Green synthesis of zinc oxide nanoparticles loaded on activated carbon prepared from walnut peel extract for the removal of Eosin Y and Erythrosine B dyes from aqueous solution: experimental approaches, kinetics models, and thermodynamic studies

Azadirachta indica leaf extract based green-synthesized ZnO nanoparticles coated on spent tea waste activated carbon for pharmaceuticals and personal care products removal

Pharmaceuticals and personal care products (PPCPs) are emerging contaminants in aqueous systems, posing threat to both human health and environment. In prior research, predominant focus has been on examining various adsorbents for removing PPCPs from single-pollutant systems. However, no study has delved into simultaneous adsorption of PPCPs multi-pollutant mixture. This study evaluates performance of Azadirachta indica leaf extract-based green-synthesized ZnO nanoparticles coated on spent tea waste activated carbon (ZTAC) for removing sulfadiazine (SZN) and acetaminophen (ACN). Adsorption investigations were conducted in single-component (ACN/SZN) and binary-component (ACN + SZN) systems. The synthesized ZTAC was characterized using SEM, XRD, FTIR, EDX, porosimetry and pHpzc analysis. The study examines impact of time (1-60 min), dose (0.2-4 g/L), pH (2-12) and PPCPs concentration (1-100 mg/L) on ACN and SZN removal. Various kinetic and isotherm models were employed to elucidate mechanisms involved in sorption of PPCPs. Furthermore, synergistic and antagonistic aspects of sorption process in multi-component system were investigated. ZTAC, characterized by its crystalline nature and surface area of 980.85 m2/g, exhibited maximum adsorption capacity of 47.39 mg/g for ACN and 34.01 mg/g for SZN under optimal conditions of 15 min, 3 g/L and pH 7. Langmuir isotherm and pseudo-second-order kinetic model best-fitted the experimental data indicating chemisorption mechanism. Removal of ACN and SZN on ZTAC demonstrated synergistic nature, signifying cooperative adsorption. Overall, valorization of ZTAC offers effective and efficient adsorbent for elimination of PPCPs from wastewater.

Activated carbon and their nanocomposites derived from vegetable and fruit residues for water treatment

Water pollution remains a pressing environmental issue, with diverse pollutants such as heavy metals, pharmaceuticals, dyes, and aromatic hydrocarbon compounds posing a significant threat to clean water access. Historically, biomass-derived activated carbons (ACs) have served as effective adsorbents for water treatment, owing to their inherent porosity and expansive surface area. Nanocomposites have emerged as a means to enhance the absorption properties of ACs, surpassing conventional AC performance. Biomass-based activated carbon nanocomposites (ACNCs) hold promise due to their high surface area and cost-effectiveness. This review explores recent advancements in biomass-based ACNCs, emphasizing their remarkable adsorption efficiencies and paving the way for future research in developing efficient and affordable ACNCs. Leveraging real-time communication for ACNC applications presents a viable approach to addressing cost concerns.

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.

Synthesis and characterization of iron oxide-commercial activated carbon nanocomposite for removal of hexavalent chromium (Cr6+) ions and Mordant Violet 40 (MV40) dye

Iron Oxide-commercial activated carbon nanocomposite (CAC-IO) was prepared from commercial activated carbon (CAC) by the co-precipitation method, and the resulting nanocomposite was used as an adsorbent to remove hexavalent chromium (Cr6+) ions and Mordant Violet 40 (MV40) dye from wastewater. The produced materials (CAC, CAC after oxidation, and CAC-IO) were comparatively characterized using FTIR, BET, SEM, EDX TEM, VSM, and XRD techniques. The adsorption mechanism of Cr6+ ions and MV40 dye on CAC-IO was examined using Langmuir and Freundlich isotherm models.. Different models were applied to know the adsorption mechanism and it was obtained that Pseudo-second order fits the experimental data better. This means that the adsorption of the adsorbate on the nanocomposite was chemisorption. The maximum removal percent of Cr6+ ions by CAC-IO nanocomposite was 98.6% determined as 2 g L-1 adsorbent concentration, 100 mg L-1 initial pollutant concentration, solution pH = 1.6, the contact time was 3 h and the temperature was room temperature. The maximum removal percentage of Mordant Violet 40 dye (C.I. 14,745) from its solutions by CAC-IO nanocomposite was 99.92% in 100 mg L-1 of initial dye concentrations, 1.0 g L-1 of adsorbent concentration, solution pH = 2.07, the contact time was 3 h. The MV40 dye adsorption on CAC-IO was the most fitted to the Freundlich isotherm model. The maximum adsorption capacity was calculated according to the Langmuir model as 833.3 mg g-1 at 2 g L-1 of adsorbent concentration and 400 mg L-1 of initial MV40 dye concentration. The Cr6+ ions adsorption on CAC-IO was more fitted to the Freundlich model with Qmax, equal to 312.50 mg g-1 at 1 g L-1 adsorbent concentration and 400 mg L-1 of Cr6+ ions initial concentrations.

