Facile preparation of sisal-Fe/Zn layered double hydroxide bio-nanocomposites for the efficient removal of rifampin from aqueous solution: kinetic, equilibrium, and thermodynamic studies

Immobilization of polypyrrole on waste face masks using a novel in-situ-surface polymerization method: removal of Cr(VI) from electroplating wastewater

In this work, polypyrrole (PPy) was synthesized on the surface of waste surgical face masks (SFM) with a novel environmentally-friendly in-situ-surface polymerization approach and used as an adsorbent for removing hexavalent chromium (Cr(VI)). In this method, the SFM surface was activated using KMnO4, resulting in the immobilization of porous MnO2, on which pyrrole can be polymerized efficiently. The novelty of this method is the presence of the oxidant on the surface before the polymerization step, which results in a better surface modification with polypyrrole. This method provides adsorbents with higher adsorption capacity compared to the conventional polymerization method with ammonium persulfate (APS). The adsorbent prepared at the mass ratios of 1.0 and 2.0; respectively, for KMnO4/SFM and pyrrole/SFM showed the highest performance. The adsorbent characterization revealed the successful polymerization of pyrrole on the surface of SFM. Reusability of the KMnO4 and pyrrole solutions were successful with remarkable results, showing the advantage of this technique compared to the conventional polymerization method with APS. The effect of different factors on the adsorption process was investigated. The removal rate was around 98% under the optimum conditions (pH, 2; adsorbent dosage, 3 g L-1; contact time, 60 min). The equilibrium data were well fitted by Langmuir isotherm (R2 =  0.9999). Kinetic investigations revealed that the adsorption process fitted well with the pseudo-second-order model. The adsorbent was regenerated for up to five cycles. One of the most important advantages of the proposed method compared to other methods is the reduction of wastewater during the synthesis process.

Optimization and characterization of silver nanoparticle-modified luffa for the adsorption of ketoprofen and reactive yellow 15 from aqueous solutions

In the current work, luffa was modified with silver nanoparticles to prepare LF/AgNPs adsorbent for the elimination of ketoprofen and reactive yellow 15 (RY15) from aqueous media. Various characterization techniques, including FT-IR, XRD, BET, and SEM-EDS analysis, were employed to confirm the successful modification of LF/AgNPs. Several key parameters such as contact time, adsorbent dosage, concentration, pH, and agitation technique were fine-tuned to optimize the adsorption process. Ketoprofen removal was found to be most effective in weakly acidic conditions (pH = 5), while reactive yellow 15 adsorption was enhanced in an acidic environment (pH = 2). At 298 K, the highest adsorption capacities reached 56.88 mg/g for ketoprofen and 97.76 mg/g for reactive yellow 15. In both scenarios involving the elimination of ketoprofen and RY15, the Temkin isotherm exhibits higher R2 values, specifically 0.997 for ketoprofen and 0.963 for RY15, demonstrating a strong correlation with the observed adsorption data. Additionally, the kinetics of ketoprofen adsorption were best described by the Pseudo-first order model (R2 = 0.989), whereas the Pseudo-second order model provided the most accurate fit for reactive yellow 15 adsorption (R2 = 0.997). Importantly, the LF/AgNPs adsorbent displayed consistent performance over five consecutive reuse cycles, affirming its stability and efficacy in removing both contaminants. These findings underscore the exceptional potential of LF/AgNPs as a reliable adsorbent for the removal of reactive yellow 15 and ketoprofen from aqueous solutions.

Carbon-Supported Nanocomposite Synthesis, Characterization, and Application as an Efficient Adsorbent for Ciprofloxacin and Amoxicillin

