Liquid Film Diffusion Model Research Articles

Biosorption of Cr(VI) by Theobroma cacao pericarp.

This paper reports a comprehensive study of Theobroma cacao pericarp (TCP) residues, which has been prepared, characterized, and tested as an inexpensive and efficient biosorbent of Cr(VI) from aqueous solutions. The maximum adsorption capacity of TCP obtained at optimal conditions (pH = 2, dose = 0.5g L-1, C0 = 100mg L-1) was qmax = 48.5mgg-1, which is one of the highest values reported by the literature. Structural and morphological characterization has been performed by FTIR, SEM/EDX, and pHPZC measurements. FTIR analysis revealed the presence of O-H, -NH, -NH2, C = H, C = O, C = C, C-O, and C-C functional groups that would be involved in the Cr(VI) biosorption processes. The experimental equilibrium data of biosorption process were successfully fitted to non-linear Langmuir (R2 = 0.95, χ2 = 11.0), Freundlich (R2 = 0.93, χ2 = 14.8), and Temkin (R2 = 0.93, χ2 = 14.7) isotherm models. Kinetics experimental data were well adjustment to non-linear pseudo-2nd (R2 = 0.99, χ2 = 2.08)- and pseudo-1st-order kinetic models (R2 = 0.98, χ2 = 2.25) and also to intra-particle Weber-Morris (R2 = 0.98) and liquid film diffusion (R2 = 0.99) models. These results indicate that Cr(VI) biosorption on heterogeneous surfaces as well as on monolayers of TCP would be a complex process controlled by chemisorption and physisorption mechanisms. The thermodynamic results indicate that the Cr(VI) biosorption on TCP is a feasible, spontaneous, and endothermic process. TCP can be regenerated with NaOH and reused up to 3 times.

The Bioremoval of Toxic Dyes Using Chlorella Algae in Airlift Bioreactor

<p style="text-align:justify; margin-bottom:11px"><span style="font-size:11pt"><span style="line-height:107%"><span style="font-family:Calibri,sans-serif"><span style="font-size:14.0pt"><span style="line-height:107%"><span style="font-family:"Times New Roman",serif">Malachite green (MG) and Crystal Violet (CV) are used mainly as dyestuff and antimicrobials in aquaculture. They have a severe toxic effect on the environment. Several techniques were used to remove impurities from an aqueous solution: chemical, physical, and electrical. Among all these techniques, using dry algae is a more economical and helpful process. This study aims to investigate using an airlift reactor in the removal of MG and CV by chlorella algae as a biosorbent under different variables. The experiments were carried out in an airlift bioreactor. The experiments were carried out under the effect different operating conditions of initial dye concentration (5-40 ppm), alga dosage (0.3-1.8 gm/l), pH (3–10), air flow rate (0-40 ml/min), temperature (298-318 K) and contact time (5-60 min).  The results show that the introduce of air bubbles significantly enhances the removal efficiency of the dye. The best removal effectiveness was 95.2% for MG dye and 96.1% for CV dye.  The thermodynamics results reveal that the processes are exothermic for both dyes. Kinetic and adsorption isotherms results show the best fit is pseudo-second order and Langmuir model. The mass model result shows that the liquid film diffusion model was the best-fitted for both dyes.</span></span></span></span></span></span></p>

Comprehensive analysis of cationic dye removal from synthetic and industrial wastewater using a semi-natural curcumin grafted biochar/poly acrylic acid composite hydrogel.

