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The following supporting information can be downloaded at: https:// www.mdpi.com/article/10.3390/pr11041009/s1, Sulfamethoxazole [SMX] and metronidazole [MNZ] are emergent pollutants commonly found in surface water and wastewater, which can cause public health and environmental issues even at trace levels. An efficient alternative for their removal is the application of adsorption technology. The present work evaluated single and binary adsorption processes using granular activated carbon (CAG F400) for SMX and MNZ in an aqueous solution. The binary adsorption process was studied using a Box-Behnken experimental design (RSD), and the results were statistically tested using an analysis of variance. Density functional theory (DFT) modeling was employed to characterize the interactions between the antibiotics and the CAG F400 surface. For the individual adsorption process, adsorption capacities (q(e)) of 1.61 mmol g(-1) for SMX and 1.10 mmol g(-1) for MNZ were obtained. The adsorption isotherm model that best fit experimental data was the Radke-Prausnitz isotherm model. The adsorption mechanism occurs through electrostatic and pi-pi dispersive interactions. For the binary adsorption process, the total binary adsorption capacity achieved was 1.13 mmol g(-1), evidencing competitive adsorption. The significant factors that determine the removal of SMX and MNZ from a binary solution were the solution pH and the initial concentration of antibiotics. From DFT studies, it was found that SMX adsorption on CAG F400 was favored with adsorption energy (E-ads) of -10.36 kcal mol(-1). Finally, the binary adsorption results corroborated that the adsorption process was favorable for both molecules., Consejo Nacional de Ciencia y Tecnologia (CONACyT)

In this study, a series of molecularly imprinted polymers (MIPs) have been synthesized using separately diclofenac, naproxen, and ibuprofen as templates with three different polymerization approaches. Two functional monomers, methacrylic acid (MAA) and 2-vinylpyridine (2-VP), were tested and ethylene glycol dimethacrylate (EGDMA) was used as crosslinker; also, template-free polymers (NIPs) were synthesized. It was found that the MIP with the highest retention percentage for diclofenac was the one prepared by the emulsion approach and with MAA (98.3%); for naproxen, the one prepared by the bulk polymerization with MAA (99%); and for ibuprofen, the one synthesized by bulk with 2-VP (97.7%). These three MIPs were characterized by scanning electron microscopy, thermogravimetric test, Fourier transform infrared, specific area measurements, and surface charge. It was found that the emulsion method allowed particle size control, while the bulk method gave heterogeneous particles. The three evaluated MIPs exhibited thermal stability up to 300 °C, and it was observed that 2-VP confers greater stability to the material. From the BET analysis, it was demonstrated that the MIPs and NIPs evaluated are mesoporous materials with a pore size between 10 and 20 nm. In addition, the monomer influenced the surface charge of the material, since the MAA conferred an acidic point of zero charge (PZC), while the 2-VP conferred a PZC of basic character. Through adsorption isotherms, it was determined that there is a higher adsorption capacity of the MIPs at acidic pH following a pseudo-second-order kinetic model. Finally, the MIPs were used to determine the non-steroidal anti-inflammatory drugs (NSAIDs) understudy in San Luis Potosí, México, wastewater, finding concentrations of 0.642, 0.985, and 0.403 mg L

The chemical enhanced oil recovery (cEOR) uses substances to improve the mobility of petroleum in reservoirs. Among these substances are the surfactants, whose purpose is to change the wettability and interfacial tension (IFT). We focus on experiments of surfactants in rocks from Chicontepec Paleochannel. CTAB, DTAB and SDS surfactants in brines of NaCl and KCl and mineral oil were investigated for reduction of IFT and contact angle alteration. The sessile and pendant drop methods were used to determine the IFT. The electrical affinity of the rock surface, dissolved ions, and the surfactant molecules, play key roles in the alteration of wettability and IFT. Thus, one scheme of interactions between the electrical charges is proposed on the basis of the rocky characterization and the following results: the lowest contact angle was 106° with CTAB at 0.01 wt% in brines at 9.25 g/L NaCl, and 108° with SDS at 0.01 wt% in brines at 20 g/L NaCl. The smallest IFT was 0.813 dyn/cm with CTAB at 0.5 wt% in brines at 5 g/L KCl. This work serves as first assessments of these surfactants to enhance the production in Chicontepec, employing cheap tensoactives to increase the applicability. Besides, these results will guide future displacement tests as cEOR lab simulation.

In this work, the potential of activated carbon to remove caffeic and chlorogenic acids was investigated. The study focused on evaluating the single and binary adsorption equilibrium, as well as investigating the mass transfer resistances present during the process by applying kinetic and diffusional models for a future scale-up of the process. For both compounds, the single adsorption equilibrium was studied at pH values of 3, 5, and 7. The experimental adsorption isotherms were interpreted using the Langmuir and Freundlich models, obtaining maximum adsorption capacities of 1.33 and 1.62 mmol/g for caffeic and chlorogenic acid, respectively. It was found that the adsorption mechanisms for both compounds was derived from π-π and electrostatic interactions. Also, the binary adsorption equilibrium was performed and the experimental data were interpreted using the extended multicomponent Langmuir model. The results evidenced that the binary adsorption of caffeic acid and chlorogenic acid is antagonistic in nature. The application of the first and second order kinetic models showed that the latter interpreted better the experimental data, obtaining R2 values close to one. Finally, the experimental adsorption rate data were interpreted by a diffusional model, finding the presence of different mass transfer resistances during the adsorption process. For both compounds, intraparticle diffusion mechanisms were meaningful.

