Physisorption Process Research Articles

Synthesis of porous dimethoxypillar[5]arene knitted β-cyclodextrin copolymers for efficient adsorption of organic micropollutants

Herein, through knitting benzylated β-cyclodextrin (BnCD) by dimethoxypillar[5]arene (P[5]), porous copolymers (P[5]-BnCDs) containing two kinds of macrocycles were synthesized with yields not <97 %. The molar ratio of P[5]/BnCD greatly influenced the P[5]-BnCDs' porosity and adsorption performance. When the molar ratio of P[5]/BnCD was 4/1, the P[5]-BnCD (4-1), demonstrated a surface area up to 515.95 m2/g and showed fast adsorption kinetic, high adsorption capacity and good reusability towards the model organic micropollutants (OMPs). The adsorption fitted well with the pseudo-second-order and the Langmuir models, while the thermodynamic studies revealed spontaneous physisorption process. The adsorption mechanism was dominant by host-guest and hydrophobic interactions and the adsorption at environmentally relevant concentrations experiments showed the practicality and superiority in extraction of the OMPs at μg/L level. This study paves a way for the development of versatile porous organic polymers with multiple macrocycles for efficient removal of OMPs from water.

Simultaneous removal of As(V) and Pb(II) using highly-efficient modified dehydrated biochar made from banana peel via hydrothermal synthesis

Efficient removal of arsenic (As) and lead (Pb) from industrial wastewater has long been a critical environmental issue due to their serious risk to human health. Therefore, in this work, a modified banana peel biochar (MBPB) was prepared by mixing calcium nitrate, diammonium hydrogen phosphate, sulfuric acid, ferric nitrate with dehydrated banana peel biochar as adsorbent for As(V) and Pb(II) removal in wastewater, and their absorption mechanism was investigated. SEM-EDS, TEM, FTIR, XRD, XPS, BET, kinetic, and isothermal characteristics of MBPB and pristine banana peel biochar (PBPB) were conducted. The behavior of both metal ions on MBPB and PBPB was well explained by the pseudo-second-order kinetic with Langmuir and Freundlich models. We found that the two biochar’s behaviors were mixture processes of monolayer and multilayer adsorption, achieving maximum capacities as determined by the Langmuir model of 39.5 mg g−1 (MBPB-As), 33.2 mg g−1 (MBPB-Pb), 30.8 mg g−1 (PBPB-Pb), and 23.5 mg g−1 (PBPB-As), with maximum efficiencies of 98.7% (MBPB-As) and 90.3% (MBPB-Pb) under optimum conditions. Thermodynamic tests showed that As(V) and Pb(II) removal on MBPB was a spontaneous and endothermic physisorption process. MBPB showed great reusability in As(V) and Pb(II) removal, with removal rates as high as 71.4% and 66.5% after five cycles, respectively. Selective adsorption of As(V) and Pb(II) was also investigated on MBPB, and the removal rate was still high in the mixture of heavy metals. These findings provide a feasible method for the environmental-benign utilization of banana peel as a low-priced adsorbent in wastewater treatment.

Strong adsorption of CV dye by Ni ferrite nanoparticles for waste water purification: Fits well the pseudo second order kinetic and Freundlich isotherm model

This work focuses on the crystal violet (CV) dye removal from water by using prepared spherical and crystalline nickel ferrite nanoparticles (NiF-NPs) having cubic spinel phase with average size of 28 nm. The toxic, carcinogenic and mutagenic nature of CV dye along with long time persistence in the environment without degradation causes a major impact on living organisms and hence, the removal of CV dye from drinking water is necessary. The experimental batch adsorption data have been analyzed through Langmuir, Freundlich, Temkin and Dubinin-Radushkevich isotherm models. It is observed that the data fits well in the Freundlich isotherm model as correlation coefficient value (R2) is 0.985, which indicates formation of multilayer coverage over the surface of NiF nanoparticles. Again, Dubinin-Radushkevich's model has provided the adsorption energy (E) of CV dye as 1.629 (kJ/mol), which indicates that dye adsorption takes place through the physical-sorption process. Further, kinetic study indicates that the pseudo 2nd order model is suitable for adsorption data as equilibrium adsorption capacity has been found as 19.58 (mg/g) and R2 value as 0.998 with low value of rate constant (k2) as 0.019 (g mg−1 min−1). Further, R2 value for intra-particle diffusion model is obtained as 0.999, hence it is suitable for explaining the mechanism of adsorption process.