The existence of antibiotics in the environment has recently raised serious concerns about their possible hazards to human health and the water ecosystem. In the current study, an activated carbon-supported nanocomposite, AC-CoFe2O3, was synthesized by a coprecipitation method, characterized, and then applied to adsorb different drugs from water. The synthesized composites were characterized by using energy-dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, Brunauer-Emmett-Teller plots, and scanning electron microscopy. The adsorption of both Ciprofloxacin (Cipro) and Amoxicillin (Amoxi) antibiotics on the composite followed the pseudo-second-order kinetic model (R2 = 0.9981 and 0.9974 mg g-1 min-1, respectively). Langmuir isotherm was the best-fit model showing 312.17 and 217.76 mg g-1 adsorption capacities for Ciprofloxacin and Amoxicillin, respectively, at 333 K. The negative Gibbs free energy (ΔG°) specified the spontaneity of the method. The positive change in the enthalpy (ΔH) indicated that the adsorption process was assisted by higher temperatures. The different optimized parameters were pH, contact time, adsorbent weight, concentration, and temperature. The maximum adsorption of Cipro was found to be 98.41% at pH 12, while for Amoxi, it was 89.09% at pH 2 at 333 K. The drugs were then successfully determined from natural water samples at optimized conditions using these nanocomposites.

Deep eutectic solvent-treated palm oil mill sludge adsorbents for methylene blue adsorption

This study evaluated the adsorptive properties of deep eutectic solvent (DES)-treated palm oil mill sludge adsorbents for methylene blue removal. The adsorbents were prepared at a ratio of 1:2 at 80°C to form P1:D2@80°C, at 25°C to form P1:D2@25°C and without DES to form dry sludge (DS). The adsorbent samples were characterized for surface functional groups, textural properties and surface morphology. The values of specific area were 534, 236 and 184 m2/g, respectively. Batch adsorption of methylene blue at varying concentration, adsorbent dosage, pH, contact time and temperature was performed. The maximum adsorption capacities by Sips model were recorded as 72.07, 56.18 and 48.33 mg/g for P1:D2@80°C, P1:D2@25°C and DS, respectively. P1:D2@80°C displayed the highest rate constant (Ks = 0.0037 g/mg.min). The adsorption data were well fitted into Sips isotherm and pseudo-second-order kinetic models, suggesting that the adsorption is a physical process onto heterogeneous adsorbent surface via pore filling and electrostatic attraction. The adsorption was spontaneous, feasible and exothermic with decreased disorderliness in the solid-bulk solution interface. The DES-treated palm oil mill sludge adsorbent is a promising alternative adsorbent for dye removal from wastewater.

Enhanced adsorptive removal of rifampicin and tigecycline from single system using nano-ceria decorated biochar of mango seed kernel

Pharmaceutically active compounds (PhACs) represent an emerging class of contaminants. With a potential to negatively impact human health and the ecosystem, existence of pharmaceuticals in the aquatic systems is becoming a worrying concern. Antibiotics is a major class of PhACs and their existence in wastewater signifies a health risk on the long run. With the purpose of competently removing antibiotics from wastewater, cost-effective, and copiously available waste-derived adsorbents were structured. In this study, mango seeds kernel (MSK), both as a pristine biochar (Py-MSK) and as a nano-ceria-laden (Ce-Py-MSK) were applied for the remediation of rifampicin (RIFM) and tigecycline (TIGC). To save time and resources, adsorption experiments were managed using a multivariate-based scheme executing the fractional factorial design (FrFD). Percentage removal (%R) of both antibiotics was exploited in terms of four variables: pH, adsorbent dosage, initial drug concentration, and contact time. Preliminary experiments showed that Ce-Py-MSK has higher adsorption efficiency for both RIFM and TIGC compared to Py-MSK. The %R was 92.36% for RIFM compared to 90.13% for TIGC. With the purpose of comprehending the adsorption process, structural elucidation of both sorbents was performed using FT-IR, SEM, TEM, EDX, and XRD analyses which confirmed the decoration of the adsorbent surface with the nano-ceria. BET analysis revealed that Ce-Py-MSK has a higher surface area (33.83 m²/g) contrasted to the Py-MSK (24.72 m²/g). Isotherm parameters revealed that Freundlich model best fit Ce-Py-MSK-drug interactions. A maximum adsorption capacity (q_m) of 102.25 and 49.28 mg/g was attained for RIFM and TIGC, respectively. Adsorption kinetics for both drugs conformed well with both pseudo-second order (PSO) and Elovich models. This study, therefore, has established the suitability of Ce-Py-MSK as a green, sustainable, cost-effective, selective, and efficient adsorbent for the treatment of pharmaceutical wastewater.