The removal of contaminants from water solution by biosorption on biowaste materials, such as natural wood sawdust (NWS), has been extensively studied recently. The interpretation of the experimental biosorption rate data is an important issue and has to be performed using mathematical models based upon phenomenological principles. An experimental stirred tank batch adsorber was employed to obtain the biosorption rate data of methylene blue (MB) on NWS, which were interpreted using kinetic and diffusional models. The pseudo-second order (PSO) kinetic model adequately represented the experimental data, but its kinetic constant changed significantly with the operating conditions, hampering its practical application. A new diffusion-permeation model (DPM) is proposed by assuming that the intraparticular transport of pollutants is due to the simultaneous diffusion in the voids and permeation through the biosorbent walls. The DPM model fitted the experimental data satisfactorily, and the diffusion-permeation coefficient, DPM, varied slightly with the experimental conditions. The DPM model matched the experimental data adequately using an arithmetic mean of the DPM coefficient, D P M ¯ . Finally, the predictions of the DPM model using D P M ¯ were compared to those estimated with the PSO model. In most of the experimental cases, the experimental data was better predicted by the DPM model.

In the current work, a deep study to understand the adsorption phenomena occurring in single and multicomponent systems was conducted by using spectroscopic characterization, and computational tools. The experimental results showed that the adsorption capacity of chili seed is higher for Pb2+ (48 mg/g) than Cu2+ (4.1 mg/g) ions in single systems. However, the adsorption study in multicomponent systems provides important conclusions of the concentration effect of the metal ions, showing a significant antagonistic and competitive effect of both ions under equivalent concentrations of them (qPb2+ is 56% reduced) or high concentration of Pb2+ (qCu2+ is 50% reduced). Computational results correlated well with the experimental ones and evidenced all interactions proposed from spectroscopy results, accounting for the occurrence of complexation and electrostatic mechanisms between metal ions and the surface oxygenated functional groups (hydroxyl, carboxyl, and carboxylate) onto chili seed. Chemistry quantum descriptors supported the reactivity behavior of the chemical species implicated. All results evidenced that Pb2+ and Cu2+ adsorption on chili seed surface is governed by the occurrence of combined ionic exchange, π-interaction, complexation, and electrostatic attraction.

In this work, a mathematical formulation based on fundamental principles of momentum and mass transport with a kinetic adsorption model at the liquid-solid interface is proposed. This formulation was numerically solved and used for the interpretation of adsorption rate data of phenol onto an activated carbon cloth in a stirred tank adsorber under different agitation rates. The mathematical model solution was compared with the obtained by mathematical models that neglect the local velocity and concentration profiles in the solution; external mass transfer model (EMTM) and the first-order kinetic model (FOM). The results showed that under all studied stirring speeds (30−200 rpm) the proposed model was able to capture the dynamics of the concentration decay curves, while EMTM and FOM models were only able to interpret the data at high stirring speeds, indicating that velocity profiles play an important role during phenol adsorption. Particular “wake zones” were identified behind the mobile adsorbent, which importantly promotes the transport of solute toward the activated carbon cloth. As a result, it was found that convective transport is much more important than diffusive transport in the solution.

The experimental and numerical analysis of pyridine adsorption onto activated carbon cloth in a stirred batch adsorber under transition and turbulent regime is presented in this work. Three-dimensional numerical modeling of the adsorption process was implemented for the identification of local velocity, local concentration, and concentration gradients inside the adsorber. This represents a costly computational effort in comparison with conventional batch adsorption models, as for instance the Langmuir kinetic model. Both types of modeling yield comparable results, but the advantage of the 3D modeling is a more detailed resolution of variables, thus avoiding the perfectly mixed assumption. Varying the agitation rate (30–200 rpm) and pyridine initial concentration (99 to 487 mg/L), several kinetic and transport parameters were reported. Hydrodynamic and mass boundary layers are identified around the activated carbon adsorbent following the trajectory of agitation. Furthermore, the major pyridine mass flux takes place around the adsorbent, mainly in the posterior zone regarding the agitation direction. This information is crucial in searching for and designing more efficient and intensive adsorbent systems.

This work studied the application of adsorption with activated carbons (ACs) and photodegradation to reduce the concentration of triclosan (TCS) in aqueous solutions. Concerning the adsorption, the ACs (Darco, Norit, and F400) were characterized in detail, and batch experiments were applied to elucidate the effect of pH on the equilibrium. The results showed that at pH = 7, the maximum adsorption capacity of TCS onto the ACs was obtained, which was 18.5 mg g− 1 for Darco, 16.0 for Norit, and 15.5 for F400. The Diffusional kinetic model allowed an adequate interpretation of the experimental data. The effective diffusivity varied and increased along with the amount of TCS adsorbed, from 1.06 to 1.68×10− 8 cm2 s− 1. In the case of photodegradation, the removal percentage of TCS and sulfate radicals were verified. It was possible to ensure that the triclosan molecule was sensitive to UV light of 254 nm since the removal was over 80% using UV light. The removal of TCS was increased in the presence of sulfate radicals. It was possible to identify 2,4-dichlorophenol as one of the photolytic degradation products of triclosan, and it does not represent an environmental hazard at low concentrations of triclosan in water. These results confirm that the wastewater treatment methods proposed are effective for removing TCS from water, reaching levels of concentration that do not constitute a risk to human health or environmental hazard. Both methods effectively eliminate the pollutant with relatively easy techniques to implement.

