The Elovich isotherm equation: Back to the roots and new developments

Optimizing acid microemulsions for cleaner gas production: A study on enhanced adsorption characteristics and implications in retardation

The ultralow interfacial tension between the oil and aqueous phases and the solubilization characteristics in microemulsion systems make them useful for surface cleaning and enhanced oil recovery applications. Microemulsions can form an adsorbed barrier on rock, reducing the acid-rock reaction rate. However, as acid retardation additives, the adsorption patterns of microemulsions are not clearly defined. In this study, microemulsions composed of various electrical surfactants, oil cores, and oil core additives were obtained, and their phase behaviors were investigated. Through adsorption and reaction experiments, cleaning microemulsions that enhance adsorption effects were identified, and their adsorption patterns and adaptability under flow conditions were evaluated. The results demonstrate that incorporating negatively charged polar compounds forms an enhanced adsorption microemulsion characterized by an average droplet size of less than 30 nm after mixing with the acid. The introduction of negatively charged polar compounds resulted in a 177 % increase in adsorption and an 81 % improvement in static retardation effect. Dynamic adsorption tests indicate that the pseudo-second-order model more accurately describes the kinetics of dynamic adsorption of microemulsions on rock surfaces. Under a fixed flow rate, the dynamic retardation rate increased with the concentration of the microemulsion. In practical acidification, the adsorption of microemulsions results mainly from combined electrostatic forces and fluid scouring, characterized by a continuous process of adsorption and desorption. Scanning electron microscope also confirmed that microemulsions can form an adsorptive film on the rock, reducing the acid-rock reaction rate. This study offers practical guidelines for the selection and application of retardation additives, aiming to enhance the ecological compatibility of chemical treatments in low-permeability limestone reservoirs.

Removal of Azo Dyes from Water Using Natural Luffa cylindrica as a Non-Conventional Adsorbent

Reducing high concentrations of pollutants such as heavy metals, pesticides, drugs, and dyes from water is an emerging necessity. We evaluated the use of Luffa cylindrica (Lc) as a natural non-conventional adsorbent to remove azo dye mixture (ADM) from water. The capacity of Lc at three different doses (2.5, 5.0, and 10.0 g/L) was evaluated using three concentrations of azo dyes (0.125, 0.250, and 0.500 g/L). The removal percent (R%), maximum adsorption capacity (Qm), isotherm and kinetics adsorption models, and pH influence were evaluated, and Fourier-transform infrared spectroscopy and scanning electron microscopy were performed. The maximum R% was 70.8% for 10.0 g L-1Lc and 0.125 g L-1 ADM. The Qm of Lc was 161.29 mg g-1. Adsorption by Lc obeys a Langmuir isotherm and occurs through the pseudo-second-order kinetic model. Statistical analysis showed that the adsorbent dose, the azo dye concentration, and contact time significantly influenced R% and the adsorption capacity. These findings indicate that Lc could be used as a natural non-conventional adsorbent to reduce ADM in water, and it has a potential application in the pretreatment of wastewaters.

Sulfuric acid-assisted ball milling for the preparation of Si-O-enriched straw biochar: removal efficiency of rhodamine B and adsorption mechanism

Traditional pyrolysis biochar has been widely employed to treat dye wastewater. However, there are some problems in the pyrolysis process, such as the generation of harmful gases and the low content of silico-oxygen functional groups to promote adsorption. Straw biochar (Ac-BCbm) was prepared by sulfuric acid co-ball milling method. The adsorption performance and adsorption mechanism of rhodamine B (RhB) under different preparation conditions and factors were investigated. The results showed that the adsorption rate of Ac-BCbm on RhB was up to 94.9%, which was 60.5% and 55.8% higher than that of ball-milling straw (STbm) and biochar prepared by pyrolysis (STBC600), respectively. The Ac-BCbm had better adaptability under different pH and common interfering ions for remove RhB. Characterization and DFT simulation analysis revealed that the sulfuric acid co-ball milling process promoted the formation of Si-OH and Si-O-CH3 oxygen-containing functional groups of Si component in straw, which enhanced the hydrogen bonding interactions and effectively improved the adsorption efficiency. This study investigated a new strategy for biochar preparation by sulfuric acid co-ball milling, which provides an additional development direction for the efficient resource utilization of straw.

Development of p-n Heterostructures Using Phosphorene and SnO2: Its Efficacy toward the Adsorption Study of CO2 and Rose Bengal Dye

Adsorption-mediated methods for environmental pollution control are suitable as they are cost-effective and easy to use. Porous materials can play an important role in adsorption studies. Herein, we synthesized a p-n heterostructure of phosphorene and metal oxide using a simple hydrothermal approach. The synthesized material is porous in nature, with a surface area of 127.44 m2/g and pore volume of about 1.73 nm with appreciable thermal stability. As the material is microporous, we used it for the adsorption of CO2 gas and dye. For CO2 adsorption, we determined the CO2 gas uptake according to the mass balance principle of the ideal gas equation, and it was found to be about 21.478 mol/kg. We have also studied different isotherm models to check the adsorption phenomena. Moreover, for dye adsorption, we have chosen the xanthene-derived rose bengal (RB) dye, which shows a removal percentage of about 92.02%. In the case of dye adsorption, the material shows good reusability and significant adsorption up to five cycles.