Polymer composites offer a tailored framework as an exceptional candidate for water treatment due to their tunable chemical structure, porous 3D architecture, physiochemical stability, accessibility, pH-sensitivity and ease of use. In this study, curcumin-engineered biochar is embedded into a cross-linked polyacrylic acid hydrogel matrix using in situ polymerization for developing a semi-natural adsorbent for the removal of cationic dye from an aqueous solution. The physicochemical features of the generated composite hydrogel are significantly influenced by the implementation of curcumin-grafted biochar into the polyacrylic acid substrate. Comprehensive characteristic approaches were employed to explore all aspects of the adsorbent's properties, especially its removal efficacy. The methodical adsorption study was accomplished by monitoring dynamic factors such as pH, adsorbent content, time frame, and initial dye concentration. The presence of the porous aromatized structure of biochar, active oxygen-enrich functional groups (carboxyl, hydroxyl, keto, enol, ether) coupled with the conjugated curcumin structure facilitate the effective establishment of hydrogen bonds, electrostatic interactions, π-π interactions, electron donor-acceptor and charge-assisted H-bonding with the malachite green (MG) and rhodamine B (Rho) molecules. The highest adsorption capacities of MG and Rho reached 521 mg g-1 and 741 mg g-1 respectively, in the range of neutral pH, considering their molecular nature, functionalities, and unique adsorption mechanisms. The isothermal modeling was carried out with Henry, Langmuir, Jovanovic, Freundlich, Temkin, and Koble-Corrigan models to determine the adsorption system. Additionally, the kinetic data were assessed with Bangham, pseudo-first-order, pseudo-second-order, intra-particle, and liquid film diffusion models to ascertain the rate-limiting phase. The Koble-Corrigan and Langmuir isotherm models (R2 > 0.997) as well as pseudo-second-order (R2 > 0.998) and Elovich (R2 = 0.983 and 0.995) kinetics models provide a substantial level of concordance with empirical findings. The analysis of non-linear diffusion models revealed that the Bangham (R2 > 0.995) pore and liquid film diffusion (R2 > 0.960) models has major influence on the rate of the adsorption procedure. The binary adsorption test demonstrated higher efficacy of the synthesized adsorbent in the removal of malachite as compared to rhodamine. This study sheds light on the design of a cost-effective semi-natural polymeric composite for treating dye-polluted wastewaters, a major milestone toward environmental and ecological sustainability.

Simultaneous removal of triadimefon and dinotefuran by a new biochar-based magnesium oxide composite in water: Performances and mechanism

In recent years, the ecological security has been seriously threatened by the residues of pesticides in the environment. In this study, a new biochar-based magnesium oxide composite (MTBC) was successfully prepared using Traditional Chinese Medicine residues and MgCl2 solution, and then applied for the removal of triadimefon (TDF) and/or dinotefuran (DIN) in water. Batch experiments results indicated that 86.42 and 87.86 % of TDF and DIN removals could be obtained by MTBC within 120 min, respectively. The TDF adsorption process was proved to be well fitted with the pseudo-second-order kinetic, Elovich, liquid film diffusion, Intra-particle diffusion and Langmuir isothermal models. The TDF adsorption by MTBC was a spontaneous endothermic reaction, and chemical adsorption process was dominant. The inhibitory of the coexisting anions on TDF removal followed the order of SO42−＜Cl−＜HPO43−＜HCO3–. Both TDF and DIN could be simultaneously removed by MTBC at the certain concentrations levels. The possible removal mechanism for the adsorption of TDF and DIN by MTBC was proposed, both TDF and DIN were rapidly distributed and adsorbed on MTBC surface, then diffused into the interior pores structure and were finally adsorbed on MTBC through various reaction processes. The TDF removal process might be involved with hydrogen bonding, π-π interaction, pore filling and electrostatic interaction, while DIN removal might be involved with hydrogen bonding, pore filling and electrostatic interaction. These findings suggested that biochar-based magnesium oxide composite was an effective adsorbent for the remediation of agricultural effluents containing TDF and DIN.

Adsorption of BEZAKTIV BLAU V3-R and BEZAKTIV BLAU S-2R reactive dyes onto rice husk modified by the circular economy concept

