and salinity on the adsorption of PMS on the surface of quartz sand were examined. The PMS adsorption capacity on the surface of quartz sand decreased with increasing environmental temperature. The adsorption of PMS at the solid–liquid interface was an exothermic process, and the enthalpy of adsorption was negative. As the mass of the quartz sand in the solid–liquid ratio increased, the adsorption capacity decreased; a low salinity and neutral pH were conducive to the adsorption of PMS on the surface of quartz sand.

Efficient removal of perfluorobutanesulfonic acid from water through a chitosan/polyethyleneimine xerogel

Due to the recently ratified legislations, the use of long-chain poly- and perfluoroalkyl substances (PFASs) must be reduced and in the absence of a safe alternative, short-chain PFASs are currently used in their place. The continuously growing utilization of the short-chain PFASs, results in their abrupt introduction in the environment, and highlights the importance of adopting efficient remediation strategies. This study addresses an appropriate solution to remove perfluorobutanesulfonic acid (PFBS) from aqueous media through a static adsorption process. Specifically, a chitosan/polyethyleneimine based composite xerogel was prepared and its ability to remove PFBS from water was studied in detail. Behavioral patterns of the PFBS adsorption process were perused over a broad range of concentrations from ppb to ppm, and the adsorption studies reveal that the maximum PFBS adsorption capacity reaches up to 305 mg/g within 24 h from the beginning of the process. In addition to the electrostatic interaction between the amine groups of the xerogels and the negatively charged PFBS molecules, the formation of hydrogen bonds were also revealed by the chemical characterization and confirmed by molecular dynamics simulation studies.

Selective capture of palladium by protonation-armed pyridine nitrogen in extreme water environments

Due to the hostile environment in which it is recovered, selective separation of palladium from the leachate of spent catalysts containing palladium is of considerable utility but faces substantial obstacles. This work designed and synthesized a bipyridine-based porous organic polymer (POP-BPy) via free radical polymerization. Meanwhile, its adsorption characteristics and the mechanism of adsorption in extreme environments were examined. In hostile conditions, the resultant POP-BPy display exceptional mechanical stability and environmental resistance. Impressively, POP-BPy has an excellent adsorption capacity of Pd(II) (248 mg/g) in harsh environments (aqua regia: AR; half-diluted aqua regia: AR“1 + 1”), and also had superior selectivity and rapid kinetics. The selectivity of POP-BPy for Pd(II) was verified in combination with relevant experiments (βPd(II)/Pt(II) = 36.19, βPd(II)/Pt(II) = 23.90). Furthermore, combining density functional theory (DFT) and molecular dynamics (MD) simulations, the mechanism of selectivity of POP-BPy for Pd(II) was revealed from static adsorption sites to dynamic adsorption processes in a holistic manner, which attributed to the strong attraction of protonated pyridine nitrogen to PdCl42- and site suitability. Furthermore, the application of POP-BPy to spent catalyst recovery resulted in up to 100% removal of Pd(II) from the actual leaching solution, and fixed bed column experiments can effectively treat 2688 bed volumes (L) of feed streams (10 mg/L) before reaching the breakthrough point (<1 mg/L). Overall, this work has opened up new avenues for the selective recycling of valuable metals in harsh environments.

Efficient adsorption of alginate oligosaccharides by ion exchange resin based on molecular simulation and experiments

Alginate oligosaccharides (AOS) with low polymerization have gained considerable attention due to their unique physiological activities. However, the lack of understanding regarding the mechanism of action for resin selection and optimization of separation processes has impeded their precise chromatographic separation and large-scale production. Here, the adsorption–desorption characteristics of AOS on the resins with varying solid phase composition, including backbones, functional groups, crosslinking degrees, and counterions resin structures, were analyzed using simulations and experiments. The simulation results revealed that the structural differences of AOS are characterized by their electrostatic potential and lowest unoccupied molecular orbital energy level. Based on molecular simulations, we predicted that the basic anion resin with a styrene backbone would be suitable for AOS separation. Subsequently, we constructed SM-7Cl resin based on the simulation results and performed static adsorption experiments to verify the prediction. SM-7Cl resin demonstrated noteworthy adsorption–desorption performance for AOS, with an adsorption capacity of 471.2 mg/g and a desorption rate of 89.45%. The fitting adsorption isotherm was consistent with the Freundlich model, indicating that the adsorption proceeded spontaneously. The equilibrium times for AOS adsorption on the gel-type resin and the macroporous resin, which both followed a pseudo-second-order kinetic model, were 30 min and 60 min, respectively. This study provides optimized chromatographic media and separation processing that can be implemented for the amplification of chromatographic separation in AOS production.