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).

Lanthanum nanoparticle (La2O3)-loaded adsorbents for removal of hexavalent chromium: a kinetics, isotherm, and thermodynamic study

Nanocomposite adsorbents for wastewater treatment gained popularity in recent times. In the present study, nanoparticles prepared from lanthanum have been loaded on the powdered form of aquatic plants Salvinia molesta (S. molesta) and Typha latifolia (T. latifolia). These new adsorbents were NPS (nanoparticle-loaded S. molesta) and NPT (nanoparticle-loaded T. latifolia). The batch study was carried out to assess the effect of several factors on the adsorption of Cr(VI) by novel adsorbents NPS and NPT. XRD, SEM, FTIR, EDX, and Zeta potential were used for the characterization of nanoparticles formed and novel adsorbents. The maximal adsorption was noticed by both adsorbents at pH 1, 20 ppm of initial metal concentration, and 1 h of contact period with 150 rpm at 25 ℃. The adsorbent dose of 60 mg and 80 mg was observed as the equilibrium dose for NPS and NPT, respectively. The maximum adsorption capacity observed was 27.18 mg/g for NPS and 19.85 mg/g for NPT. Freundlich isotherm was better fitted for both adsorbents. Pseudo-second-order kinetics depicts the better mechanism of adsorption with R2 = 0.9995 and 0.9982 for NPS and NPT, respectively. Thermodynamic parameters show that the adsorption process was exothermic and spontaneous.

Adsorption and separation of Cs(I) and Ba(II) from aqueous solution using zinc ferrite-humic acid nanocomposite

Reclaimable adsorbents have an essential role in removing radionuclides from waste streams. Herein, zinc ferrite-humic acid ZFO/HA nanocomposite was synthesized for effective cesium and barium adsorption. The prepared ZFO/HA nanocomposite was analyzed using analytical techniques including XRD, FTIR, EDX, and SEM. From kinetic studies, the mechanism adsorption process follows the second model. The isotherm studies clarified that the Langmuir model fit the adsorption of both ions onto the prepared sample, and the monolayer capacities are equal to 63.33 mg/g and 42.55 mg/g for Ba(II) and Cs(I), respectively. The temperature parameter was also studied, and the adsorption reaction was spontaneous and endothermic. The maximum separation between two ions was achieved at pH 5 (αCs/Ba = 3.3).

Anaerobic Membrane Bioreactor (AnMBR) for the Removal of Dyes from Water and Wastewater: Progress, Challenges, and Future Perspectives

The presence of dyes in aquatic environments can have harmful effects on aquatic life, including inhibiting photosynthesis, decreasing dissolved oxygen levels, and altering the behavior and reproductive patterns of aquatic organisms. In the initial phase of this review study, our aim was to examine the categories and properties of dyes as well as the impact of their toxicity on aquatic environments. Azo, phthalocyanine, and xanthene are among the most frequently utilized dyes, almost 70–80% of used dyes, in industrial processes and have been identified as some of the most commonly occurring dyes in water bodies. Apart from that, the toxicity effects of dyes on aquatic ecosystems were discussed. Toxicity testing relies heavily on two key measures: the LC50 (half-lethal concentration) and EC50 (half-maximal effective concentration). In a recent study, microalgae exposed to Congo Red displayed a minimum EC50 of 4.8 mg/L, while fish exposed to Disperse Yellow 7 exhibited a minimum LC50 of 0.01 mg/L. Anaerobic membrane bioreactors (AnMBRs) are a promising method for removing dyes from water bodies. In the second stage of the study, the effectiveness of different AnMBRs in removing dyes was evaluated. Hybrid AnMBRs and AnMBRs with innovative designs have shown the capacity to eliminate dyes completely, reaching up to 100%. Proteobacteria, Firmicutes, and Bacteroidetes were found to be the dominant bacterial phyla in AnMBRs applied for dye treatment. However, fouling has been identified as a significant drawback of AnMBRs, and innovative designs and techniques are required to address this issue in the future.