Rice husk, modified with effluent from the alkaline scouring of cotton, employing an inexpensive treatment based on the circular economy concept, is used as a bio-sorbent to study the equilibrium and kinetic on cold brand BEZAKTIV BLAU V3-R (BBV3-R) and medium brand BEZAKTIV BLAU S-2R (BBS2-R) reactive dyes. 10, 20, and 40 g L−1 rice husk is used to follow adsorption of 0.1, 0.2, 0.3, 0.4, and 0.5 g L−1 BBV3-R and BBS2-R in a presence of 60 g L−1 NaCl at pH 10, at the temperature of 25 °C and 40 °C, respectively. Langmuir, Freundlich, and Dubinin-Radushkevic's adsorption models were employed, with the Freundlich model proving the best fit for our data. Activation energy calculated with the Dubinin–Radushkevic model (lower than 8 kJ mol−1) confirms the physical sorption of these reactive dyes onto the husk. The obtained maximum experimental absorption capacities of 122.2 mg g−1 for BBV3-R and 171.7 mg g−1 for BBS2-R using 10 g L−1 ERH are the best found in the literature. Pseudo-second-order model determines the adsorption kinetics, while the liquid film diffusion model is rate-determining. This paper demonstrates the applicability of the circular economy concept to obtain an efficient adsorbent for purifying colored effluent enriched with reactive dyes, which are one of the most challenging dyes in the textile industry from the aspect of their effluent purifying.

Potassium Hydroxide Activation as an Adsorbent for Kinetic Models of Hexavalent Chromium Adsorptions onto <i>Garcinia mangosteen</i> Shell

The utilized adsorption kinetic models, i.e., pseudo-zero order, pseudo-first-order, pseudo-second order, intraparticle diffusion, Bangham’s pore diffusion, liquid film diffusion, modified Freundlich and Elovich models have been cultivated the hexavalent chromium adsorption process. A high correlation coefficient (R2) and a small residual root mean square error (RMSE) and Chi-square (χ2) can be depicted in the pseudo-first order for the kinetic adsorption process of hexavalent chromium adsorption on the activated mangosteen shell with potassium hydroxide and carbonized at 400 °C for 2 h as a biochar adsorbent which has a specific surface area of 164 m2/g.

The Effect of Lithium Ion Leaching from Calcined Li-Al Hydrotalcite on the Rapid Removal of Ni2+/Cu2+ from Contaminated Aqueous Solutions.

A layered double hydroxide (LDH) calcined-framework adsorbent was investigated for the rapid removal of heavy metal cations from plating wastewater. Li-Al-CO3 LDH was synthesized on an aluminum lathe waste frame surface to prepare the sorbent. The calcination treatment modified the LDH surface properties, such as the hydrophilicity and the surface pH. The change in surface functional groups and the leaching of lithium ions affected the surface properties and the adsorption capacity of the heavy metal cations. A zeta potential analysis confirmed that the 400 °C calcination changed the LDH surface from positively charged (+10 mV) to negatively charged (-17 mV). This negatively charged surface contributed to the sorbent instantly bonding with heavy metal cations in large quantities, as occurs during contact with wastewater. The adsorption isotherms could be fitted using the Freundlich model. The pseudo-second-order model and the rate-controlled liquid-film diffusion model successfully simulated the adsorption kinetics, suggesting that the critical adsorption step was a heterogeneous surface reaction. This study also confirmed that the recovered nickel and/or copper species could be converted into supported metal nanoparticles with a high-temperature hydrogen reduction treatment, which could be reused as catalysts.

Adsorption Kinetics of Methyl Orange from Model Polluted Water onto N-Doped Activated Carbons Prepared from N-Containing Polymers.

This study aimed to assess the role of polymeric sources (polypyrrole, polyaniline, and their copolymer) of nitrogen (N)-doped activated carbons (indexed as PAnAC, PPyAC, and PnyAC, respectively) on their adsorption efficiency to remove methyl orange (MO) as a model cationic dye. The adsorbents were characterized using FTIR, SEM, TGA, elemental analysis, and surface area. The kinetic experiments were performed in batches at different MO concentrations (C0) and adsorbent dosages. The adsorption kinetic profiles of pseudo-first-order, pseudo-second-order (PSO), Elovich, intraparticle diffusion, and liquid film diffusion models were compared. The results showed a better fit to the PSO model, suggesting a chemisorption process. The adsorption capacity (qe, mg/g) was found to have increased as MO C0 increased, yet decreased as the adsorbent quantity increased. At the adsorption operating condition, including MO C0 (200 ppm) and adsorbent dose (40 mg), the calculated qe values were in the order of PAnAC (405 mg/g) > PPyAC (204 mg/g) > PnyAC (182 mg/g). This trend proved the carbon precursor's importance in the final properties of the intended carbons; elemental analysis confirmed that the more nitrogen atoms are in the activated carbon, the greater the number of active sites in the adsorbent for accommodating adsorbates. The diffusion mechanism also assumed a rate-limiting step controlled by the film and intraparticle diffusion. Therefore, such an efficient performance may support the target route's usefulness in converting nitrogenous-species waste into valuable materials.