In this work, the degradation of sulfamethazine (SMT), sulfadiazine (SMD), and sulfamethoxazole (SMX) by using UV light, UV/H2O2, and UV/S2O8-2 was analyzed. Direct photolysis was studied by varying the lamp power and the solution pH. DFT calculations were carried out to corroborate the efficiency of the degradation as a function of the solution pH. The variation of the apparent rate constant, kap, was determined in the indirect photolysis by employing an experimental Box-Behnken-type response surface design. The results evidenced that SMX can be efficiently degraded by applying UV radiation independent of the operating conditions. Nevertheless, the quantum yields for SMT and SMD were close to zero, indicating a low energy efficiency for their photochemical transformation. The effect of the solution pH showed that the photodegradation of sulfonamides depends both on the amount of radiation absorbed as the electronic density. Calculations based on density functional theory and supported by the quantum theory of atoms in molecules allowed to describe fragmentation patterns in the systems under study, proving the lability of S14-C2, N17-C18, and N22-O22 bonds, for SMT, SMD, and SMX, respectively. From response surface methodology, four statistically reliable equations were obtained to determine the kap value as a function of the system operating conditions. Finally, SO4•- radicals proved to have a higher reactivity to degrade SMT and SMD compared with HO• radicals regardless of the operating conditions of the system.

In this study, bone chars were obtained from an alien aquatic species “devilfish” bones by pyrolysis of 500–800 °C. Bone chars were evaluated as a sustainable adsorbent of fluoride, and it was found pyrolyzed bone char at 500 °C adsorbed the most amount of fluoride. Thermodynamic parameters of fluoride adsorption on devilfish bone chars were estimated as ΔH° = 7.213 kJ mol−1, ΔG° = 23.61 kJ mol−1, and ΔS° = 103.4 J mol−1 K−1 indicating that adsorption is endothermic, spontaneous, and with a great affinity of fluoride on bone char. The fluoride desorption study showed that fluoride is desorbed from the material of 0.24 to 20.06%, so the adsorption is considered to be partly reversible. The regeneration of the bone char at 400, 500, and 600 °C was studied, and it was noted that its adsorption capacity decreases slightly, so it could be considered appropriate for the use in water treatment technologies. Adsorption of fluorides from drinking well water of a rural community with dental fluorosis problems and high levels of fluoride in water revealed that by increasing the amount of the bone char of 0.05 to 0.8 g, the disposal of fluoride increases from 69.1 to 98.7%. Lastly, it was established that the bone char synthesized from devilfish is a low-cost, viable, sustainable material to remove fluorides from water and represents an environmental management strategy of this alien species.

Nanostructured porous silicon microparticles (μPSip) synthesized by electrochemical etching were used as tunable carriers for sustained delivery of metformin hydrochloride (MET), an oral antihyperglycemic agent. The surface of native PSi microparticles was modified by thermal oxidation to enhance μPSip stability and MET physical adsorption. Morphological and physicochemical properties of the porous carrier were characterized by a combination of scanning electron microscopy, nitrogen adsorption–desorption, and zeta potential techniques. Drug loading was confirmed by ATR Fourier transform infrared spectroscopy, and loading efficiency was quantified by thermogravimetric analysis and UV–Vis. From MET released profiles, we demonstrated that thermally oxidized µPSip exhibited a sustained release during 26 h, with burst effect depending on pH of the microenvironment. Native PSi loaded particles showed a complete MET release within 6 h with a substantial burst effect at 1 h. The loading kinetics of MET at different initial concentrations were satisfactorily predicted with a 3D diffusional model based on surface diffusion. The proposed model showed that the surface diffusion coefficient (Ds) values increase exponentially as a function of MET loading. The mass transport parameters obtained from the loading kinetics were used to predict the release kinetics of MET. The comparison of experimental and predicted results showed an accurate representation of the data, highlighting the reliability of the model. Through in vivo studies, it was demonstrated that MET-μPSip microcarriers did not induce inflammatory processes. A sustained hypoglycemic effect was observed for 24 h after composite administration, which is a novel contribution of this work.

The adsorption rate of sodium dodecylbenzenesulfonate (SDBS) on three commercial activated carbons (ACs) and an AC synthesized from almond shells was investigated in this study. The mechani...

An innovative and environmentally-friendly procedure has been developed for the successful preparation of Ta2O5 nanoparticles (NPs). This method includes mechanical milling and a subsequent calcination step. The in-situ formation of LiCl/KCl and the partial crystallization of Ta2O5 at low-temperature were observed after milling, confirming the existence of chemical reaction between TaCl5 and LiOH/KOH reagents, and also the mechanochemical synthesis of Ta2O5. By heating at 700 °C during 2 h, complete crystallization of Ta2O5 was achieved. The synthesized Ta2O5 NPs showed flake shape with sizes below 20 nm and SBET of 17 m2 g−1. Furthermore, the proposed method represents an alternative for the straightforward and large-scale production of crystalline Ta2O5 NPs. Moreover, the as-prepared Ta2O5 NPs showed high photocatalytic activity for degrading methylene blue (MB) dye. The Ta2O5 NPs enhanced the degradation rate of MB attaining a degradation percentage of about ⁓ 81% within 180 min under UV–vis irradiation. Herein, trapping experiments demonstrated that holes are the main oxidative species in the MB photodegradation process. After recycling tests, the Ta2O5 NPs showed high stability which demonstrates that this photocatalyst is suitable for use in wastewater treatment.