Polymer Screening for Efficient Water Cut Reduction in a Sandstone Oilfield in Kazakhstan.

Polymer flooding is one of the most widely used and effective enhanced oil recovery techniques. It can improve the macroscopic sweep efficiency of a reservoir by controlling the fractional flow of water. The applicability of polymer flooding for one of the sandstone fields in Kazakhstan was evaluated in this study and polymer screening was carried out to choose the most appropriate polymer among four hydrolyzed polyacrylamide polymer samples. Polymer samples were prepared in Caspian seawater (CSW) and assessed based on rheology, thermal stability, sensitivity to non-ionic materials and oxygen, and static adsorption. All the tests were performed at a reservoir temperature of 63 °C. Based on the results of the screening study, tolerance of a polymer towards high-temperature reservoir conditions, resistance to bacterial activity and dissolved oxygen present in make-up brine, chemical degradation, and reduced adsorption on rock surface were considered the most important screening parameters. As a result of this screening study, one out of four polymers was selected for the target field as it showed a negligible effect of bacterial activity on thermal stability. The results of static adsorption also showed 13-14% lower adsorption of the selected polymer compared to other polymers tested in the study. The results of this study demonstrate important screening criteria to be followed during polymer selection for an oilfield as the polymer should be selected based on not only polymer characteristics but also the polymer interactions with the ionic and non-ionic components of the make-up brine.

Selective separation of dye/salt mixture using diatomite-based sandwich-like membrane

A novel nanofiltration membrane was developed by entrapping a layer of modified diatomaceous earth between two layers of electrospun polysulfone (E-PSf) nanofibers. The diatomaceous earth particles and the fabricated membrane were characterized using FTIR, SEM, EDS, zeta potential, and water contact angle techniques. The static adsorption and dynamic separation of pristine E-PSF and sandwich-like membranes for methylene blue (MB) with/without salt were investigated under different operating conditions. The Langmuir model suited the MB adsorption isotherm data with a linear regression correlation coefficient (R2) >0.9955. As pH increased, both flux and MB rejection of the sandwich-like membrane improved by up to 183.8 LMH and 99.7%, respectively, when operated under gravity. The water flux of the sandwich-like membrane was sharply increased by increasing the pressure up to 19,518.2 LMH at 4.0 bar. However, this came at the expense of MB rejection (10.93%) and reduced its practical impact. At a high salt concentration, the sandwich-like membrane also indicated remarkable dye/salt separation with a higher permeation of salt (<0.2% NaCl rejection) and MB rejection (>99%). The performance of the regenerated diatomaceous material and membrane was maintained during five cycles of operation compared to that of the original ones.

Extractive adsorption of 1,3-propanediol on a novel polystyrene macroporous resin enclosing medium and long-chain alcohols as extractant

Extractive adsorption is an integrated separation method employing a novel resin with both particle and liquid characteristics in terms of adsorption and extraction. In this study, the novel extractive adsorption polystyrene-divinylbenzene (PS-DVB) macroporous resin was synthesized by suspension polymerization, in which n-octanol (OL-PS-DVB) or mixed alcohols of n-octanol, undecyl alcohol, and tetradecyl alcohol (MA-PS-DVB) were added as porogen and enclosed in the resin skeleton after the reaction. The characterization of the two novel resins of OL-PS-DVB and MA-PS-DVB showed that they have large specific surface areas of 48.7 and 17.4 m2/g, respectively. Additionally, the two synthesized resins have much higher static adsorption capacities of 1,3-propanediol (511 and 473 mg/g) and dynamic adsorption capacities (312 and 267 mg/g) than traditional resins, because extractants enclosed in the resin can increase the adsorption capacity. Through Langmuir equation, the theoretical static maximum adsorption capacity of the mixed alcohols resin is 515 mg/g at 298 K and Gibbs free energy change of adsorption was -3781 J/mol, indicating that the adsorption process was spontaneous. In addition, the sorbent concentration effect in the resin was generated at high 1,3-propanediol (1,3-PDO) concentrations. The fitting of the Flocculation model can reveal that there is a possible relation between adsorption and flocculation. Compared to OL-PS-DVB, MA-PS-DVB showed better performance in the recovery yield of 1,3-PDO and other byproducts, the removal rates of the inorganic salt and protein, and the efficiency of recycled resin. For MA-PS-DVB, the recovery of 1,3-PDO, butyrate acid, acetic acid, and residual glycerol was 97.1%, 94.7%, 93.3%, and 90.3%, respectively. Simultaneously, the resin of MA-PS-DVB could remove 93.8% of inorganic salts and 90.9% of proteins in the concentrated fermentation broth. The two synthesized resins of OL-PS-DVB and MA-PS-DVB still had 90% or 92% of capacity for extractive adsorption of 1,3-propanediol after 10 times of recycling, which exhibited potential application in the separation of 1,3-propanediol from fermentation broth.

