Toma Galaon

This work presents an integrated green chemistry and analytical approach for the removal of Brilliant Blue G (BBG) using the non-ionic poly(acrylate) resin Amberlite XAD7HP (XAD7HP), emphasizing structure–property–performance relationships relevant to the resin’s adsorption behavior. The UV–Vis method used for BBG quantification exhibited excellent linearity in the 10–30 mg/L range (R² = 0.9998). Batch adsorption experiments performed over 15–800 mg/L revealed a well-defined saturation profile, with the Langmuir model providing the best fit (R² = 0.9999) and indicating a monolayer capacity of 117 mg/g and highly favorable adsorption (R_L = 0.001). Kinetic evaluation showed rapid initial uptake followed by intraparticle diffusion, with the pseudo-second-order model offering the highest correlation (R² = 0.9811), while Weber–Morris analysis confirmed the contributions of both film and pore diffusion. FTIR-ATR analysis revealed only minor shifts (−1) in characteristic bands, confirming physisorption driven by hydrogen bonding, π–π interactions, dipole–dipole forces, and hydrophobic effects, without structural modification of the resin. SEM/EDX imaging demonstrated significant morphological changes after adsorption, including partial pore blockage and deposition of dye aggregates within the meso–macroporous network. XRD patterns confirmed the structural stability of the resin, while TG-DSC analysis highlighted its thermal robustness and suitability for reuse. Desorption studies showed that acidic–alcoholic systems (MeOH–HCl, EtOH–HCl) ensured the highest BBG recovery, supporting the regenerability of XAD7HP. Overall, the combined spectroscopic, kinetic, equilibrium, and morphological evidence demonstrates that XAD7HP is a stable, efficient, and reusable resin for BBG removal, offering a sustainable remediation pathway aligned with green analytical chemistry principles.

This study evaluates the adsorption, structural characterization, and regeneration performance of acrylic resin Amberlite XAD7HP (X7) for the removal of metformin (MET), an emerging pharmaceutical contaminant. MET concentrations after adsorption were quantified using the linear UV–Vis method at 232 nm (R² = 0.9998). Adsorption kinetics followed the pseudo-second-order model (R² =0.9881), and equilibrium data fitted the Langmuir isotherm, confirming monolayer adsorption. Desorption experiments showed that acidic media were ineffective (−1, the shift of the C=N vibration from 1628 cm⁻¹ to 1605 cm⁻¹, and the appearance of a new band at 1542 cm⁻¹, indicating hydrogen bonding and dipole–dipole interactions with the resin. SEM micrographs revealed a clear transition from the X7, rough morphology to a smoother, partially occluded surface after adsorption, consistent with pore filling by MET. EDX analysis further confirmed MET uptake through the appearance of a distinct N signal and increased O content, serving as elemental markers of drug adsorption. TG/DSC demonstrated enhanced thermal stability and modified decomposition profiles for the resin loaded with MET, while XRD patterns confirmed the amorphous nature of X7 and the absence of crystalline MET deposits, indicating molecular-level dispersion. The integrated analytical, structural, kinetic, and desorption results highlight the potential of desorbed acrylic resin as a sustainable material for mitigating pharmaceutical pollution in aquatic environments.

This study examines the adsorption and interaction mechanisms of Congo red (CR) immobilized onto maize stalk (MS) to form MS-CR material, used for the removal of Fe³⁺, Cr³⁺, and Mn²⁺ (Mⁿ⁺) from aqueous media. Initially, the MS was functionalized with CR, achieving adsorption capacities between 41.4 and 48.0 mg/g across pH 2–10, confirming the formation of hydrogen bonding and aromatic interactions, as indicated by the shift of the OH band from 3338.91 to 3335.54 cm⁻¹ and the appearance of characteristic azo–aromatic peaks (1601–1506 cm⁻¹) in the FTIR spectra. Stability tests showed that CR remains anchored to the lignocellulosic matrix even under 2 M HCl/NaOH. Subsequently, adsorption experiments revealed a strong pH dependence: at pH 10, removal efficiencies reached 93% for Mn²⁺, 89% for Fe³⁺, and 72% for Cr³⁺ at 2 mg/L, driven by surface deprotonation and enhanced electrostatic attraction. Increasing the initial metal concentration (1–10 mg/L) led to maximum adsorption capacities of 2.00 mg/g for Fe³⁺, 1.64 mg/g for Cr³⁺, and 1.46 mg/g for Mn²⁺. Desorption experiments identified 0.5 M HCl as the optimal regenerating agent, achieving 90–97% metal release. FTIR analysis of MS-CR–Mn²⁺ showed the disappearance of the 1243 cm⁻¹ carboxyl band and the emergence of a metal–oxygen vibration at 559.37 cm⁻¹, confirming adsorption via coordination to deprotonated carboxyl and phenolic groups. TG/DSC/DTG analysis demonstrated improved stability of MS-CR compared to native MS. SEM/EDX confirmed the presence of S, Na, and Mⁿ⁺. The combined spectroscopic, microscopic, and thermal evidence demonstrates that MS-CR operates as a robust, multifunctional adsorbent capable of Mⁿ⁺ retention, offering a sustainable solution for water treatment.