In this work chili seeds (Capsicum annuum) were used as raw material in the synthesis of biochar at temperatures between 400 and 600 °C. The samples were chemically, texturally and morphologically characterized and their properties were correlated with the calcination temperature. The adsorption mechanism of IBP was elucidated by analyzing the effect of solution pH, ionic strength and temperature, whereas that, the intraparticle diffusion mechanism was clarified through the application of a 3D diffusional model. The results evidenced that raising the pyrolysis temperature promotes a greater content of disordered graphitic carbon (51.6–85.02%) with small surface area (0.52–0.18 m2/g) and low quantity of functional groups. The adsorption study demonstrated that the biochar synthesized at 600 °C (C600) enhances the adsorption capacity >50 folds compared with chili seeds. Moreover, at pH = 7 the adsorption mechanism is governed by π-acceptor and attractive electrostatic interactions, whereas at basic pH the main adsorption mechanism is π-acceptor. Additionally, hydrophobic interactions become important by increasing the presence of NaCl. The application of 3D diffusional model based on surface diffusion interpreted clearly the kinetic curves obtaining values of Ds ranging from 2.31 × 10−8–2.51 × 10−8 cm2 s−1. Besides, it was determined that intraparticle mass flux is larger along the shortest axis of the seed, and always directed toward the particle center. The maximum mass flux takes place in the center of particle, and it advances like a moving front as time was increased.

The aim of this work was to determine whether the effectiveness of hydroxyl and sulfate radicals to degrade carbamazepine (CBZ) in aqueous solution is a function of the radical generator system used. For this purpose, an in-depth analysis was conducted of CBZ degradation by UV radiation, UV/H2O2, UV/S2O82−, Fe2+/H2O2, Fe2+/S2O82−, UV/Fe2+/H2O2 and UV/Fe2+/S2O82−. Results obtained show that CBZ can be degraded by direct photolysis but that the effectiveness is very low, with a quantum yield near zero. CBZ can be effectively degraded by UV/H2O2 and UV/S2O82- systems, with percentages close to 100%. CBZ degradation was 1.26- to 2.0-fold faster with SO4 - radicals than with HO radicals. In contrast, CBZ degradation was 1.1- to 1.7-fold more effective with the Fe2+/H2O2 versus Fe2+/S2O82- system when the Fenton process was applied. CBZ removal from water was most effective with UV/Fe2+/H2O2 and UV/Fe2+/S2O82− systems, attributable to the additional generation of HO radicals resulting from the reduction in Fe3+. A slight decrease in percentage degradation was observed with all systems when wastewater was the aqueous matrix, mainly due to the presence of organic and inorganic species that may act as radical scavengers (Cl-, NO2-, NO3- and SO42−). Finally, the highest percentage mineralization was obtained with the UV/Fe2+/H2O2 system in deionized water.

In the present work, the preparation of activated carbon pellets from cigarette butts by thermal treatment was evaluated. The morphological, textural, topological, and surface chemical properties were studied by SEM-EDX, N2 adsorption, Raman, and FTIR spectroscopy. For adsorption assays, activated carbon was tested for the adsorption of phenol as a model molecule at different solution pH, temperature, and type of water. In addition, leaching tests before and after carbonization were conducted to evaluate the lixiviation of ions present in the solid. The results revealed a microporous material, composed of cylindrical fibers (thickness of 13 µm) with a microporous area of 713 m2/g and narrow and uniform slit-shaped pores (0.4–0.8 nm). The surface chemistry analysis evidenced the presence of oxygenated groups (carboxylic, esters, and phenolics). Activated carbon leaching tests indicated that the concentrations of the leached ions did not exceed the maximum permissible limit for drinking water. Phenol adsorption revealed an exothermic process with a maximum adsorption capacity of 272 mg/g at 10 °C. Finally, it was confirmed that phenol diffusion was drastically affected by hindered phenomena due to the similarity in the molecular size of phenol and the average size of micropores, and as a result an effective diffusion coefficient between 6.10 × 10−0 and 5.50 × 10−12 cm2/s and a maximum tortuosity value of 3.3 were obtained.

This study focuses on evaluating the volumetric hydrogen content in the gaseous mixture released from the steam catalytic gasification of n-C7 asphaltenes and resins II at low temperatures (

In this study, bone chars were obtained from an alien acuatic species “devilfish” bones by pyrolysis of 500–800°C. Bone chars were evaluated as a sustainable adsorbent of fluoride, it was found pyrolysed bone char at 500°C adsorbed the most amount of fluoride. The effect of pH indicated that the adsorption capacity increased as the pH decreased. Thermodynamic parameters of fluoride adsorption on devilfish bone chars were estimated as ΔH°= 7.213 kJ mol− 1, ΔG°= 23.61 kJ mol− 1 and ΔS° = 103.4 J mol− 1 K− 1 indicating that adsorption is endothermic, spontaneous and with great affinity of fluoride on bone char from devilfish. The fluoride desorption study showed that fluoride is desorbed from the material of 0.24 to 20.06 %, so the adsorption is considered to be partly reversible. The regeneration of the bone char at 400, 500 and 600°C was studied and it was noted that its adsorption capacity decreases slightly so it could be considered appropriate for the use in water treatment technologies. Adsorption of fluorides from drinking well water of a rural community with dental fluorosis problems and high levels of fluoride in water, revealed that by increasing the amount of the bone char of 0.05 to 0.8 g, the disposal of fluoride increases from 69.1 to 98.7 %. Lastly, it was established that the bone char synthesized from devilfish is a low-cost, viable a sustainable material to remove fluorides from water and represents an environmental management strategy of this alien species.