Adsorption of methane onto mudstones under supercritical conditions: Mechanisms, physical properties and thermodynamic parameters

Since the mechanisms of methane-mudstone interactions are important for estimating shale gas reserves, methane adsorption under supercritical conditions of 30 MPa pressure and 303.15, 333.15, 363.15 K temperatures was studied to measure the excess methane adsorption in two mudstone samples from Yanchang Formation, Ordos Basin. Excess adsorption features inflection points where the amount of adsorbed gas changes from increasing to decreasing concentrations. Three methods (fixed, slope, and freely fitted density) were applied to calculate the adsorbed-phase density ( ρ ad ), which was then used to fit the measured excess adsorption. Two criteria, the goodness-of-fit and whether the fitting can obtain reasonable absolute adsorption, were applied to determine the most accurate model. Results indicated that the supercritical Dubinin-Radushkevich ( SDR ) model with freely fitted ρ ad was the most reasonable model. The volume of adsorbed methane at 363.15 K is close to the micropore ( d < 2 nm) volume of the corresponding mudstone. Considering the actual geological conditions, the adsorbed gas should be predominantly stored in micropores. Thermodynamic parameters reveal that the methane adsorption on mudstone is a physisorption process that is jointly controlled by the heterogeneity of, and interaction forces between the methane molecule and, the rock surface.

Insight the mechanism of MgAl/layered double hydroxide supported on rubber seed shell biochar for Remazol Brilliant Violet 5R removal

The ever-increasing concentration of Remazol Brilliant Violet 5R discharged mainly from textile industry had cause serious environmental issues towards human and the surrounding ecosystem. Therefore, solving the issue related to dye contamination is seriously important. In this research study, MgAl/layered double hydroxide supported on rubber seed shell biochar (RSSB) had been prepared for Remazol Brilliant Violet 5R (RBV5R) dye adsorption. BET surface area and pore volume of RSSB were found to be 132.40 m2/g and 0.0732 cm3/g, respectively with presence of LDH metals on the RSSB surfaces. The batch adsorption studies showed that RBV5R uptake capacity was significantly enhanced (125.88 mg/g) compared to pristine RSSB (58.69 mg/g) at initial RBV5R concentration, contact time, adsorption temperature and pH of 300 mg/l, 1440 min, 60 °C and pH 2, respectively. The equilibrium and kinetic adsorption data were best fitted into the Freundlich and pseudo-first order model, respectively. The thermodynamic study confirmed the RBV5R adsorption was endothermic in nature and governed by physisorption process. All these findings signified that the MgAl/LDH-RSSB is a promising adsorbent for treating wastewater containing RBV5R dye.

Adsorption of Fatty Acid on Beta-Cyclodextrin Functionalized Cellulose Nanofiber

Fatty acids in wastewater contribute to high chemical oxygen demand. The use of cellulose nanofiber (CNF) to adsorb the fatty acids is limited by its strong internal hydrogen bonding. This study aims to functionalize CNF with β-cyclodextrin (β-CD) and elucidate the adsorption behaviour which is yet to be explored. β-CD functionalized CNF (CNF/β-CD) was achieved by crosslinking of β-CD and citric acid. Functionalization using 7% (w/v) β-CD and 8% (w/v) citric acid enhanced mechanical properties by increasing its thermal decomposition. CNF/β-CD was more efficient in removing palmitic acid, showcased by double adsorption capacity of CNF/β-CD (33.14% removal) compared to CNF (15.62% removal). CNF/β-CD maintained its adsorption performance after five cycles compared to CNF, which reduced significantly after two cycles. At 25 °C, the adsorption reached equilibrium after 60 min, following a pseudo-second-order kinetic model. The intraparticle diffusion model suggested chemical adsorption and intraparticle interaction as the controlling steps in the adsorption process. The maximum adsorption capacity was 8349.23 mg g−1 and 10485.38 mg g−1 according to the Sips and Langmuir isotherm model, respectively. The adsorption was described as monolayer and endothermic, and it involved both a physisorption and chemisorption process. This is the first study to describe the adsorption behaviour of palmitic acid onto CNF/β-CD.