Ficus Benjamin's leaf, a native sorbent for the exclusion of Methyl violet 10B from aquatic media

Due to the use of non-recyclable materials and the high costs of the technologies, removal of dyes from wastewater is becoming more and more pricey. This paper presents the capacity of Ficus Benjamina (FB) leaf powder to eradicate methyl violet dye 10 B (MV) in an aqueous fluid. The surface characteristics and presence of various functional groups on the surface of sorbent were revealed by SEM and FTIR studies. Diverse constraints on the elimination of methyl violet 10 B in an aqueous environment were also studied, including starting dye concentration, temperature, and contact duration. The Elovich & liquid film diffusion models, along with Lagergren first-order, pseudo-second-order, Bangham, and modified Freundlich modeling operated to assess kinetics. Experiments confirmed the pseudo-second-order concept. To investigate tentative data, multiple linear Langmuir, Freundlich, Temkin, as well as two parameters nonlinear isotherm models were applied, with findings indicating that sorption data were like both linear and non-linear isotherms. Sorption data were found to be in excellent agreement with the Freundlich isotherm with R2 value (0.99). The sorption capacity of the sorbent was computed i.e. 312.2 mg/g. Thermodynamic characteristics were also computed. It was concluded that the sorption of methyl violet 10 B sorption on FB leaf powder is exothermic. Hence, it is a potentially cost-effective bio sorbent for exclusion of dye from wastewater.

Adsorption and immobilization of phosphorus from eutrophic seawater and sediment using attapulgite - Behavior and mechanism

The adsorption behavior of phosphorus on raw sediment (RS), attapulgite (AT), purified attapulgite (PAT) and AT/PAT-amended sediments conforms to the Langmuir, pseudo first-order kinetics and liquid film diffusion model. The adsorption process is spontaneous and monolayer adsorption, and the adsorption rate is mainly controlled by liquid film diffusion. The addition of attapulgite improved the adsorption capacity of phosphorus in the sediments of mariculture ponds. The results of long-term sediment core incubation showed that the average reduction rates of total phosphorus (TP) and soluble reactive phosphorus (SRP) in overlying water and SRP in pore water by adding 20% purified attapulgite (S/PAT20) were 62.11%, 70.83% and 56.32% respectively, and the phosphorus flux in sediments decreased by 53.81%. The addition of attapulgite reduces the risk of phosphorus release in sediments, and changes sediments from “source” to “pool”. The specific surface area and pore volume of PAT increased to 203.254 cm2/g and 0.395 cm3/g respectively, but the phosphorus adsorption capacity was only increased by 2 times compared with AT (1431.3–2671.8 mg P/kg), indicating that the changes of mineral structure and chemical composition jointly determine the phosphorus adsorption effect. Adsorption mechanisms include physical adsorption, surface chemical precipitation, ligand effects, electrostatic attraction and ion exchange. Therefore, seeking modification methods with low energy consumption, low production cost, no damage to rod crystal, expansion of pore volume, increase of hydroxyl and other functional groups, and great retention of effective components are issues that need to be considered to improve the phosphorus adsorption capacity of attapulgite.

Adsorption of endocrine disruptive congo red onto biosynthesized silver nanoparticles loaded on Hildegardia barteri activated carbon