Three-dimensional (3D)-printed catalysts are being increasingly studied; however, most of these studies focus on the obtention of catalytically active monoliths, and thus traditional channeled monolithic catalysts are usually obtained and tested, losing sight of the advantages that 3D-printing could entail. This work goes one step further, and an advanced monolith with specifically designed geometry has been obtained, taking advantage of the versatility provided by 3D-printing. As a proof of concept, nonchanneled advanced monolithic (NCM) support, composed of several transversal discs containing deposits for active phase deposition and slits through which the gas circulates, was obtained and tested in the CO-PrOx reaction. The results evidenced that the NCM support showed superior catalytic performance compared to conventional channeled monoliths (CMs). The region of temperature in which the active phase can work under chemical control, and thus in a more efficient way, is increased by 31% in NCM compared to the powdered or the CM sample. Turbulence occurs inside the fluid path through the NCM, which enhances the mass transfer of reagents and products toward and from the active sites to the fluid bulk favoring the chemical reaction rate. The nonchanneled monolith also improved heat dispersion by the tortuous paths, reducing the local temperature at the active site. Thus, the way in which reactants and products are transported inside the monoliths plays a crucial role, and this is affected by the inner geometry of the monoliths. The authors are grateful for the financial support of the Spanish Ministry of Economy and Competitiveness (Project CTQ2015-67597-C2-2-R), The University of Alicante (Project GRE18-01A), Generalitat Valenciana (Project PROMETEO/2018/076, Ph.D. grant GRISOLIAP/2017/177, and contract APOSTD/2019/030), Junta de Andalucía (Project P18-RTJ-2974), and the UE (FEDER funding).

Due to the sulfur dioxide (SO2) negative effects to the environment and human health, its removal is currently of great importance to policy markers and researchers. In this context, the present work had the aim to study the SO2 dynamic adsorption behavior on two activated carbons rich on calcium species. One material prepared directly from peach stone shell (PC) and the other prepared from raw material treated with CaCl2 (PCCa) with the purpose to increase the interaction of sulfur with calcium compounds on the surface and to augment its surface area. The obtained activated carbons were characterized using N2 adsorption at 77 K, IR, XRD and SEM/EDX analysis. PCCa carbon presented the higher adsorption capacity compared with PC material, indicating that the surface area and the increase of calcium groups (Ca(OH)2, CaCO3, CaO) are playing an important role during the adsorption of SO2. Additionally, the results demonstrated that as temperature increases the adsorption capacity decreases. On the other hand, the dynamic studies revealed that the residence time reached at 150 mL min-1 flow-rate was the most efficient for the mass transfer processes. Also, the results demonstrated that the presence of moisture decreases the adsorption capacity due to the presence of water molecules on the adsorbent surface. The dynamic adsorption results were modeled using: the Advection-dispersion model, FANN and the conventional models Thomas and Yan. The results shown that the FANN model was the best to correlate the adsorption breakthrough curves of SO2., This work was supported by Secretaria de Educación Pública de México resources “Apoyo a la incorporación de NPTC” UCOL-PTC-255.

In this work, walnut shell (WS) (Carya illinoinensis) treated with citric acid was used as biosorbent to remove zinc ions from aqueous solution. The effect of citric acid concentration and solution pH on the adsorption equilibrium was investigated in batch experiments. Additionally, the overall adsorption rate of Zn ions on walnut shell treated with citric acid was investigated by applying a diffusion model based on superficial diffusion. The results evidenced that a maximum adsorption capacity towards Zn(II) ions is obtained by using a citric acid concentration 2 M (WS2). The modification of walnut shell increases 2.5 times its adsorption capacity to remove Zn(II) from aqueous solutions due to the incorporation of carboxylic groups reaching a maximum adsorption capacity of 27.86 mg/g. The pH effect showed that the adsorption capacity was drastically increased by raising the solution pH from 3 to 6. The adsorption kinetics of Zn(II) on WS2 were interpreted correctly by the surface diffusional model (SDM). The values of Ds varied from 2.25 to 5.25 × 10−9 cm2/s, and increased exponentially as the mass of Zn(II) adsorbed at equilibrium augmented.

In this work, the adsorption rate of metronidazole (MNZ) on activated carbon from aqueous solution at low and high concentrations was studied thoroughly by the application of a diffusional model in three dimensions. The diffusional model considers the external mass transport, intraparticle diffusion (pore volume diffusion and surface diffusion) and the adsorption on an active site. Additionally, the effect of the mass of MNZ adsorbed at the equilibrium (qe) on the magnitude and direction of surface diffusion and pore volume diffusion fluxes were analyzed in detail. The results revealed that the time to reach adsorption equilibrium drastically increases from 630 min to 19,000 min as the qe value diminished from 223.94 to 60.20 mg/g due to a decrease in the concentration gradient in the aqueous phase. The application of the diffusional model showed that surface diffusion is more relevant than pore volume diffusion, but its importance is a function of qe. At qe values less than 200 mg g−1, the intraparticle diffusion of MNZ is controlled by surface diffusion, whereas at values higher than 200 mg g−1, the contribution of pore volume diffusion is considerable at times close to equilibrium time. The values of Ds increased exponentially from 0.02 × 10−8 to 2.67 × 10−8 cm2/s as qe increased. Finally, the surface diffusion model can be applied to interpret the adsorption rate of MNZ at low concentrations of MNZ in water.