Effective adsorption of diclofenac sodium from aqueous solution using cationic surfactant modified Cuminum cyminum agri-waste: kinetic, equilibrium, and thermodynamic studies

The occurrence of pharmaceutical pollutants in aqueous media has increased where significant research is being conducted to eliminate these toxic compounds. In the present study, Tetradecyltrimethylammonium bromide (TTAB) modified Cuminum cyminum agri-waste (CCW) was prepared to investigate the removal of diclofenac sodium (DCF) from aqueous solution in the batch process for the first time. Physical and chemical characterizations of as-prepared adsorbent were conducted using field emission scanning electron microscopy, Fourier-transform infrared spectroscopy, N₂ adsorption-desorption, and point of zero charge analysis. Besides, the effect of the main parameters that affect the adsorption process, i.e., adsorbent dosage (0.25-6 g/L), contact time (0-300 min), initial DCF concentration (10-500 mg/L), and pH of the solution, were investigated. Furthermore, the resulted data were analyzed using various kinetic and isotherm models. The Pseudo-second-order model with R² = 0.9981 showed the highest agreement with kinetic behavior. Also, the maximum adsorption capacity of DCF is 93.65 mg/g, according to the Langmuir isotherm. In acidic media, the adsorption capacity reached the highest value (44.69 mg/g). As a result, this study revealed that the agri-waste material could be modified and, as a low-cost adsorbent, have promising adsorption potential to remove pharmaceutical contaminants from the aqueous solution.

Low-cost treated lignocellulosic biomass waste supported with FeCl3/Zn(NO3)2 for water decolorization

Dye pollution has always been a serious concern globally, threatening the lives of humans and the ecosystem. In the current study, treated lignocellulosic biomass waste supported with FeCl₃/Zn(NO₃)₂ was utilized as an effective composite for removing Reactive Orange 16 (RO16). SEM/EDAX, FTIR, and XRD analyses exhibited that the prepared material was successfully synthesized. The removal efficiency of 99.1% was found at an equilibrium time of 110 min and dye concentration of 5 mg L^-1 Adsorbent mass of 30 mg resulted in the maximum dye elimination, and the efficiency of the process decreased by increasing the temperature from 25 to 40 °C. The effect of pH revealed that optimum pH was occurred at acidic media, having the maximum dye removal of greater than 90%. The kinetic and isotherm models revealed that RO16 elimination followed pseudo-second-order (R² = 0.9982) and Freundlich (R² = 0.9758) assumptions. Surprisingly, the performance of modified sawdust was 15.5 times better than the raw sawdust for the dye removal. In conclusion, lignocellulosic sawdust-Fe/Zn composite is promising for dye removal.

Adsorption behavior of rhamnolipid modified magnetic Co/Al layered double hydroxide for the removal of cationic and anionic dyes

In the present research, magnetic rhamnolipid-Co/Al layered double hydroxide (MR-LDH) was synthesized to uptake methylene blue (MB) and reactive orange 16 (RO16) from aqueous solution. The main parameters, including pH, adsorbent dosage, contact time, and initial analyte concentration, were optimized to achieve the best adsorption efficiency. Accordingly, the elimination of MB on MR-LDH is improved in the basic medium due to the electrostatic interactions between the negative charge of MR-LDH and the positive charge of MB dye. In contrast, the acidic medium (pH = 3) was favored for RO16 adsorption because of hydrogen bonding between the protonated form of azo dye and protonated hydroxyl groups at the surface of MR-LDH. The calculated maximum adsorption capacities for MB and RO16 were 54.01 and 53.04 mg/g at 313 K, respectively. The Langmuir model, which assumes monolayer adsorption on the adsorbent surface, provides the best explanation for the adsorption of both dyes (R² = 0.9991 for MB and R² = 0.9969 for RO16). Moreover, the pseudo-second-order kinetic model best described the adsorption process for MB (R² = 0.9970) and RO16 (R² = 0.9941). The proposed adsorbent maintains stable adsorption performance for four consecutive cycles. After each adsorption process, MR-LDH is easily separated by an external magnet. The findings show that MR-LDH was found to be an excellent adsorbent for the removal of both cationic and anionic organic dyes from aqueous solutions.