Enhancement of oxygen adsorption using biomass-based oxidized porous carbon

The porous carbon adsorbent walnut-shell precursors-based biomass using the Hummer synthesis method was developed for oxidized porous carbon adsorbent. Adsorption-desorption of N2, high-resolution transmission electron microscopy (HRTEM), FESEM, FTIR spectra, and X-ray powder diffraction analyses were used to evaluate the morphology and structure of the specimens. The oxidized porous carbon adsorbent possessed a specific surface area (217.34 m2/g) and pore volume (0.1524 cm3/g). The oxidization process reduced the average volume of mesopores and micropores. Although the specific surface area of the oxidized sample was reduced, the oxygen adsorption capacity was improved by more than 1.4 times. Under 298 K and 9.55 bar pressure, the greatest adsorption capacities for oxygen and nitrogen were specified to be 4.11 (mmol/g) and 3.03 (mmol/g), respectively. The oxygen and nitrogen adsorption on the porous carbon closely was matched by the Fractional-order kinetic and Sips isotherm models, and thermodynamic analysis demonstrated that the physisorption process was confirmed. The improved adsorbent's oxygen adsorption selectivity was remarkable. Oxygen and nitrogen adsorption were increased by oxidized adsorbent by 40% and 14%, respectively. Ultimately, oxygen can be adsorbed by the oxidized sample with more efficiency than nitrogen gas.

One-pot removal of pharmaceuticals and toxic heavy metals from water using xerogel-immobilized quartz/banana peels-activated carbon

ABSTRACT Here, we report the efficient one-pot removal of heavy metal ions and pharmaceuticals using xerogel, activated carbon and gravel. The simplest xerogel from tetramethyl orthosilicate showed ∼ twice the adsorption capacity of activated carbon derived from banana peels at 600 °C and far greater (x 35) than quartz pellets of diameter ∼300 μm. Functional groups present in both xerogel and activated carbon greatly enhanced the adsorption process. The combination of the three adsorbents resulted in the removal of > 95% of heavy metal ions and pharmaceuticals from water. The data fitted well in linear equations of Langmuir and Freundlich adsorption isotherms, and pseudo-first-order and pseudo-second-order kinetics, an indication for physisorption, chemisorption, adsorption and desorption processes during pollutant capture by the adsorbents.

Synthesis of K+ and Na+ Synthetic Sodalite Phases by Low-Temperature Alkali Fusion of Kaolinite for Effective Remediation of Phosphate Ions: The Impact of the Alkali Ions and Realistic Studies

Two sodalite phases (potassium sodalite (K.SD) and sodium sodalite (Na.SD)) were prepared using alkali fusion of kaolinite followed by a hydrothermal treatment step for 4 h at 90 °C. The synthetic phases were characterized as potential adsorbents for PO43− from the aqueous solutions and real water from the Rákos stream (0.52 mg/L) taking into consideration the impact of the structural alkali ions (K+ and Na+). The synthetic Na.SD phase exhibited enhanced surface area (232.4 m2/g) and ion-exchange capacity (126.4 meq/100 g) as compared to the K.SD phase. Moreover, the Na.SD phase exhibited higher PO43− sequestration capacity (Qmax = 261.6 mg g−1 and Qsat = 175.3 mg g−1) than K.SD phase (Qmax = 201.9 mg g−1 and Qsat = 127.4 mg g−1). The PO43− sequestration processes of both Na.SD and K.SD are spontaneous, homogenous, and exothermic reactions that follow the Langmuir isotherm and pseudo-first-order kinetics. Estimation of the occupied active site density validates the enrichment of the Na.SD phase with high quantities of active sites (Nm = 86.1 mg g−1) as compared to K.SD particles (Nm = 44.4 mg g−1). Moreover, the sequestration and Gaussian energies validate the cooperation of physisorption and weak chemisorption processes including zeolitic ion exchange reactions. Both Na.SD and K.SD exhibit significant selectivity for PO43− in the coexisting of other common anions (Cl−, SO42−, HCO3−, and NO3−) and strong stability properties. Their realistic application results in the complete adsorption of PO43- from Rákos stream water after 20 min (Na. SD) and 60 min (K.SD).

Evaluation of the Environmental Performance of Adsorbent Materials Prepared from Agave Bagasse for Water Remediation: Solid Waste Management Proposal of the Tequila Industry.