In this research work, silver nanoparticles (AgNPs) were prepared using green procedure and loaded on Hildegardia barteri activated carbon (HBAC) and then characterized for determination of morphology, crystals structure, functional groups, surface area and porosity, and size distribution, of the composite material using Scanning electron microscope equipped with energy dispersive X-ray spectroscopy (SEM-EDX), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), Brunauer Emmett Teller (BET), and High-resolution transmission electron microscope (HRTEM). The AgNPs/HBAC nanocomposite was used for the removal of Congo red (CR) dye from aqueous solution. The antimicrobial activity of AgNPs/HBAC was tested against Pseudomonas aeruginosa, Salmonella typhi, Escherichia coli and Bacillus subtilis bacteria using the agar well diffusion method. Parameters such as initial CR concentration (20–100 mg/L), adsorbent dosage (0.1–1 g), contact time (0–90 min), and adsorption temperature (308, 318 and 328 K) were investigated on a batch adsorption process to estimate the CR removal efficiency. The mesoporous AgNPs/HBAC had a BET surface area of 794 m2/g which enhanced CR adsorption capacity (161.29 mg/g). The Freundlich isotherm emerged the best fitted model, indicating surface heterogeneity (multilayer adsorption) between the CR and AgNPs/HBAC surface. The CR adsorption onto AgNPs/HBAC was adequately described by a pseudo-second order kinetic model, and the overall adsorption process was governed by Webber-Morris intraparticle diffusion, and liquid film diffusion models. Thermodynamic study revealed that the adsorption ability of AgNPs/HBAC toward CR was spontaneous, feasible, and exothermic. The developed AgNPs/HBAC could be used as a nano-adsorbent to mitigate the environmental problems caused by CR in wastewater. Regeneration and reusability of AgNPs/HBAC adsorption performance indicated adsorption efficiency greater than 85 % after five successive cycles.

Biosorption investigation of Cu(II) ions from aqueous solutions using sericin–alginate particles: Kinetic, equilibrium, and thermodynamic

In this study, sericin–alginate particles are produced for use as a biosorbent to remove Cu(II) ions from an aqueous solution in a batch biosorption system. Sericin is a protein present in silkworm cocoons and is considered a byproduct of the silk industry. Its use in the production of biosorbents has emerged as an environmentally friendly alternative. Sericin–alginate particles are characterized using N2 physical adsorption analysis, scanning electron microscopy, Fourier transform infrared spectroscopy, and point of zero charge. Additionally, they are evaluated via kinetic, isothermal, and thermodynamic biosorption tests. Kinetic modeling is performed using Lagergren pseudo-first-order, pseudo-second-order, Weber–Morris intraparticle diffusion, homogeneous solid diffusion, and external liquid-film diffusion models. For equilibrium modeling, the Langmuir, Freundlich, and Temkin isotherm models are applied. The Cu(II) ions biosorption is spontaneous and exothermic, as biosorption capacity decreases with temperature: 87.27 mg g-1 (20 °C), 82.54 mg g-1 (40 °C), and 76.18 mg g-1 (60 °C). Based on kinetic modeling, it is verified that internal mass transfer limits the biosorption rate. The Langmuir isotherm model shows a better fit for the biosorption equilibrium, indicating that biosorption occurs in the monolayer. Tests to evaluate the reusability of sericin–alginate particles are performed. It is discovered that even after five adsorption–desorption cycles, the biosorbent shows excellent biosorption capacity. The obtained results and a comparison of the biosorption capacity of different biomaterials demonstrate the high potential of the sericin–alginate particles as a biosorbent for Cu(II) ions.

Adsorption-Desorption Surface Bindings, Kinetics, and Mass Transfer Behavior of Thermally and Chemically Treated Great Millet Husk towards Cr(VI) Removal from Synthetic Wastewater

This study reports the efficacy of adsorbents synthesized by thermal (TT-GMH) and chemical (CT-GMH) modification of great millet husk (GMH) for the treatment of synthetic wastewater containing Cr(VI). The chemical modification of raw GMH was done by concentrated H2SO4 to increase the porosity and heterogeneity on the surface. The comparative investigations of physicochemical properties of synthesized adsorbents were examined by point of zero charge (pHpzc), BET surface area, SEM-EDX, FTIR, and XRD analyses. The results revealed that CT-GMH had around three times higher surface area and more porous structure as compared to TT-GMH. The adsorption experiments were executed in batch mode to examine the impact of parameters governing the adsorption process. For Cr(VI) solution of 25 mg/L, adsorbent dose of 4 g/L, temperature of 25[Formula: see text], and shaking speed of 150 RPM, the maximum removal for TT-GMH was attained at pH 1 and contact time 150 min, while for CT-GMH, maximum removal was attained at pH 2 and contact time 120 min. The experimental results fitted to the rate kinetic equations showed that for both TT-GMH and CT-GMH, adsorbents followed the quasi-second-order kinetic model during the adsorption process. Further, results revealed that the adsorption process was endothermic and Sips isotherm model was followed for both TT-GMH and CT-GMH. Based on the Sips isotherm, maximum uptake capacity for TT-GMH and CT-GMH was noted to be 16 and 22.21 mg/g, respectively. Among the tested mass transfer models, liquid film diffusion model was followed during the adsorption process of both the adsorbents. The desorption study revealed that TT-GMH and CT-GMH give 69.45% and 74.48% removal, respectively, up to six cycles.