A three-dimensional mass transfer model (pore volume and surface diffusion model, PVSDM 3D) was applied to elucidate the ibuprofen adsorption on standard (SAC) and ultrasound modified (USAC) activated carbons. Experimental isotherms and kinetic curves were constructed at pH 2.0 and 298 K. The results revealed that USAC presented higher values of surface area, pore diameter, pore volume and void fraction than SAC, demonstrating that the ultrasonic modification was efficient to improve the characteristics of activated carbon. The adsorption capacities obtained using USAC carbon were around 25% higher in relation to the obtained using SAC carbon. For both adsorbents, the Redlich–Peterson model was able to predict the isotherm data. At pH of 2.0, dispersive interactions π–π and donor–acceptor interactions between the aromatic ring of ibuprofen and carbonyl groups of the activated carbons occurred. The concentration decay curves obtained with USAC required less time to reach equilibrium due to its modification of textural properties. The application of PVSDM 3D model evidenced that the DS (surface diffusion coefficient) values for USAC were around 1.7 folds greater than those obtained by SAC, besides it was corroborated that the magnitude of total intraparticular flux is a function of time and position inside the particle. It was verified that the ibuprofen molecule diffuses exclusively by surface diffusion and that the diffusion in the pore volume can be neglected. The DS values ranged from 1.8 × 10−9 to 33.6 × 10−9 cm2 s−1.

In this work, Simple Walled Carbon Nanotubes (SWCNTs) were used as adsorbents to remove triclosan (TCS) from aqueous solution. The material characterization consisted of SEM/EDS and TEM/EDS analysis, surface characterization, and the determination of the pH at the point of zero charge. The effect of solution pH on the adsorption equilibrium was investigated in batch experiments. The overall adsorption rate of TCS on SWCNTs was investigated by applying kinetic models and a diffusional model based on pore volume diffusion. The results showed that a maximum adsorption capacity of TCS onto SWCNTs is obtained at a pH value of 7, which is 30.3 mg g−1. The adsorption kinetics of TCS on SWCNTs was interpreted correctly by the First Order Kinetic Model and the Diffusional Model. The values of Dep varied from 1.06 to 1.20 × 10−8 cm2 s−1 and increased discretely as the mass of TCS adsorbed at equilibrium increased.

This study aims to evaluate the reuse capacity of carbon xerogels-Ce/Ni composite (XCeNi) during crude oil adsorption from O/W emulsions and subsequent regeneration through the oxidation process using air as an oxidant agent for six cycles. For the six cycles of evaluation, batch adsorption experiments were done at different temperatures and modeled using the solid-equilibrium model (SLE). In contrast, catalytic tests were performed under non-isothermal and isothermal heating. To estimate the change in the sample's surface composition, X-ray photoelectron spectroscopy (XPS) analysis was carried out during each regeneration cycle. According to batch adsorption experiments and SLE fitting, the XCeNi sample presents a high affinity for hydrocarbons and a similar maximum adsorption capacity during six regeneration cycles. Crude oil was also successfully decomposed under non-isothermal heating (100–800 °C), reducing the main decomposition peak from 250 to 150 °C for all the evaluated cycles. Under isothermal heating at 150, 200, and 250 °C, conversions of 100% were obtained for all cycles evaluated. At the first cycle the time required to decompose 100% of adsorbed crude oil at 60 min, whereas, after the 6 cycle, it is achieved at 120 min. The gaseous analysis of the products involved in the oxidation of the crude oil in each cycle was considered, finding an increase in the production of light hydrocarbons and reducing gas emissions such as CO2, NOX, and SOX during all reuses. The activation energy increases from 10.1 to 18.7 kJ mol−1 during the six cycles due to the reduction of the content of Ce3+. The Ce3+ concentration is reduced to 0 after each adsorption cycle. Apparently, the ability of the xerogel to decompose the adsorbed crude during all cycles may be associated with the increase in Ce3+ during the adsorption process, and then during the oxidation treatment is transformed to Ce(OH)22+. Also, the influence of Ni2+ on XCeNi is noted. Through the regeneration, the Ni2+/Ni3+ ratio varies, which shows the continuous redox processes that have taken place in this sample.

In this study, a novel environmentally friendly diatomite-cross-linked​ β -Cyclodextrin (DA@ β -CD) adsorbent was synthesized by a one-step synthesis method for the removal of bisphenol A (BPA). The synthesized DA@ β -CD exhibits higher removal capacities for BPA than DA, which is 1.4 to 2.5 times of DA. The factors of influencing DA@ β -CD removal capacities, such as the dosage of DA@ β -CD, the pH, and temperature were investigated. Adsorption isotherms and kinetics followed the Langmuir (R adj 2 = 0 . 9942 ) and fitted well with pseudo-second-order​ (R adj 2 = 0 . 9995 –0.9999) and Langmuir-type kinetic models (R adj 2 = 0 . 9825 –0.9984). The intraparticle diffusion and external mass transfer models (EMTM) indicated that the mass transfer of BPA was controlled by external mass transport. The mechanism of removal of BPA in the DA@ β -CD system may be coordinated by three adsorption type pathways. Furthermore, the DA@ β -CD is stable and easy to regenerate with the alkaline solution, and the removal is maintained at 91.15% after three cycles. These results demonstrated that the DA@ β -CD has the potential for practical applications as a green and environmentally friendly adsorbent.

In this work the overall adsorption rate of acetaminophen on activated carbon pellets (ACP) was analyzed in deep. The concentration decay curves were interpreted by a 3D diffusional model because the intraparticle diffusion of acetaminophen inside ACP in radial and axial directions are important in this form of activated carbon. The 3D diffusional model considers the external mass transfer, intraparticle diffusion (pore volume and surface diffusion) and the adsorption on an active site. The results demonstrated that the application of 3D diffusional model based on pore volume diffusion interprets clearly the kinetic curves, however values of effective diffusion coefficient (Dep) higher than molecular diffusivity are obtained indicating superdiffusion phenomenon. On the other hand, the application of a general diffusion model evidenced that during the whole time interval, the acetaminophen diffuses consecutively by surface diffusion followed by pore volume diffusion. In short times the surface flux is higher than the pore volume flux, but at higher intervals of time, the relevance of both fluxes reverts. Finally, from 3D simulation it is clear that at longer times, the solute mainly enters from the solution through the pellet borders, and acetaminophen desorption signs are even evident at the center of the pellet covers, due to the inverse concentration gradient established between the pellet and the solution.