In the present research work, the use of agro-industrial waste such as agave bagasse from the tequila industry was carried out. The agave bagasse was treated to obtain biosorbent and hydrochar materials. Direct Blue 86 was used as an adsorbate model to evaluate the performance of both materials. The adsorption studies showed an adsorption capacity of 6.49 mg g−1 in static and 17.7 mg g−1 in dynamic, associated with a physisorption process between functional groups of the material and the dye. The characterization of the biosorbent showed that the material was mainly composed of macroporous fibers with a surface area <5.0 m2 g−1. Elemental analysis showed a majority composition of C (57.19 wt%) and O (37.49 wt%). FTIR and XPS analyses showed that the material had C-O, C=O, -OH, O-C=O, and -NH2 surface groups. RAMAN and TGA were used to evaluate the composition, being cellulose (40.94%), lignin (20.15%), and hemicellulose (3.35%). Finally, the life-cycle assessment at a laboratory scale showed that the proposed biosorbent presents a 17% reduction in several environmental aspects compared to hydrochar, showing promise as an eco-friendly and highly efficient method for the remediation of water contaminated with dye, as well as being a promising alternative for the responsible management of solid waste generated by the tequila industry.

Influence of extraction techniques on the adsorption capacity of methylene blue on sawdust: Optimization by full factorial design

Wood wastes have been widely studied for their adsorption properties in recent years. Researchers have mainly been interested in Atlas cedar sawdust. The present work studies four adsorbents after different extraction (hydrodistillation, soxhlet, maceration, and ultrasound) for methylene blue adsorption. The points discussed concern the operating conditions used during adsorption, thermodynamic, kinetic and other models describing the adsorbent-adsorbate system, and the effect of the main operating parameters (adsorbate concentration, treatment pH, and adsorbent concentration) was investigated using the full factorial design. The best adsorbent is the residue of sawdust generated after extraction via maceration: the yield of methylene blue adsorption is 98.42 % and the adsorbed quantity (Qads = 7.84 mg/g) is close to that of powdered activated carbon used for comparison (Qads = 9 mg/g). According to the kinetic result, the second order describes well the adsorption of MB onto the four types of Cedar Sawdust. The thermodynamic study confirms the physisorption process in which the enthalpy was found low to 40 kJ·mol−1.

Sodium Succinate as a Corrosion Inhibitor for Carbon Steel Rebars in Simulated Concrete Pore Solution.

The inhibiting performance of sodium succinate (Na2C4H4O4) was evaluated as an organic environmentally friendly corrosion inhibitor for carbon steel rebars in 0.6 M Cl- simulated concrete pore solution. Potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) measurements were utilized to evaluate the inhibitor performance at different temperatures and concentrations. The investigated corrosion inhibitor showed strong corrosion inhibition performance as it adsorbs on the surface of the rebar, creating a protective adsorption film. According to PDP, the inhibitor is classified as a mixed-type inhibitor with an inhibitor efficiency of 77, 69, 59, and 54% for 25, 35, 45, and 55 °C, respectively. EIS validated the PDP tests, showing that sodium succinate displaces the water molecules at the interface, creating an adsorption film by complexing with ferrous ions. The film thickness was calculated, and sodium succinate was able to produce a thicker protective film (span of nanometers) relative to the reference at every temperature. The adsorption of sodium succinate follows the Temkin adsorption isotherm. ΔG0ads was found to be -32.75 kJ/mol, indicating that the inhibitor adsorption is a combined physisorption and chemisorption process. Different surface characterizations were utilized to substantiate the adsorption of sodium succinate, these include scanning electron microscopy, energy-dispersive X-ray spectroscopy, and micro-Raman spectroscopy. Finally, quantum chemical calculations showed that the delocalized electrons in the carboxyl group have high HOMO energies and electrostatic potential, which facilitates the adsorption of sodium succinate corrosion inhibitor onto the carbon steel rebar surface.