Surface activity, mechanisms, kinetics, and thermodynamic study of adsorption of malachite green dye onto sulfuric acid-functionalized Moringa oleifera leaves from aqueous solution

In the present study, activated carbon prepared from H2SO4-functionalized Moringa oleifera leaves (ACMOL) was used as a potential adsorbent for the effective removal of malachite green (MG) dye from aqueous media. FT-IR, SEM, EDS, Zeta potential, XRD, BET, proximate, and CHNS analysis techniques were used for surface characterization of the ACMOL. The adsorption efficiency of the ACMOL was investigated as a function of varying adsorbent dosage (0.02-0.2 g/100 mL), pH (3.0-9.0), ionic strength (0.1-0.5 M KCl), urea concentration (0.1-0.5 M), contact time (30-210 min), and temperature (303-323 K). The representative adsorption isotherms belong to the typical L-type. Maximum percentage removal was found to be 84% (124.40 mg/g) for MG dye concentration (30 mg/L) at pH 7.0 and 303 K with ACMOL dose 0.02 g/100 mL. The adsorption kinetics and equilibrium experimental data of MG dye adsorption on the ACMOL were well explained by the pseudo-second-order kinetics (R2 = 0.99) and Langmuir isotherm model (R2 = 0.99), respectively. The value of adsorption and desorption coefficient was found to be 0.036 min-1 and 0.025 mg min-1/L, respectively. Thermodynamic study showed the spontaneous (ΔG° =  - 31.33, - 31.92, and - 32.49 kJ/mol at temperatures 303 K, 313 K, and 323 K, respectively) and exothermic (ΔH° =  - 13.7 kJ/mol) nature of the adsorption with some structural changes occurring on the ACMOL surface (ΔS° = 58.198 J/K·mol).

Surface activity, kinetics, thermodynamics and comparative study of adsorption of selected cationic and anionic dyes onto H3PO4-functionalized bagasse from aqueous stream

The discharge of dyes into the water body creates toxicity to aquatic organisms because of their aromatic structure and difficult degradation. So, the treatment of dye-contaminated wastewater is required before releasing it. In the present study, thermally treated (600 °C) and H3PO4 (55%)-functionalized bagasse, henceforth called thermochemically activated bagasse (TCAB), was synthesized as potential adsorbent for the effective removal of selected cationic and anionic dyes from their aqueous stream. TCAB characterization was done employing FT-IR, SEM, XRD, zeta potential, BET, and PZC techniques. The comparative study shows that the relative adsorption on TCAB followed the sequence, methyl red (185 mg/g) > safranin (178 mg/g) > congo red (146 mg/g) > brilliant green (139 mg/g) > malachite green (130 mg/g) > bromocresol green (94 mg/g). The adsorption efficiency was investigated concerning the effect of change in TCAB dose (0.05-0.3 g/100 mL), initial dye concentration (20-200 mg/L), pH (4.0-10.0), ionic strength (0.1-0.5 M KCl), urea concentration (0.1-0.5 M) and temperature (25-45 °C). The representative adsorption isotherms belong to typical L-type. The time-dependent dye removal was best explained by the pseudo-second-order (PSO) kinetic model (R2 = 0.9859-0.9991), while equilibrium data were best explained by the Freundlich model (R2 = 0.9881-0.9961). Thermodynamic study showed the spontaneous (ΔG0 <0) and exothermic nature (ΔH0 <0) of the adsorption of different cationic and anionic dyes. The cyclic adsorption ability of TCAB for different dyes was checked up to three cycles (185 to 168 mg/L for MR, 178 to 165 mg/L for SF, 146 to 130 mg/L for CR, 139 to 127 mg/L for BG, 130 to 114 mg/L for MG and 94 to 80 mg/L for BCG), and no significant decrease in the adsorption capacity was noticed. So, the present study provides valuable insights into the adsorption of cationic and anionic dyes onto H3PO4-functionalized bagasse. Addressing the adsorptive aspects enhances the clarity, reliability and applicability of the study's findings and contributes to its overall scientific impact.

Magnetic Core@Shell Fe3O4@Polypyrrole@Sodium Dodecyl Sulfate Composite for Enhanced Selective Removal of Dyestuffs and Heavy Metal Ions from Complex Wastewater

Adsorption materials have demonstrated huge potential in treating sewage; however, it is a great challenge to fabricate an adsorbent effectively adsorbing multiple dyestuffs and heavy metal ions simultaneously. Here, a magnetic core@shell Fe3O4@polypyrrole@sodium dodecyl sulfate (Fe3O4@PPy@SDS) composite is prepared through the combination of a hydrothermal method, an in situ polymerization method, and modification, exhibiting enhanced selective removal of five dyestuffs (methylene blue (MB), malachite green (MG), rhodamine B (RhB), Congo red (CR), acid red 1 (AR1)), and heavy metal ions (Mn(VII)). The effects of adsorbent type, time, initial concentration of the adsorbate, and temperature on adsorption performances are investigated in detail. Kinetics and isotherm studies indicate that all adsorption processes are more in line with the pseudo-second-order kinetic model and the Langmuir model, the diffusion behavior is controlled by intraparticle diffusion and liquid film diffusion, and research of thermodynamics reveals a spontaneous endothermic behavior. The removal efficiency after five desorption-adsorption cycles can still reach more than 90%. The prepared Fe3O4@PPy@SDS composite is an efficient and promising renewable adsorbent for the treatment of dyestuffs and Mn(VII), exhibiting a wide range of applications in the field of adsorption.