In this work, the single and binary adsorption of Cd(II) and Pb(II) onto industrial chili seeds (CS) ( Capsicum annuum ) from aqueous solutions was investigated as a possible low-cost biosorbent for the removal of toxic heavy metals from aqueous solutions. The dependence of the adsorption capacity of CS on the solution pH and temperature, and the presence of competitive metal were also studied in detail. The adsorption equilibrium experiments of Cd(II) and Pb(II) on CS were conducted in a batch adsorber. The Freundlich and Langmuir isotherm models were fitted to the single adsorption equilibrium data and the latter provided a better fit. Moreover, it was found that the adsorption capacity of CS towards Cd(II) and Pb(II) ions was greatly increased by increasing the solution pH. The effect of the pH was attributed to the electrostatic interaction between the negatively charged CS surface and the Cd 2+ and Pb 2+ cations in the aqueous solution. The adsorption capacity was slightly increased by raising the temperature because the adsorption of Cd(II) or Pb(II) ions on CS was an endothermic process. The experimental binary adsorption data were satisfactorily interpreted using the modified Langmuir multicomponent isotherm and the competitive adsorption of Cd(II)-Pb(II) on CS revealed that the affinity of Pb(II) for CS was more than 5 times higher than that of Cd(II).

Xerogels based on resorcinol-formaldehyde (XRF) doped with different doses of Tris(2,2′-bipyridine) ruthenium(II) (RuBpy) were synthesized and characterized, and their photoactivity was determined in the presence of solar radiation. The addition of RuBpy did not modify the morphological and textural properties of the xerogels, which were all ultramicroporous, with a mean micropore surface of 240 m2 g−1; micropore volume of 0.10 cm3 g−1, and pore diameter of 0.64 nm. The addition of RuBpy reduced the band gap energy (Eg) values of the xerogels, which were 5.68 eV for XRF and 0.98 eV for XRF doped with 150 mg L−1 of RuBpy (X150RuB), due to the inclusion of RuBpy as charge center. The photocatalytic activity of the doped xerogels in pollutant degradation by solar radiation was analyzed in the photooxidation of chlortetracycline (CTC) as a model pollutant. The degradation percentages of CTC were 35.23% for XRF, 36.17% for X50RuB, 50.16% for X150RuB, and 31.33% for direct photolysis. The effect of radical scavengers (NO3− and tert-butanol) on the degradation and XPS analysis demonstrated that the hydrated electron (eaq−) generated by irradiation in the charge centers of the material migrates through the material and interacts with its functional groups, promoting the generation of OH radicals and the reduction and subsequent deactivation of the material.

In this work, it was analyzed the behavior of three commercial activated carbons with different textural and chemical properties to adsorb individually metronidazole and lead ions from aqueous solution. Afterwards, the activated carbons were modified with citric acid to remove both compounds simultaneously. Both sets of activated carbons were characterized chemically and texturally. XPS analysis was performed to corroborate the adsorption mechanism of lead on the surface of the carbons. Finally, the intraparticle diffusion of both adsorbates was elucidated by the application of diffusional model in three dimensions. The results evidenced that adsorption mechanism for MNZ and Pb(II) is independent, the adsorption for MNZ is governed by π–π dispersive interactions, whereas Pb(II) adsorption is mainly controlled by electrostatic interactions. The binary adsorption equilibrium shows that the adsorption of MNZ is independent from the concentration of Pb(II), whereas the adsorption of Pb(II) is affected by the presence of MNZ at low concentrations (0.1 mmol L−1), but it remains almost constant at concentrations of MNZ between 0.1 and 1.5 mmol L−1. Finally, the mass transport of MNZ was faster than Pb(II) from the solution to the external surface of activated carbon and the mass flux of MNZ inside the particle was superior to the mass flux of Pb(II). Lastly, there might be an obstruction phenomenon with MNZ impeding Pb(II) to reach the active sites placed into the carbon’s microporosity structure.

A series of activated carbons (ACs) were prepared by modifying a commercial AC by physical activation using CO2 during different activation times. The ACs were designated as F, F12, F24, and F40 corresponding to the activation times of 0, 12, 24, and 40 h, respectively. The surface area, total pore volume, micropore volume, and mean micropore width were determined for all the ACs. The textural properties of the modified ACs increased substantially with the activation time, and the capacity of the ACs for adsorbing diclofenac (DCF) was almost linearly dependent upon the surface area of the ACS. The maximum adsorption capacities of F, F12, F24, and F40 carbons towards diclofenac (DCF) from aqueous solution were 271, 522, 821, and 1033 mg/g, respectively. Hence, the adsorption capacities of ACs were considerably enhanced with the activation time, and F12, F24, and F40 carbons presented the highest adsorption capacities towards DCF reported in the technical literature. The F40 adsorption capacity was at least twice those of other carbon materials. The adsorption capacities decreased by raising the pH from 7 to 11 due to electrostatic repulsion between the ACs surface and anionic DCF in solution. The removal of DCF from a wastewater treatment plant (WWTP) effluent was effectively carried out by adsorption on F40. Hence, the capacity of ACs for adsorbing DCF can be optimized by tailoring the porous structure of ACs., This work was supported by Consejo Nacional de Ciencia y Tecnologia, CONACyT, Mexico (grants numbers INFR-2012-01-188381 and CB-2012-02-182779). COA and JBP thank the support of the Spanish MINECO (grant number CTM2014/56770-R).