Powdered and beaded sawdust materials modified iron (III) oxide-hydroxide for adsorption of lead (II) ion and reactive blue 4 dye

The problems of lead and reactive blue 4 (RB4) dye contamination in wastewater are concerns because of their toxicities to aquatic life and water quality, so lead and RB4 dye removals are recommended to remove from wastewater before discharging. Sawdust powder (SP), sawdust powder doped iron (III) oxide-hydroxide (SPF), sawdust beads (SPB), and sawdust powder doped iron (III) oxide-hydroxide beads (SPFB) were synthesized and characterized with various techniques, and their lead or RB4 dye removal efficiencies were investigated by batch experiments, adsorption isotherms, kinetics, and desorption experiments. SPFB demonstrated higher specific surface area (11.020 m² g^-1) and smaller pore size (3.937 nm) than other materials. SP and SPF were irregular shapes with heterogeneous structures whereas SPB and SPFB had spherical shapes with coarse surfaces. Calcium (Ca) and oxygen (O) were found in all materials whereas iron (Fe) was only found in SPF and SPFB. O-H, C-H, C=C, and C-O were detected in all materials. Their lead removal efficiencies of all materials were higher than 82%, and RB4 dye removal efficiencies of SPB and SPFB were higher than 87%. Therefore, adding iron (III) oxide-hydroxide and changing material form helped to improve material efficiencies for lead or RB4 dye adsorption. SP and SPB corresponded to Langmuir model related to a physical adsorption process whereas SPF and SPFB corresponded to the Freundlich model correlated to a chemisorption process. All materials corresponded to a pseudo-second-order kinetic model relating to the chemical adsorption process. All materials could be reused more than 5 cycles with high lead removal of 63%, and SPB and SPFB also could be reused more than 5 cycles for high RB4 dye removal of 72%. Therefore, SPFB was a potential material to apply for lead or RB4 dye removal in industrial applications.

Adsorptive removal of pharmaceutically active compounds from multicomponent system using Azadirachta indica induced zinc oxide nanoparticles: analysis of competitive and cooperative adsorption

In this research, zinc oxide (ZnO) nanoparticles synthesized using neem leaf (Azadirachta indica) extract were used as an adsorbent for removing two widely used pharmaceutical compounds acetaminophen (AMP) and sulfadiazine (SDZ). The synthesized ZnO nanoparticles were characterized using SEM-EDS, FTIR, TEM, BET, and XRD analysis. The synthesized ZnO nanoparticles were found to be in the size range of 10 nm with a surface area of 48.551 m²/g. The adsorptive performance of ZnO nanoparticles in both mono-component (MoS) and multi-component system (MuS) was investigated under various operational parameters viz. contact time, temperature, pH, concentration of pharmaceutical compound and ZnO nanoparticles dose. It was observed that the maximum adsorption capacity of ZnO nanoparticles was 7.87 mg/g and 7.77 mg/g for AMP and SDZ, respectively, under the optimum conditions of 7 pH and 2 g/L adsorbent dosage. The experimental data best-fitted with the pseudo-second-order model and Langmuir model, indicating monolayer chemisorption. Further investigation on removal of AMP and SDZ from multicomponent system was modelled using a Langmuir competitive model. The desorption study has shown 25.28% and 22.4% removal of AMP and SDZ from the surface of ZnO nanoparticles. In general, green synthesized ZnO nanoparticles can be utilized effectively as adsorbent for removal of pharmaceutically active compounds from wastewater.