Construction of mesoporous Si-Fe-GO composite for the highly efficient removal of uranium

The mesoporous Si-Fe-GO composite was prepared by sol–gel method to remove uranium. In the static adsorption process, the Si-Fe-GO composite possessed strong uranium-chelating ability with fast uranium adsorption kinetic (120 min) and high uranium adsorption capacity (576.4 mg/g). The adsorption behavior perfectly followed the pseudo-second-order kinetic and Langmuir isotherm models, revealing the nature of monolayer chemical adsorption. The tolerance experiments of coexisting ions showed that the Si-Fe-GO composite possessed a strong affinity for uranium, which was beneficial for the enrichment of uranium in a multi-component wastewater system. The good regeneration ability also reflected the practical application value of the Si-Fe-GO composite. Besides, the dynamic adsorption studies showed that the Si-Fe-GO composite might be suitable for the remediation of uranium-containing wastewater with low flow rate and low uranium concentration. In conclusion, this work would contribute to the development of functional SiO2 materials for water remediation and meet the practical requirements for the cleanup of uranium from wastewater.

In-situ conversion of geopolymer into novel floral magnetic sodalite microspheres for efficient removal of Cd(II) from water

In the present work, a novel, floral-like, magnetic sodalite microsphere (SODM) was synthesized in situ by using fly ash (FA) and metakaolin (MK) as raw materials and was used to remove Cd(II) from water. Its magnetism can solve the problems of adsorbent recovery and possible secondary pollution. During the static adsorption, SODM shows a maximum adsorption capacity of 245.17 mg/g. The adsorption of Cd(II) on the SODM surface is spontaneous, exothermic, and physicochemical adsorption, which was evaluated by thermodynamics, kinetics, and isotherm studies. During dynamic adsorption, SODM shows a maximum adsorption capacity of 342.74 mg/g in the simulated solution prepared by the deionized water, compared to 215.88 mg/g in the simulated solution prepared using Xiangsi Lake water from Guangxi Minzu University. At 0.5 g SODM dosage in the dynamic adsorption, the adsorption capacity could rise to 632.81 mg/g. These results demonstrated the excellent Cd (II) adsorption performance of the SODM. The adsorption of cadmium on the SODM surface includes the synergistic effects of electrostatic attraction, ion exchange, and surface coordination reaction. Besides, the SODM shows good regeneration performance in both the deionized water and Xiangsi Lake water. The present study explores SODM as an adsorbent for the Cd (II) removal from wastewater and unbolts the industrial applicability of the SODM in the field of wastewater purification.

Preparation of a functional fracturing fluid with temperature- and salt-resistance, and low damage using a double crosslinking network

Fracturing fluids (FFs) have been widely used to stimulate the tight reservoir. However, current FFs will not only lose their rheological property at high temperatures and high salt but also show an incomplete gel-breaking property. Herein, a double crosslinking network FF with pretty superiorities in rheology and low damage to the core was constructed by introducing both physical crosslinking and chemical crosslinking into the system. The construction of double crosslinking networks enhanced the rheology of this functional FF. The particle sizes of gel-breaking fluids are mainly distributed in 1.0–10,000 nm; furthermore, for every 10,000 mg/L increase in salinity, the particle size of the gel-breaking fluid is decreased by almost half. The adsorption capacity (<1.0 mg/g) gradually decreased with the increase of salinity at 20 °C. Moreover, the adsorption of gel-breaking fluids on the rock decreased first and then kept stable with temperature increasing at a salinity of ≤30,000 mg/L, however, showed the opposite trend at 40,000 mg/L. The results of rheology, particle size, static adsorption, and core damage showed that this functional FF could be an alternative for the stimulation of a tight reservoir with high temperature and recycling of produced water with high salinity.