The release of persistent azo dyes into aquatic systems remains a critical environmental and toxicological concern due to their high chemical stability, resistance to biodegradation, and potential to generate carcinogenic aromatic amines. This study evaluates the adsorption of Amberlite XAD-4 (X4), a hydrophobic polystyrene–divinylbenzene resin, for the removal of the toxic azo dye Direct Red 23 (DR 23) from aqueous solutions. Batch experiments were performed to assess the influence of contact time and initial dye concentration, supported by kinetic and equilibrium modeling. Adsorption proceeded through a multistage mechanism involving thin-layer diffusion, intraparticle diffusion, and final equilibrium, which was reached after 48 h. The pseudo-second-order kinetic model (PSO) with R² = 0.9648 best described the adsorption behavior. Equilibrium data was fitted by the Langmuir isotherm (R² = 0.9990), yielding a maximum adsorption capacity of 56.8 mg g⁻¹, consistent with the experimentally observed saturation plateau. FTIR spectra revealed characteristic shifts in aromatic, –N=N– (≈1500 cm⁻¹), and –SO₃²⁻ (1180–1040 cm⁻¹) bands, which, corroborating the data provided by SEM/EDX analysis, completes the adsorption of DR 23 on the X4 matrix. TG/DSC analysis showed modifications in thermal behavior after adsorption without compromising resin stability, supporting strong dye–resin interactions. Overall, the integrated kinetic, isotherm, spectroscopic, and thermal analyses demonstrate that X4 is stable and an adsorbent with desorption capability using chemical agents, highlighting its potential for mitigating the environmental and toxicological risks associated with azo dye contamination in wastewater.

Pharmaceutical residues continue to increasingly contaminate water systems at a global level, and conventional wastewater treatment plants are unable to completely remove these emergent compounds. This study investigates the benzocaine adsorption from aqueous solutions onto Amberlite XAD-7 (X7) resin, with emphasis on quantitative performance metrics and mechanistic understanding. Adsorption occurred rapidly, reaching equilibrium within 60 min, with a maximum adsorption capacity (Q_e) of 140 mg/g and a Langmuir monolayer capacity of 147 mg/g. Experimental parameters strongly influenced X7 performance: resin dosage (0.01–0.05 g) and agitation speed (25–200 rpm) enhanced removal efficiency from 10% to 99.9%, while pH variation (5–9) had a negligible effect, confirming a predominantly hydrophobic, non-ionic adsorption mechanism. Equilibrium data are best described by the Langmuir model (R² = 0.9920, b = 5.2 L/mg, RL = 0.0003), indicating highly favorable monolayer adsorption, while kinetic behavior is described by the pseudo-second-order (PSO) model. FTIR-ATR analysis confirms benzocaine retention through characteristic shifts in aromatic, amine, and ester bands. TG/DSC measurements prove the thermal stability of X7 and the incorporation of benzocaine within the polymeric matrix. Desorption efficiencies ranged from 40% (NaOH) to 97% (HCl-ethanol mixture), demonstrating that X7 was regenerated under the tested conditions with a single cycle. Overall, X7 exhibits high capacity, robustness, and recyclability, highlighting its strong potential for efficient benzocaine removal from contaminated wastewater.

In this study, a novel material was obtained by functionalizing shredded maize stalk (MS) with Alizarine Red S (ArS), a complexing agent that contains −OH and −C=O groups in its structure (MS-ArS). The obtained MS-ArS was employed in adsorption studies for Mn²⁺, Pb²⁺, Cu²⁺, Cr³⁺, Zn²⁺, and Fe³⁺ (Mⁿ⁺) removal from mixed aqueous matrices. Initially, complex formation between (Mⁿ⁺) and ArS in buffer solution at pH 4 and 10 was investigated using the UV-Vis spectrometric method. Continuous, the functionalization process of MS with ArS was tested at several pH values (2, 4, 6, 8, and 10) using a batch technique. It was observed that the best functionalization of MS with ArS was obtained at pH = 2. Subsequently, Mⁿ⁺ adsorption onto the MS-ArS mass was tested separately at pH 4 and 10. The study achieved that Mⁿ⁺ adsorption proved to be pH dependent. The results confirmed that at pH = 10, Mⁿ⁺ adsorption was increased, compared with pH = 4. MS-ArS has affinity for Mⁿ⁺ in the following order Fe³⁺ > Cu²⁺ > Zn²⁺ > Mn²⁺ > Pb²⁺ > Cr³⁺. Experimental data revealed remarkable desorption rates when 0.5 M HCl was used. After five adsorption/desorption cycles of Mⁿ⁺, the removal capability of MS-ArS was preserved. Overall, the potential of MS-ArS for effective Mⁿ⁺ removal/reuse makes it a sustainable polymer for wastewater treatment applications.