A facile synthesis of ternary hybrid nanocomposite of WS2/ZnO/PPy: An efficient photocatalyst for the degradation of chromium hexavalent

In this study novel and promising ternary hybrid nanocomposite of tungsten disulphide (WS2), zinc oxide (ZnO) and polypyrrole (PPy) has been synthesized for the efficacious photocatalytic reduction of hexavalent chromium (Cr(VI)). This ternary hybrid nanocomposite was prepared using the hydrothermal and in situ oxidative polymerization method. The crystal structures, physicochemical and optical features of the prepared nanocomposite were examined using various characterization techniques such as XRD, FTIR, and UV–Vis spectroscopy. The synthesized nanocomposite contains the morphologies of pristine samples such as nanosheets, nanorods and nanoparticles of WS2, ZnO and PPy, respectively as demonstrated from FESEM images. The adsorption and photocatalytic degradation studies were performed as a function of concentrations of Cr (VI). The synthesized nanocomposite shows enhanced degradation efficiency (81.82%–94.66%) from pristine samples (1.81–4.85% for WS2, 29.09–36.36% for ZnO and 45.55–48.94% for PPy) towards 10 mg/L concentration of Cr(VI) under dark and light conditions, respectively. This enhanced degradation efficiency was attributed to the large surface area, lower recombination rate for photogenerated species, superior absorption for light and generation of free radicals under dark and light conditions as explained by TCSPC decay, tauc's plot (2.28 eV) and EPR measurements, respectively. EPR and scavenger study both supports for the formation of free radicals (•O2−) and (.OH) in light and dark both conditions. The value of g-factor comes out to be 2.01 from EPR study. The kinetic study illustrates that the photocatalytic degradation of Cr(VI) by the prepared ternary nanocomposite followed pseudo-second-order rate kinetics model and Langmuir adsorption isotherm. These models proposed that the removal of Cr(VI) was take place through both physisorption and chemisorption processes. The degradation mechanism was analyzed with the help of Mott-Schottky/scavenger studies, and revealed that the superoxide radicals (•O2−) were the primary active species. The reusability experiment demonstrates that the prepared nanocomposite can be reused up to 5 times with almost the same efficiency in all cycles and hence, can be considered as a promising candidate for wastewater treatment.

Functionalized graphene oxide-zinc oxide hybrid material and its deployment for adsorptive removal of levofloxacin from aqueous media

This work reports on the synthesis of aspartic acid-functionalized graphene oxide-zinc oxide, as a functional porous material, and its potential to mitigate levofloxacin (LFXN). The adsorbent was characterized by various techniques, including ultraviolet–visible (UV–Vis), Fourier transform infrared (FT-IR) spectroscopy, powder X-ray diffraction (PXRD), and scanning electron microscopy (SEM). The average crystallite size of the prepared composite was about 17.30 nm. Batch adsorption studies were carried out to elucidate the adsorption process for LFXN. Different parameters, including contact time, LFXN initial concentration, adsorbent concentration, pH, temperature, and ionic strength were studied. The mechanism and kinetics were studied by fitting the data to Freundlich and Langmuir isotherms, pseudo-first-order and pseudo-second-order kinetic models, respectively. The isotherm data was better fitted to Langmuir isotherm (R2 = 0.999) as compared to the Freundlich model. The maximum adsorption capacity obtained at equilibrium was 73.15 mg/g. For kinetic studies, Pseudo first order was better fitted with R2 = 0.87797, confirming the physisorption process. Thermodynamics parameters revealed that the process was exothermic and spontaneous at low temperatures. The adsorption mechanism was studied and the impregnation of LFXN in the adsorbent was confirmed by FTIR studies. This research proved that the designed GO/Asp-ZnO was a novel and promising adsorbent for the removal of LFXN with an efficiency of 95.12% at 30 mg/L LFXN by 0.6 g/L adsorbent in 24 h at pH = 7 and T = 25 °C.

Improved Catalytic Performance of Lipase Eversa® Transform 2.0 via Immobilization for the Sustainable Production of Flavor Esters—Adsorption Process and Environmental Assessment Studies