Adsorption resin/polyethersulfone membrane used for plasma separation and middle molecular toxins adsorption

Accumulation of endogenous and exogenous toxins in patients with chronic kidney disease increases the kidney burden. The newly developed plasma separation adsorption membranes provide a new model for the removal of middle molecular toxins. In this study, the adsorption resin LX-1000H is physically pulverized and blended into polyethersulfone matrixes to prepare adsorption resin/polyethersulfone (AR/PES) membranes by nonsolvent-induced phase separation for plasma separation and middle molecular toxins absorption. The results show that the static adsorption capacity of AR/PES membrane for lysozyme (a typical mimic of middle molecular toxins) is up to 108.90 mg/g, which is 4 times that of AR. The maximum dynamic adsorption capacity reaches 102.80 mg/g, which is 93.4% of static adsorption. The adsorption process is more consistent with the Langmuir model and the quasi-first-order kinetic model. The permeability of bovine serum albumin in simulated blood surpasses 90% and the cattle blood separated by AR/PES membrane is colorless and transparent. The AR/PES membrane surface presents electronegative at pH 7.4 and the water wettability is enhanced with the doping amount. No hemolysis and negligible leakage indicated favorable hemocompatibility. This paper is devoted to providing a strategy for plasma separation and adsorption membranes.

Adsorbent Material Based on Carbon Black and Bismuth with Tunable Properties for Gold Recovery.

Adsorption recovery of precious metals on a variety of solid substrates has steadily gained increased attention in recent years. Special attention was paid to the studies on the characterization of the adsorptive properties of materials with a high affinity for gold depending on the nature of the pendant groups present in the structure of the material. The aim of the present work was to synthesize and characterize a new material by using the sol-gel synthesis method (designated as BCb/CB). In this case, synthesis involved the following precursors: bismuth carbonate (III), carbon black, and IGEPAL surfactant (octylphenoxypolyethoxyethanol). Immobilization of the heterojunction as bismuth oxide over a flexible support such as carbon black (CB) can prevent their elution in solution and make it versatile for its use in a system. In this work, a new adsorbent material based on bismuth carbonate supported over carbon black (BCb/CB) was developed and used further for gold recovery from aqueous solutions. The required material was characterized physically/chemically by scanning electron microscopy (SEM); energy dispersive X-ray spectrometry (EDX); X-ray diffraction (XRD); thermal analysis (DTG/DTA); atomic force microscopy (AFM). The Brunauer-Emmett-Teller (BET) method was used to determine the specific surface area indicating a value of approximately 40 m2/g, higher than the surface of CB precursor (36 m2/g). The adsorptive properties and the adsorption mechanism of the materials were highlighted in order to recover Au(III). For this, static adsorption studies were carried out. The parameters that influence the adsorption process were studied, namely: the pH, the contact time, the temperature, and the initial concentration of the gold ions in the used solution. In order to establish the mechanism of the adsorption process, kinetic, thermodynamic, and equilibrium studies were carried out. Experimental data proved that the gold recovery can be conducted with maximum performance at pH 3, at room temperature. Thermodynamic studies proved that the gold adsorption on BCb/CB material is a spontaneous and endothermal process. The results indicate a total adsorption capacity of 13.1 mg Au(III)/g material. By using this material in real solutions, a recovery efficiency of 90.5% was obtained, concomitant with a higher selectivity (around 95%).

Effectiveness and mechanisms of the adsorption of phenol from wastewater onto N-doped graphene oxide aerogel

Phenol, as a representative toxic substance in coking wastewater, will cause harm to the ecology and human beings. Therefore, advanced treatment of phenol is urgently needed. However, most adsorbents have the problems of low adsorption capacity and difficult recovery in water dephenolization. It is imminent to develop a recyclable and effective adsorbent. Herein three-dimensional (3D) N-doped graphene oxide aerogel (NGOA) was synthesized by using ammonium citrate as reductant and nitrogen source. NGOA exhibits large specific surface area, developed pores, excellent hydrophilicity and mechanical properties. The static and dynamic adsorption properties of NGOA were investigated. NGOA has good adsorption performance and reusability. The static saturated adsorption capacity of NGOA for phenol reached 108.19 mg g−1, which was obviously higher than most adsorbents. Furthermore, the dynamic adsorption capacity of NGOA was 43.69 mg g−1, which illustrates that NGOA has immense potential in the uptake of phenol for industrial application. Importantly, monolithic NGOA could be easily separated and recovered after adsorption saturation. The adsorption behavior conforms to the endothermic physical adsorption process, which is matched with the Pseudo-first-order kinetic model and Langmuir-Freundlich isotherm model. This work has good scientific research value and practical application prospect.

