Optimization of Arsenic Removal from Aqueous Solutions Using Amidoxime Resin Hosted by Mesoporous Silica

Glycine-Group-Functionalized Polymeric Materials Impregnated with Zn(II) Used in the Photocatalytic Degradation of Congo Red Dye

Reducing the ecological impact of dyes through wastewater discharge into the environment is a challenge that must be addressed in textile wastewater pollution prevention. Congo red (CR) dye is widely used in experimental studies for textile wastewater treatment due to its high organic loads used in its preparation. The degradation of organic dyes of the CR type was investigated using the photocatalytic activity of functionalized polymers. We have employed photodegradation procedures for both polymer-supported glycine groups (Code: AP2) and polymer-supported glycine-Zn(II) (Code: AP2-Zn(II)). A photocatalysis efficiency of 89.2% was achieved for glycine pendant groups grafted on styrene-6.7% divinylbenzene copolymer (AP2) and 95.4% for the AP2-Zn(II) sample by using an initial concentration of CR of 15 mg/L, a catalyst concentration of 1 g/L, and 240 min of photocatalysis. The findings provided here have shown that the two materials (AP2 and AP2-Zn(II)) may be effectively employed in the heterogeneous photocatalysis method to remove CR from water. From the perspective of the degradation mechanism of CR, the two photocatalysts act similarly.

Chemical Modification of Acrylonitrile-Divinylbenzene Polymer Supports with Aminophosphonate Groups and Their Antibacterial Activity Testing

Bacterial contamination is a major public health concern on a global scale. Treatment resistance in bacterial infections is becoming a significant problem that requires solutions. We were interested in obtaining new polymeric functionalized compounds with antibacterial properties. Three components (polymeric amine, aldehyde, and phosphite) were used in the paper in a modified "one-pot" Kabachnik-Fields reaction, in tetrahydrofuran at 60 °C, to create the N-C-P skeleton in aminophosphonate groups. Two copolymers were thus prepared starting from an acrylonitriledivinylbenzene (AN-15%DVB) copolymer containing pendant primary amine groups modified by grafting aminophosphonate groups, i.e., aminobenzylphosphonate (Bz-DVB-AN) and aminoethylphosphonate (Et-DVB-AN). The two copolymers were characterized by FT-IR spectroscopy, SEM-EDX, TGA, and antibacterial properties. It was shown that the novel products have antibacterial qualities against S. aureus and E. coli bacteria. The sample with the strongest antibacterial activity was Et-DVB-AN. We assessed how well the Weibull model and the first-order kinetic model represent the inactivation of microbial cells in our samples. The main advantage of the new antibacterial agents developed in this work is their easy recovery, which helps to avoid environmental contamination.

UV-radiation manufacturing of natural macromolecular products salecan and tannic acid-based functional gel material as superadsorbent for toluidine blue remediation

Adsorbent materials constructed from natural macromolecular products are favored because of their wide range of sources, biodegradability, and environmental friendliness. Salecan is a novel extracellular polysaccharide with ideal physicochemical and biological activities. Here, we have designed a polymer gel through UV-initiated polymerization of [2-(Methacryloyloxy) ethyl] dimethyl-(3-sulfopropyl) ammonium hydroxide (SBMA) in the mixture of salecan and tannic acid. Photopatterned polymerization process allowed in situ formation of gel adsorbent in a mild reaction condition with energy-efficient manner. Batch experiments for toluidine blue (TB) adsorption were carried out as a function of initial dye concentration, solution pH, contact time, and gel dosage to examine the adsorption capacity, potential mechanism, and removal efficiency. Adsorption behavior exhibited a pH-dependence pattern, which was closely related to their swelling and morphological properties. Adsorption process was in conformity to pseudo-second-order kinetic and Langmuir isotherm models, unlocking a chemical adsorption behavior and monolayer-type removal. The maximum adsorption was 490.2 mg/g, which could be considered a superiorly competing value. Additionally, the UV-gel still showed desirable recyclability and maintained the adsorption effectiveness over 95 % after five regeneration cycles. This study opened up new prospects in preparing high performance adsorbent for TB decontamination and laid the foundation for polysaccharide-based adsorption material research.

Synthesis of amidoxime adsorbent prepared by radiation grafting on upcycled low-density polyethylene sheet for removal of heavy metals from wastewater