The aim of this study was to produce several flavor esters via esterification of octanoic acid with different commercial short-chain alcohols (methanol, propanol, isoamyl alcohol, hexanol and benzyl alcohol) and fusel oil in solvent-free systems. Lipase Eversa® Transform 2.0 immobilized via mechanism of interfacial activation on poly(styrenene-divinylbenzene) (PSty-DVB) beads was used as heterogeneous biocatalyst and its catalytic performance was compared with that of the soluble lipase. The heterogeneous biocatalyst was prepared by employing 5 mmol·L−1 buffer sodium acetate at pH 5.0 and 25 °C using an initial protein loading of 40 mg·g−1. The maximum amount of immobilized protein reached was 31 mg·g−1, corresponding to an immobilization yield of 80%. Mass transfer studies demonstrated that the lipase was preferentially adsorbed inside the pores of the support, which was confirmed by scanning electron microscopy analysis. Lipase immobilization can be described by a pseudo-first-order kinetic model via a physisorption process. When used as biocatalysts of the target reactions, the highest conversion percentage (between 65% and 85% of acid conversion after 60–90 min of reaction) values were achieved for esterification reactions catalyzed by immobilized lipase. Reusability tests revealed high retention of the original activity of the immobilized lipase after six successive batch reactions using isoamyl alcohol (47%) and fusel oil (72%). The proposed reaction systems can be considered green processes (EcoScale score above 80), with exception of methanol medium, classified as an acceptable green process (EcoScale score of 68). These results show that the heterogeneous biocatalyst prepared can be an economic and sustainable option for flavor esters production on an industrial scale.

Influence of regeneration conditions on cyclic CO2 adsorption on NaA zeolite at high pressures

This work aimed to determine the influence of different regeneration conditions on CO2 adsorption on NaA zeolite at high pressures through cyclic processes. To reach this goal, NaA characterization, high-pressure adsorption isotherms, heat of adsorption and working capacities for CO2/NaA system were performed. NaA zeolite characterization showed a high crystalline and stable microporous structure with 0.43 nm pore diameter and 247 m² g-1 specific area. CO2 adsorption isotherms are strongly favorable, showing adsorption uptakes equal to 4.73, 4.54 and 4.44 mol kg-1 (c.a. 20 wt%) at 40 bar and 20, 30 and 40 °C, respectively. Jensen-Seaton model fits experimental data and was used to determine CO2/NaA heats of adsorption from 10 to 40 kJ mol-1, which are characteristic of physisorption process. This was corroborated by constant working capacity for all regeneration processes, reaching 1.44, 3.27, and 4.27 mol kg-1 for REG-1 (1 bar, 30 °C), REG-2 (vacuum, 30 °C) and REG-3 (vacuum, 150 °C) regeneration processes, respectively. The working capacity simulation showed a strong influence of pressure and practically insensitive to adsorption temperature from 20° to 40°C. Therefore, NaA zeolite is a regenerative material showing a high potential for utilization in high pressure cyclic adsorption processes, such as fixed and fluidized beds, for CO2 separation when pressure and temperature are changed in blowdown/regeneration step.

Theoretical study of the olfactory perception of floral odorant on OR10J5 and Olfr16 using the grand canonical ensemble in statistical physics approach

In this work, two experimental dose-response curves of lyral molecules on the OR10J5 and the Olfr16 were employed in order to examine the evolution of physico-chemical parameters involved in the selected statistical physics model(s) to investigate the human and the mouse smelling of a floral scent. Indeed, one layer adsorption model on one type of sites with one energy (1LAM1T1E) and one layer adsorption model on two types of sites with two energies (1LAM2T2E), considered as appropriate models for the adsorption of lyral molecules on the OR10J5 and Olfr16, respectively, have been applied to fit the experimental data. Stereographic and energetic physico-chemical parameters, namely: the maximum response(s) at saturation, the number of docked molecules per olfactory receptor binding site and the concentration(s) at half saturation, were investigated to retrieve helpful information to describe the adsorption process putatively introduced in the olfaction perception. Thus, the advanced modeling results indicated that the studied molecules were docked with a non-parallel orientation (n > 1). Furthermore, for the two olfactory systems, the molar adsorption energies estimated from curves modeling were inferior to 11 kJ/mol, which showed the physisorption process of the adsorption of lyral molecules on OR10J5 and Olfr16. The 1LAM2T2E and the 1LAM1T1E were applied to estimate the OR10J5 and the Olfr175 RSDs, respectively. Hence, lyral RSDs were spread out from 0.7 to 20 nm with maximums at about 4 nm for OR10J5 and at about 3.65 nm for Olfr16. In addition, by using the two advanced models, the olfactory responses of lyral on OR10J5 and Olfr16 can be used for the energetic characterization of the lyral-OR10J5/Olfr16 binding sites interactions and allowed access to the adsorption energy distributions (AEDs). Then, two approximate olfactory bands can be determined for lyral molecules docked on OR10J5 and Olfr16, which are defined between 3 and 15.5 kJ/mol and between 3.5 and 13.5 kJ/mol, respectively. Lastly, thanks to the proposed models the adsorption entropy of the studied systems can be calculated to describe the disorder and the order on OR10J5 and Olfr16 surfaces (disorder peak of the two olfactory systems was attained when the equilibrium concentration was equal to the concentration at half saturation). Furthermore, the Gibbs free enthalpy and the internal energy were estimated and their negative values indicated that the adsorption phenomenon involved in the olfactory perception was spontaneous and exothermic nature.