Selective degradation of ceftriaxone sodium by surface molecularly imprinted BiOCl/Bi3NbO7 heterojunction photocatalyst

By using the surface molecular imprinting technique, BiOCl/Bi3NbO7 was used as the substrate photocatalyst and ceftriaxone sodium (CTRX) was used as the template. A molecularly imprinted photocatalyst with specific recognition and photocatalytic synergy for CTRX was synthesized. Due to the excellent photoelectric properties and the successful formation of CTRX-imprinted cavities on the imprinted layer surface. The characterization results showed that MIP-3 has the advantages of uniform particle size and high separation efficiency of photogenerated carriers. The molecularly imprinted photocatalyst MIP-3 showed remarkable synergy and selectivity in both adsorption-photocatalysis of CTRX. Further experimental results showed that MIP-3 exhibited high selective adsorption performance for both high and low concentrations of CTRX in the 30 min static adsorption experiment. About 92 % of CTRX was degraded in the 100 min light experiment, which was a large improvement compared with BiOCl/Bi3NbO7. The selectivity of MIP-BNO was evaluated by comparing the degradation efficiency of MIP-3 on CTRX and chloramphenicol (CIP). Compared to non-imprinted photocatalyst NIP-BNO, MIP-3 has a higher selectivity coefficient of 2.58 and a faster degradation kinetic rate of 0.0169 min−1. The stability experiments showed that MIP-3 has good recoverability and stability during photocatalytic degradation. The mechanism of selective photocatalytic degradation of CTRX by MIP-3 was investigated by UV–visible spectroscopy, radical capture experiments, and electron spin tests. The possible degradation pathway of CTRX was also analyzed by LC-MS. In conclusion, this study confirms that the combination of surface molecular imprinting and photocatalyst has great potential to provide a promising solution for the treatment of low-level, highly toxic target pollutants in mixed wastewater.

Green and cost-efficient functionalized clay adsorbent enables one-step ultraefficient removal of Pb(II) at very low and high concentrations

It is always a huge challenge to purify wastewater containing very low or high concentrations of heavy metal ions to drinking water level (World Health Organization (WHO) guidelines) by one-step static or dynamic adsorption with a highly efficient, cost-effective, and environmentally friendly adsorbent. In response to this challenge, a green, low cost and powerful porous silicate/Fe3O4 adsorbent (named MCSiMg49) with ultra-strong purification ability towards the Pb(II) in both low- and high-concentration wastewater was developed using natural abundant, safe, and nontoxic palygorskite-rich clay as the starting material and water as the only solvent. The adsorbent possesses a high specific surface area of 332.41 m2/g (2.81 times that of raw clay), and was proven to be the best one to date that can purify deeply Pb(II) in water. The adsorption capacity of the adsorbent towards Pb(II) reached 499.3 mg/g, and 99.8% of Pb(II) can be removed from 800 mg/L Pb(II) solution after adsorption with 3 g/L of the adsorbent, which is significantly superior to other adsorbents and commercial activated carbon (AC). The adsorption column packed with MCSiMg49 (1 g, upper layer) and clay (1 g, lower layer) can remove completely Pb(II) from natural water (e.g., Yangtze River water or Yellow River water) (concentration: 50 mg/L), and 3000 mL clean drinking water (WHO guidelines) was obtained by a one-step filtration process. The MCSiMg49 adsorbent is easy to use in both dynamic and static adsorption, because it can be quickly recycled from the solution by external magnetic field after use. The adsorption of Pb(II) on the adsorbent was mainly driven by the cooperation of electrostatic attraction, ion exchange, chemical complexation and in situ mineralization of Pb(II).

Influence of Henna Extracts on Static and Dynamic Adsorption of Sodium Dodecyl Sulfate and Residual Oil Recovery from Quartz Sand.