Structural Adaptive, Self-Separating Material for Removing Ibuprofen from Waters and Sewage.

β-Cyclodextrin nanosponge (β−CD−M) was used for the adsorption of ibuprofen (IBU) from water and sewage. The obtained material was characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), Brunauer–Emmett–Teller (BET), Barrett–Joyner–Halenda (BJH), Harkins and Jura t-Plot, zeta potential, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and elementary analysis (EA). Batch adsorption experiments were employed to investigate the effects of the adsorbent dose, initial IBU concentration, contact time, electrolyte ions and humic acids, and sewage over adsorption efficiency. The experimental isotherms were show off using Langmuir, Freundlich, Hill, Halsey and Sips isotherm models and thermodynamic analysis. The fits of the results were estimated according to the Sips isotherm, with a maximum adsorption capacity of 86.21 mg g−1. The experimental kinetics were studied by pseudo-first-order, pseudo-second-order, Elovich, modified Freundlich, Weber Morris, Bangham’s pore diffusion, and liquid film diffusion models. The performed experiments revealed that the adsorption process fits perfectly to the pseudo-second-order model. The Elovich and Freundlich models indicate chemisorption, and the kinetic adsorption model itself is complex. The data obtained throughout the study prove that this nanosponge (NS) is extremely stable, self-separating, and adjusting to the guest structure. It also represents a potential biodegradable adsorbent for the removal IBU from wastewaters.

Adsorption Behavior of Hydroquinone by Diatomite-based Porous Ceramsite

Diatomite-based porous ceramsite is a new kind of environmental material. In this study, ceramsite was prepared by wet grinding, a rolling-ball method, and high temperature-calcination using diatomite as the main raw material with the addition of a pore-forming agent and sintering assistant. X-ray diffraction, scanning electron microscopy, and mercury injection, were used to analyze the structure and characteristics of the prepared materials. Using hydroquinone as the target pollutant, the adsorption behavior of diatomite-based porous ceramsite was investigated. Results indicated that the diatomite-based porous ceramsite had a pore size ranging from 500 to 3000 nm, a specific surface area of 6.14 m2.g-1, and a porosity of 47.8%. When pH was 7, the removal rate and adsorption capacity of the hydroquinone by the diatomite-based porous ceramsite was 91.2% and 4.56 m2.g-1, respectively. In the adsorption process of hydroquinone by diatomite-based porous ceramsite, the diffusion of a liquid membrane was dominant, which could be better described by the quasi-first-order kinetic equation. The Langmuir and Koble-Corrigan equations had a higher fitting degree of data for the adsorption isotherms. The adsorption characteristics of the diatomite-based porous ceramsite are in accordance with the fixed-point adsorption of a single molecular layer and belong to a heterogeneous composite adsorption system. The correlation coefficient R2 and k value of hydroquinone adsorption by the diatomite-based porous ceramsite determined by the liquid film diffusion model were 0.848 and 0.0417, respectively.

Removal of methylene blue dye from aqueous solution using citric acid modified apricot stone

In this study, apricot stones were modified with citric acid and used in the adsorption of methylene blue. Fourier transform infrared (FT-IR) Scanning electron microscopy (SEM), and X-Ray Diffraction (XRD) were used to characterize the adsorbent. The influence of the initial pH, temperature, contact time, and initial concentration on the adsorption process was investigated. The thermodynamic investigation showed that adsorption was spontaneous and the adsorption process was endothermic. In experimental studies, isotherm models by Langmuir, Freundlich, Temkin, and Dubinin – Radushkevich (D-R) were analyzed and experimental data showed the best agreement with the Temkin isotherm model. We found that the maximum monolayer adsorption capacity for the Langmuir isotherm model was 19.01 mg/g. Pseudo-first and second-order models were examined and, according to the results of the kinetic model analysis, the highest correlation coefficient (R2> 0.99) belongs to the pseudo-second-order kinetic model. It was concluded that the adsorption mechanism was carried out in both the intra-particle diffusion and the liquid film diffusion model.