Thermodynamic, Nonlinear Kinetic, and Isotherm Studies of Bisphenol A Uptake onto Chemically Activated Carbons Derived from Safou (Dacryodes edulis) Seeds

The interest of this work is to evaluate the possibility of using safou seeds to develop a new low-cost adsorbent and study its application to remove bisphenol A from an aqueous solution for a sustainable and ecological use of this biomass. This was done by optimizing some parameters that influence the adsorption process. The central composite design with four centre points was used to optimize the process variables. The concentration of bisphenol A solution, adsorbent dosage, stirring time, and solution pH on the adsorption capacity were considered, while the response measured was the quantity adsorbed. The activated carbon obtained by treatment with H2SO4 was named NSST and that obtained by treatment with H3PO4 was named NSPT. XRD revealed an amorphous character for the ACs, and EDXS showed they are mainly carbonaceous. Under the optimal adsorption conditions, NSPT showed the best performance. Correlation coefficients R2 and R2adj were of 85.13 and 69.12% for NSPT and 83.71 and 66.17% for NSST. A pseudo-second-order nonlinear kinetic model best described the adsorption kinetic of BPA removal by the ACs. Langmuir’s isotherm best described the adsorption of BPA onto both adsorbents. Thermodynamic studies suggested an exothermic and physisorption process.

Microwave-induced fabrication of fiber-reinforced adsorbent from waste cardboard and chitosan for effective dye removal

An adsorption process is a familiar approach to the dye decontamination of polluted wastewater. Ecological and low-cost fabrication of a highly efficient adsorbent has been a typical predicament. Herein, we reported a microwave-assisted preparation of a waste-based three-dimensional fibrous material with reliable mechanical stability, efficient adsorbing characteristics, and excellent dye decontamination performance. The material was prepared by reinforcing the milled waste cardboard fibers using chitosan to establish dual-pore scaffolds composed of interconnected lamellar channels and random pores. The adsorbent demonstrated exceptional removal capacity for the dye solution which fitted well with the isotherm model of Langmuir and the thermodynamic analysis of the adsorption process verified the prominent physisorption process. The maximum removal efficiency of the obtained samples for 25 ppm dye solution was up to 99% at a maximum adsorption capacity of 53.87 mg g−1. It is also worth mentioning that m(CF/Ch-2)7 has consistent removal performance over multiple cycles of regeneration. These results featured to be a promising material for utilizing solid waste materials to address one major type of water pollution.

Industrial steel waste-based adsorbent: An effective phosphate removal from aqueous media

This work offers the alternative to mitigate the problem of eutrophication of water bodies that can result in a serious threat to environment and aquatic life by using steel wastes for phosphate removal. Produced on the scale of thousands of tons per year, these wastes can contribute to air, soil, and water pollution when discharged without a proper management. In this context, this work evaluates the potential of phosphate remediation by adsorption applying steel industry wastes, addressing two important environmental problems at once. For the first time, blast furnace sludge (BFS) and the powder from Kanbara reactor (KR) without pre-treatment were used for the elucidation of the removal mechanism of phosphate, employing the method of sequential extractions, kinetic studies, and thermodynamics. The chemical and structural analyses demonstrated the materials present an irregular morphology with most of the pores in the mesopore range being mainly composed by alkali metals and metal oxides. Although approximately 99% of phosphate removal efficiency was reached for both wastes in 24 h, the speciation studies showed phosphate and KR interacts too strongly making its reuse hardly feasible and therefore not suitable from a practical point of view. For BFS, on the contrary, the thermodynamic data indicated a physisorption process offering the advantage of reutilization. In addition, about 97% of phosphate removal is achieved during the first 10 min of adsorption, regardless the solution pH, thus offering good prospects in aggregating value to steel industry wastes as adsorbents being in line with a sustainable economy.