The application of surfactant flooding for enhanced oil recovery (EOR) promotes hydrocarbon recovery through reduction of oil-water interfacial tension and alteration of oil-wet rock wettability into the water-wet state. Unfortunately, surfactant depletion in porous media, due to surfactant molecule adsorption and retention, adversely affects oil recovery, thus increasing the cost of the surfactant flooding process. Chemical-based materials are normally used as inhibitors or sacrificial agents to minimize surfactant adsorption, but they are quite expensive and not environmentally friendly. Plant-based materials (henna extracts) are far more sustainable because they are obtained from natural sources. However, there is limited research on the application of henna extracts as inhibitors to reduce dynamic adsorption of the surfactant in porous media and improve oil recovery from such media. Thus, henna extracts were introduced as an eco-friendly and low-cost sacrificial agent for minimizing the static and dynamic adsorption of sodium dodecyl sulfate (SDS) onto quartz sand in this study. Results showed that the extent of surfactant adsorption was inversely proportional to the henna extract concentration, and the adsorption of the henna extract onto the quartz surface was a multilayer adsorption that followed the Freundlich isotherm model. Precisely, the henna extract adsorption on quartz sand is in the range of 3.12-4.48 mg/g (for static adsorption) and 5.49-6.73 mg/g (for dynamic adsorption), whereas the SDS adsorption on quartz sand was obtained as 2.11 and 4.79 mg/g at static and dynamic conditions, respectively. In the presence of 8000 mg/L henna extract, SDS static and dynamic adsorption was significantly reduced by 64 and 82%, respectively. At the same conditions, the residual oil recovery increased by 9.2% over normal surfactant flooding. The study suggests that the use of henna extracts as a sacrificial agent during SDS flooding could result in the reduction of static and dynamic adsorption of surfactant molecules on quartz sand, thus promoting hydrocarbon recovery from sandstone formations.

Adsorption reduction of a gemini surfactant on carbonate rocks using formic acid: Static and dynamic conditions

Surfactant flooding improves oil recovery by lowering the interfacial tension and/or altering the reservoir rock’s wettability. However, surfactant losses caused by adsorption on the surface of the rock weaken the efficiency of this chemical enhanced oil recovery process. This study focuses on reducing the adsorption of a cationic gemini surfactant on carbonate rocks using formic acid. High-performance liquid chromatography integrated with an evaporative light scattering detector was employed to quantify both static and dynamic surfactant adsorptions. The results showed that the surfactant’s adsorption on carbonate rocks was reduced dramatically by adding 1% formic acid to the surfactant solution. Static adsorption was reduced from 2.44, 1.62, and 1.51 mg/g-rock to 0.16, 0.14, and 0.13 mg/g-rock on Guelph dolomite, Guff dolomite, and Indiana limestone, respectively. The dynamic adsorption of the surfactant on Indiana limestone was reduced from 0.269 to 0.041 mg/g-rock. It is believed that the carboxyl group released by the formic acid-rock reaction shields the surfactant from the rock surface resulting in lower adsorption. This is evidenced by the surfactant solution’s pH dropping below the point of zero charge of the rock, causing the repulsion of the cationic surfactant molecules off the surface. This study provides a low-cost option that provides a remarkable reduction in cationic surfactant adsorption on carbonate rocks.

Preparation of biochar@chitosan-polyethyleneimine for the efficient removal of uranium from water environment

A novel chitosan-based composite with rich active sites was synthesized by uniformly dispersing biochar into the cross-linked network structure formed by chitosan and polyethyleneimine. Due to the synergistic effect of biochar (minerals) and chitosan-polyethyleneimine interpenetrating network (amino and hydroxyl), the chitosan-based composite possessed an excellent adsorption performance for uranium(VI). It could rapidly (<60 min) achieve a high adsorption efficiency (96.7 %) for uranium(VI) from water and a high static saturated adsorption capacity (633.4 mg/g), which was far superior to other chitosan-based adsorbents. Moreover, the separation for uranium(VI) on the chitosan-based composite was suitable for a variety of actual water environments and the adsorption efficiencies all exceeded 70 % in different water bodies. The soluble uranium(VI) could be completely removed by the chitosan-based composite in the continuous adsorption process, which could meet the permissible limits of the World Health Organization. In sum, the novel chitosan-based composite could overcome the bottleneck of current chitosan-based adsorption materials and become a potential adsorbent for the remediation of actual uranium(VI) contaminated wastewater.