Linear and nonlinear investigations for the adsorption of paracetamol and metformin from water on acid-treated clay

Natural clays are considered a safe, low-cost, and sound sorbent for some pharmaceutical and body care products from water. Metformin (MF) and paracetamol (PA) are of the most consumable drugs worldwide. A portion of natural clay was treated with distilled water, and another part was treated with hydrochloric acid. The water-treated clay (WTC) and the acid-treated clay (ATC) were characterized by scanning electron microscopy-energy dispersive spectroscopy, X-ray diffraction, Fourier transforms infrared spectroscopy, and nitrogen adsorption isotherm. Batch experiments were employed to investigate the influence of contact time and solution parameters on the adsorption of PA and MF on WTC and ATC. 30 min attained the equilibrium for all sorbent-sorbate systems. Both sorbents fitted the pseudo-second-order kinetic model with a preference to the nonlinear fitting, and the mechanism of adsorption partially fitted the liquid-film diffusion model. The PA and MF adsorption on WTC and ATC fitted the Freundlich model in preference to nonlinear fitting. The adsorption of pollutants on both sorbents was spontaneous, exothermic, and physisorption in nature. Even at low concentrations, both WTC and ATC showed efficiency above 80% in removing PA and MF from tab water, groundwater, and Red seawater. These findings nominated natural clay as an alternative to the costly nanomaterials as sorbents for removing pharmaceutical contaminants from water.

β-cyclodextrin and magnetic graphene oxide modified porous composite hydrogel as a superabsorbent for adsorption cationic dyes: Adsorption performance, adsorption mechanism and hydrogel column process investigates

The β-cyclodextrin/magnetic graphene oxide (β-CD/MGO) functionalized polyacrylic acid-based porous superabsorbent composite hydrogel adsorbent (β-CD/MGO/PAA) was prepared via simple one-pot polymerization. Fourier transform infrared spectra (FT-IR), Raman spectra (Raman), scanning electron microscopy (SEM), The thermogravimetric analysis (TGA) and vibrating sample magnetometry (VSM) confirmed the successfully synthesized of β-CD/MGO/PAA hydrogel. This hydrogel as-prepared combined the advantages of β-cyclodextrin, magnetic graphene oxide and polyacrylic acid, owned exceedingly plentiful carboxyl and hydroxyl groups, and provide a large number of adsorption active sites. β-CD/MGO/PAA hydrogel adsorption performance test showed excellent removal efficiency for 50 mg/L of methylene blue (MB), safranine T (ST), rhodamine B (RhB) and malachite green (MG), which were 99.1%, 98.5%, 97.1% and 95.0%, respectively. Furthermore, batch and filtration adsorption experiments towards MB and ST were carried out to investigate the adsorption capacity and mechanisms in detail. Pseudo-first-order, Pseudo-second-order, Intra-particle diffusion and Liquid film diffusion models were used to evaluate the adsorption kinetic data while Langmuir isotherm, Freundlich isotherm and Temkin isotherm models were used to evaluate adsorption equilibrium data. The adsorption capacity of MB and ST at 298 K were as high as 2802.67 mg/g and 1470.33 mg/g, respectively. Meanwhile, β-CD/MGO/PAA hydrogel can effective selectively adsorbed cationic dyes in cationic/anionic mixture dyes solution, and can quickly separate from the aqueous solution under the action of an external magnetic field. Moreover, removal efficiency of MB and ST still were reached 95.0% and 85.0% after eight adsorption–desorption cycles. We found that electrostatic interactions, hydrogen bond interactions, π-π conjugate interactions and host–guest supramolecular interactions existed between β-CD/MGO/PAA hydrogel and cation dyes molecules in adsorption process. Finally, it was demonstrated that the β-CD/MGO/PAA hydrogel was suitable for used as adsorption column packing to rapidly purify wastewater by filtration.