This study investigated the adsorption of two endocrine-disrupting chemicals, bisphenol A (BPA) and S (BPS), from water using activated carbon clothes (ACCs), as-received and oxidized, in the absence and presence of bacteria, analyzing both kinetic and equilibrium adsorption data. Kinetic study of the different systems showed that the adsorption rate was affected both by the oxidation of the adsorbent and by the presence of bacteria. Bisphenol adsorption kinetics followed a second-order kinetic model, with rate constants between 0.0228 and 0.0013 g min−1 mol−1. ACC was a much better adsorbent of E. coli compared to granular activated carbons, achieving 100% adsorption at 24 h. ACC oxidation reduced the adsorption capacity and the adsorbent-adsorbate relative affinity due to the decrease in carbon surface hydrophobicity. Conversely, the presence of bacteria in aqueous solution increased the ACC surface hydrophobicity and therefore enhanced the adsorption capacity of BPA and BPS on ACC, which was 33% and 24%, respectively. In all cases, more BPS than BPA was removed due to the greater dipolar moment of the former. Results found show that activated carbon clothes in the presence of bacteria can be an adequate process to remove bisphenol A and S from different aqueous systems.

In this work, a series of carbon xerogel/graphene hybrids were synthesized from resorcinol and formaldehyde by adding increasing loadings of graphene oxide (GO) solution. Resulting samples were functionalized with urea and characterized by SEM, adsorption-desorption isotherms of N2 at 77 K, X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. Carbon xerogel/graphene hybrids were assessed as adsorbents for metronidazole (MNZ) removal in aqueous solutions under different operational conditions (solution pH, temperature, ionic strength, and type of water) to determine its adsorption mechanism. The maximum adsorption capacities (qm) of carbon xerogel/graphene hybrids towards MNZ were in the range of 110–166 mg g−1 at pH = 5 and 298 K. Moreover, the results showed almost a linear relationship between SBET and qm. The adsorption capacity of MNZ decreased at ionic strength lower than 0.01 N NaCl and remained constant at higher ionic strength. MNZ adsorption is not inhibited by the presence of ions in treated water and the process exhibited endothermic nature. Based on the obtained results from the adsorption equilibrium, the MNZ removal might occurred by different mechanism such as π-π dispersive interactions, attractive electrostatic interactions (at pH = 8), and hydrogen bonds., This work was financially supported by the projects RTI2018-099224-B-I00 funded by Spanish MICINN-FEDER and Consejo Nacional de Ciencia y Tecnología (National Council of Science and Technology), CONACyT, Mexico, through Grant No. 290817 and PN-2015-625. LMPM and SMT acknowledge the financial support from the Spanish MINECO for a Ramon y Cajal research contract (RYC-2016-19347) and University of Granada (Reincorporación Plan Propio), respectively.

This work is focused on the development of monolithic carbon xerogels-metal composites for oil removal through adsorption and regeneration processes from oil-in-saltwater emulsions. In this way, three carbon materials with and without metal content (Ni and/or Ce) were prepared by a sol-gel method, namely XCe (carbon xerogel with 18 wt% of cerium), XCeNi (carbon xerogel with 18 and 4 wt% of cerium and nickel, respectively), and X (free metal-carbon xerogel). Crude oil adsorption was tested by batch adsorption experiments, varying different operational conditions, including pH (2, 7, and 11), temperature (25, 35, and 45 °C), amount of monolithic composite (0.01, 0.1 and 0.3 M) and its nature. Regeneration studies were done through oxidation method using air in a thermogravimetric analyzer under isothermal (150, 200, and 250 °C) and non-isothermal conditions (100–600 °C). From N2 adsorption isotherms it was found that all materials presented a type Ib behavior distinctive of microporous materials. Adsorption results show that crude oil removal increased with the increase of metal content in the composite for all experimental setups. Also, crude oil decomposition was successfully assessed, obtaining the main decomposition peak at 150 °C during non-isothermal runs. For isothermal experiments, the three monolithic carbon xerogels achieved 100% conversion of the crude oil adsorbed for all temperatures, whereas raw crude oil only decomposed 60%. The catalytic activity of three monolithic carbon xerogels was corroborated with effective activation energy calculations, which was reduced by 24.9, 32.5, and 52.4% from virgin crude oil decomposition to decomposition adsorbed on the samples X, XCe, and XCeNi, respectively.

In this work the single and ternary removal of sulfonamides (sulfamethoxazole, sulfadiazine and sulfametazine) from water was investigated using granular activated carbon. The single adsorption mechanism was elucidated by obtaining the adsorption isotherms supported by computational calculations. The ternary adsorption was analyzed by using an experimental Box-Behnken type response surface design. The results showed that the total adsorption capacity of activated carbon duplicates in ternary systems compared to single systems. Besides, in both cases the activated carbon showed a greater affinity for removing sulfamethoxazole followed by sulfadiazine and sulfametazine, correspondingly. It was shown that hydrogen bonding interactions presented the highest adsorption energies followed by π-π interactions. From the design of experiments three statistically reliable mathematical models were proposed to estimate the adsorption capacity for each sulfonamide as a function of the solution pH, temperature and initial concentration. Finally, it was shown that sulfonamide ternary adsorption is an endothermic process and that the adsorption rate decreases as a result of partial blockage of the pores due to simultaneous adsorption.