The issue of discharging waste, especially heavy metals from industrial activities into the environment, not only adversely impacts environmental quality but also has impacts on communities and human health. Removal and reduction of heavy metal contamination in rivers and wastewater are, therefore, critical initiatives that require significant attention. This work studied the removal of heavy metals, including Zn(II), Cu(II), As(III), and Pb(II) by utilizing an upcycled amidoxime low-density polyethylene sheet (AO-sheet). The synthesized AO-sheet was analyzed for various physical properties, including scanning electron microscope, energy-dispersive x-ray spectroscopy, Fourier transform infrared spectroscopy, and thermogravimetric analysis. For the batch adsorption experiment, parameters affecting adsorption capacity were studied: initial concentration, submerging time, and pH. Adsorption isotherms were also studied. The results of the heavy metal adsorption study showed that the initial concentration was the most significant parameter; the higher the initial concentration, the greater the adsorption capacity. The adsorption capacity of Zn(II) and Pb(II) increased with submersion time, which achieved 21.07 and 0.855 mg/g-adsorbent, respectively, after four weeks of submersion under the highest initial concentration studied. The adsorption capacity of Cu(II) was 7.98 mg/g-adsorbent after two weeks of optimal adsorption duration under the highest initial concentration studied. The adsorption capacity of As(II) was 1.07 mg/g-adsorbent after one week of optimal submersion time under the highest initial concentration studied. Moreover, the appropriate pH range for effective adsorption of Zn(II), Cu(II), and Pb(II) was identified as 8-9, while for As(III), it was 6-8, with an adsorption duration of 0.43 weeks (3 days). From the Langmuir isotherm, it was found that the adsorption of this work was characterized by monolayer adsorption. The results demonstrate that the AO-sheet can be effectively used to remove heavy metals from wastewater. Its potential for reusability was up to 8 cycles, with the Zn(II) adsorption capacity being reduced to about 20.37%.

Ionic Liquid Modified Polymer Gel for Arsenic Speciation

A new ionic liquid modified polymer gel containing methylimidazolium groups (poly(MIA)) is proposed as a sorbent for the separation and enrichment of trace inorganic and organic arsenic species in surface waters. The poly(MIA) was synthesized by chemical modification of polymeric precursor using post-polymerization modification of poly(glycidyl methacrylate-co-trimethylolpropane trimethacrylate). The composition, structure, morphology, and surface properties of the prepared particles were characterized using elemental analysis, Fourier transform infrared spectroscopy, scanning electron microscopy, and nitrogen adsorption-desorption measurements. Optimization experiments showed that at pH 8, monomethylarsonic acid (MMAs), dimethylarsinic acid (DMAs), and As(V) were completely retained on the poly(MIA), while the sorption of As(III) was insignificant. The desorption experiments revealed that due to the weaker binding of organic arsenic species, selective elution with 1 mol/L acetic acid for MMAs + DMAs, followed by elution with 2 mol/L hydrochloric acid for As(V), ensured their quantitative separation. The adsorption kinetic and mechanism were defined. The analytical procedure for As(III), As(V), MMAs, and DMAs determination in surface waters was developed and validated through the analysis of certified reference material.

Green wastewater treatment of repurposed COVID-19 therapy (levofloxacin) using synthesized magnetite pectin nanoparticles, comparison with mesoporous silica nanoparticles

RATIONALE

Antibiotics have been detected worldwide in the aquatic environment. Moreover, certain classes of antibiotics have been repurposed for the management of COVID-19, which increased their use and presence in wastewater. Their occurrence even in low concentrations leads to the development of antibiotic resistance.

METHODOLOGY

Magnetite pectin nanoparticles (MPNP) were fabricated and compared to an established model of mesoporous silica nanoparticles (MSNP). Our studied adsorbate is levofloxacin, a fluoroquinolone antibiotic, commonly used in managing COVID-19 cases.

RESULTS

The influence of various factors affecting the adsorption process was studied, such as pH, the type and concentration of the adsorbent, contact time, and drug concentration. The results illustrated that the optimum adsorption capacity for antibiotic clearance from wastewater using MPNP was at pH 4 with a contact time of 4 h; while using MSNP, it was found to be optimum at pH 7 with a contact time of 12 h at concentrations of 10 µg/mL and 16 g/L of the drug and nanoparticles, respectively, showing adsorption percentages of 96.55% and 98.89%. Drug adsorption equilibrium data obeyed the Sips isotherm model.

DISCUSSION AND CONCLUSION

HPLC assay method was developed and validated. The experimental results revealed that the MPNP was as efficient as MSNP for removing the antibacterial agent. Moreover, MPNP is eco-friendly (a natural by-product of citrus fruit) and more economic as it could be recovered and reused. The procedure was evaluated according to the greenness assessment tools: AGREE calculator and Hexagon-CALIFICAMET, showing good green scores, ensuring the process's eco-friendliness.

Mesoporous Materials for Metal-Laden Wastewater Treatment

Rapid technological, industrial and agricultural development has resulted in the release of large volumes of pollutants, including metal ions, into the environment. Heavy metals have become of great concern due to their toxicity, persistence, and adverse effects caused to the environment and population. In this regard, municipal and industrial effluents should be thoroughly treated before being discharged into natural water or used for irrigation. The physical, chemical, and biological techniques applied for wastewater treatment adsorption have a special place in enabling effective pollutant removal. Currently, plenty of adsorbents of different origins are applied for the treatment of metal-containing aqueous solution and wastewater. The present review is focused on mesoporous materials. In particular, the recent achievements in mesoporous materials' synthesis and application in wastewater treatment are discussed. The mechanisms of metal adsorption onto mesoporous materials are highlighted and examples of their multiple uses for metal removal are presented. The information contained in the review can be used by researchers and environmental engineers involved in the development of new adsorbents and the improvement of wastewater treatment technologies.