Extensive analyses of mass transfer, kinetics, and toxicity for hazardous acid yellow 17 dye removal using activated carbon prepared from waste biomass of Solanum melongena

The present study was focused on the synthesis of brinjal waste activated carbon (BWAC) from the dry woody part of brinjal plant by chemical activation method. The BWAC was used as adsorbent to remove acid yellow 17 (AY-17) from the synthetic solution. For BWAC synthesis, phosphoric acid was used as a chemical reagent for chemical activation at a ratio of 1:1, followed by pyrolysis of chemically treated biomass in N2 atmosphere at high temperatures in a vertical reactor for improved chemical and surface properties of BWAC. The BWAC was characterized by several techniques such as BET surface area, pore distribution, SEM, FTIR, XRD, and point of zero charge (pHPZC). Various affecting parameters such as equilibrium time, initial pH, BWAC dose, AY-17 concentrations, and temperature for dye removal by BWAC were also investigated in the batch experiment. The maximum of 99.58% removal of AY-17 dye by BWAC occurred at pH 3. More than 97% dye was removed by BWAC from aqueous solution for initial 15 mg/L AY-17 dye concentration with other conditions such as 2 g/L dose, 5.00 ± 0.2 pH, 80 min equilibrium time, and 25 °C temperature. Therefore, further experiments were carried out at pH 5. Equilibrium data were fitted with the isotherm models such as Langmuir, Freundlich, and Temkin, and according to the correlation coefficient (R2), the Langmuir model was best fitted among them. The experimental kinetic data was well-validated with the pseudo-second-order kinetic model. The mass transfer studies of the dye onto BWAC were described by three models, such as Weber-Morris (intra-particle diffusion), Banghum’s, and liquid film diffusion models, and the result reported that all steps were involved for the adsorption process. The order for the rate-determining step, according to R2, was intra-particle diffusion > Bangham’s model > liquid film diffusion model. Recovery and recycling of dye-treated BWAC with desorption efficiency of ~ 73% was possible by 1 M NaOH treatment after 5th cycles. The simulated dye solution after treatment by BWAC was used in seed germination for toxicity assessment.

Efficient synthesis of magnetic nanoparticle-Musa acuminata peel composite for the adsorption of anionic dye

The impregnation of magnetite (Mt) nanoparticle (NPs) onto Musa acuminata peel (MApe), to form a novel magnetic combo (MApe-Mt) for the adsorption of anionic bromophenol blue (BPB) was studied. The SEM, EDX, BET, XRD, FTIR and TGA were used to characterize the adsorbents. The FTIR showed that the OH and CO groups were the major sites for BPB uptake onto the adsorbent materials. The average Mt crystalline size on MApe-Mt was 21.13 nm. SEM analysis revealed that Mt NPs were agglomerated on the surface of the MApe biosorbent, with an average Mt diameter of 25.97 nm. After Mt impregnation, a decrease in BET surface area (14.89 to 3.80 m2/g) and an increase in pore diameter (2.25–3.11 nm), pore volume (0.0052–0.01418 cm3/g) and pH point of zero charge (6.4–7.2) was obtained. The presence of Pb(II) ions in solution significantly decreased the uptake of BPB onto both MApe (66.1–43.8%) and MApe-Mt (80.3–59.1%), compared to other competing ions (Zn(II), Cd(II), Ni(II)) in the solution. Isotherm modeling showed that the Freundlich model best fitted the adsorption data (R2 > 0.994 and SSE < 0.0013). In addition, maximum monolayer uptake was enhanced from 6.04 to 8.12 mg/g after Mt impregnation. Kinetics were well described by the pseudo-first order and liquid film diffusion models. Thermodynamics revealed a physical, endothermic adsorption of BPB onto the adsorbents, with ΔHo values of 15.87–16.49 kJ/mol, corroborated by high desorption (over 90%) of BPB from the loaded materials. The viability of the prepared adsorbents was also revealed in its reusability for BPB uptake.