In this study, a novel material obtained from shredded maize stalk (MS) was functionalized using Alizarine Red S (ArS), a complexing agent that contains -OH and -C=O groups in its structure (MS-ArS). The obtained material MS-ArS was employed in adsorption experiments for Mn²⁺, Pb²⁺, Cu²⁺, Cr³⁺, Zn²⁺ and Fe³⁺ (Mⁿ⁺) removal. Initially, complex formation between (Mⁿ⁺) and ArS in buffer solution at pH 4 and 10 was investigated using UV-Vis spectrometric method. The functionalization process of MS was done at pH = 2, 4, 6, 8, and 10. The results showed that the best functionalization was obtained at pH=2. After functionalization study, Mⁿ⁺ adsorption onto MS-ArS at pH 4 and 10 was tested. Mⁿ⁺ adsorption proved to be pH dependent. It was observed that pH=10 was the optimum medium for Mⁿ⁺ adsorption. MS-ArS has affinity for Mⁿ⁺ in the following order Fe³⁺>Cu²⁺>Zn²⁺>Mn²⁺>Pb²⁺>Cr³⁺. The results demonstrate also remarkable desorption rates (D(%)) when 0.5 M HCl is used as regeneration solvent: 94% for Cu²⁺, 92.4% for Fe³⁺, 91.7% for Cr³⁺, 90.8% for Zn²⁺, 90.3% for Pb²⁺, and 86.1% for Mn²⁺. These findings highlight the potential of this sustainable material for effective adsorption and recovery of the complexing material in order to respect the principle of circular economy approach.

Drinking and wastewater are to be treated for safe human consumption and for keeping surface waters clean. There are multiple water purification procedures, but the use of ion-exchange resins significantly enhances water purification efficiency. This review was targeted on highlighting the concept and classification of polymeric ion-exchange resins as well as pointing out their real-world applications. Their successful use for purification purposes has been linked to their chemical structure, simplicity of operation, accessibility, and reusability. Therefore, polymeric ion-exchange resins have been used for the removal of a wide range of organic and inorganic pollutants such as pharmaceutical compounds, dyes, organic matter, metals, and many others. Ion-exchange resins are obtained directly by synthesis methods or grafting ionizable groups on polymer matrix in order to ensure continuous improvement. Furthermore, the newly designed ion-exchange resins take into consideration biodegradability potential towards obtaining ecofriendly compounds.

Sewage sludge (SS) resulting from wastewater treatment plants (WWTP) is commonly applied worldwide as a fertilizer in agriculture. This can be done following a rigorous analysis of the sewage sludge composition. Due to its toxic potential, heavy metal ion content is one of the key parameters to test when evaluating SS sample usage as fertilizer. The distribution of metals present in SS samples produced by five municipal WWTPs in Romania was studied. To obtain information regarding metal distribution in SS, a modified ultrasound-assisted extraction procedure of the Community Bureau of Reference (BCR) was employed for As, Cd, Cr, Cu, Mo, Ni, Pb, Zn, and Co quantitation. Concentrations of these metals were measured using ICP-EOS spectrometry. Method extraction accuracy was verified using CRM-483 certified reference material. Results show that extraction efficiency was lowest for the exchangeable fraction for all studied metals. The detected ion metals were found distributed in fractions (F) 2, 3 and 4, which are unavailable for plants and groundwater under natural environmental conditions. One noteworthy finding was that using ultrapure water for the leachate test resulted in low metal solubility, indicating slight metal desorption in real environmental samples. Furthermore, maize stalk bio-adsorbent was used to minimize metal ion content in WWTP leachate samples produced by the storage of SS in terms of metal ion adsorption.

A high-performance liquid chromatography with diode array detector (HPLC-DAD) analytical method was developed for the simultaneous detection of 17 phenolic compounds, including phenols, chlorophenols, alkylphenols, and nitrophenols, in two types of water matrices: wastewater and surface water. Prior to HPLC-DAD determination, a solid-phase extraction (SPE) procedure was optimized. The proposed method uses multiwavelength analysis, with the optimum detection wavelengths selected as 268 nm, 280 nm, 386 nm, 304 nm, and 316 nm. The highest resolution was achieved using a chromatographic column, Eclipse XDB-C18 (150 × 4.6 mm, 5 μm), which was kept at 20 °C. The mobile phase consisted of a gradient elution program, with mobile phase A being a 0.1% H₃PO₄ aqueous solution and mobile phase B being acetonitrile. The flow rate was set at 0.6 mL/min. The 17 target phenolic compounds were fully separated in less than 27 min. All compounds showed good linear regression, with correlation coefficients higher than 0.999. The method’s quantitation limits ranged from 4.38 to 89.7 ng/L for surface water and 7.83 to 167 ng/L for wastewater. The recovery rates were in the range of 86.2–95.1% for surface water and 79.1–86.3% for wastewater. The SPE-HPLC-DAD method was proven to be fast, sensitive, accurate, and reproducible. The developed method was successfully applied for the analysis of the 17 phenolic compounds in real surface water and wastewater samples, with phenol, 2,4-DNP, and 2,4-DNP being determined at levels greater than the method’s limits of quantitation (LOQs). The proposed analytical method represents an original technical resource for the simultaneous determination of 17 phenolic compounds in environmental water matrices.