Methionine-functionalized graphene oxide/sodium alginate bio-polymer nanocomposite hydrogel beads: Synthesis, isotherm and kinetic studies for an adsorptive removal of fluoroquinolone antibiotics

This work was supported by Pt. Ravishankar Research Fellowship Scheme, Raipur, Chhattisgarh, India (grant number V.R. No. 3114/4/Fin./Sch.//2018). This work was also supported by national funds through FCT-Fundacao para a Ciencia e a Tecnologia, I.P., under the Scientific Employment Stimulus-Institutional Call (CEECINST/00102/2018) and by the Associate Laboratory for Green Chemistry-LAQV, financed by national funds from FCT/MCTES (UIDB/50006/2020 and UIDP/50006/2020).In spite of the growing demand for new antibiotics, in the recent years, the occurrence of fluoroquinolone antibiotics (as a curative agent for urinary tract disorders and respiratory problems) in wastewater have drawn immense attention. Traces of antibiotic left-overs are present in the water system, causing noxious impact on human health and ecological environments, being a global concern. Our present work aims at tackling the major challenge of toxicity caused by antibiotics. This study deals with the efficient adsorption of two commonly used fluoroquinolone (FQ) antibiotics, i.e., Ofloxacin (OFX) and Moxifloxacin (MOX) on spherical hydrogel beads generated from methionine‒functionalized graphene oxide/ sodium alginate polymer (abbreviated Met-GO/SA) from aqueous solutions. The composition, morphology and crystal phase of prepared adsorbents were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), Fourier transform infrared spectroscopy (FTIR), high-resolution transmission electron microscopy (HR-TEM) and thermogravimetric analysis/differential thermogravimetry (TGA/DTG). Batch adsorption tests are followed to optimize the conditions required for adsorption process. Both functionalized and non-functionalized adsorbents were compared to understand the influence of several experimental parameters, such as, the solution pH, contact time, adsorbent dosage, temperature and initial concentration of OFX and MOX on adsorption. The obtained results indicated that the functionalized adsorbent (Met-GO/SA) showed a better adsorption efficiency when compared to non-functionalized (GO/SA) adsorbent. Further, the Langmuir isotherm was validated as the best fitting model to describe adsorption equilibrium and pseudo second-order-kinetic model fitted well for both types of adsorbate. The maximum adsorption capacities of Met-GO/SA were 4.11 mg/g for MOX and 3.43 mg/g for OFX. Thermodynamic parameters, i.e., ∆G°, ∆H° and ∆S° were also calculated. It was shown that the overall adsorption process was thermodynamically favorable, spontaneous and exothermic in nature. The adsorbents were successfully regenerated up to four cycles with 0.005 M NaCl solutions. Overall, our work showed that the novel Met-GO/SA nanocomposite could better contribute to the removal of MOX and OFX from the liquid media. The gel beads prepared have adequate features, such as simple handling, eco-friendliness and easy recovery. Hence, polymer gel beads are promising candidates as adsorbents for large-scale water remediation.publishersversionpublishe

A simple sensitive spectrophotometric method for determination of dichlorvos in environmental samples

96-98A sensitive method has been developed for spectrophotometric determination of an organophosphorous pesticide dichlorvos, also known as 2,2 dichlorovinyl methyl phosphate or dichlorophos. The method is based on hydrolysis of dichlorvos by sodium hydroxide to produce dichloroacetaldehyde, which on coupling with phloroglucinol in alkaline medium, gives orange colour. The orange dye shows absorption maxima at 475 nm and obeys Beer's law in the range of 10-100μg/25 mL (0.4 to 4 ppm) of solution. The molar absorptivity and Sandell's sensitivity were found to be 4.53×104 l mol-1cm-1 and 0.0048 μg cm-2 respectively. The method has been successfully applied for the determination of dichlorvos in water, agricultural soil and vegetables

Novel glycine-functionalized magnetic nanoparticles entrapped calcium alginate beads for effective removal of lead

The magnetic Fe3O4 nanoparticles were functionalized with glycine at pH 6. The glycine functionalized magnetic nanoparticles (GFMNPS) were then entrapped into alginate polymer as beads and used as adsorbent for the re- moval of Pb(II) ions. The developed adsorbents were characterized by Fourier transform infrared spectroscopy, vibrating sample magnetometer and scanning electron microscopic analysis. The surface of beads contain amino and carboxylate groups which make them effective adsorbents for the removal of Pb(II) ions. The adsorp- tion of Pb(II) ions from aqueous solution was found to be highly pH dependent. 92.8% Pb(II) was removed just in 10 min. The kinetic data fitted well with pseudo second order model and the equilibrium was reached in 100 min with 99.8% removal of Pb(II) ions from aqueous solution. The adsorption isotherm strictly followed Langmuir model with the maximum adsorption capacity of 555.5 mg/g of the adsorbent. The thermodynamic study con- firmed that the adsorption was spontaneous and endothermic in nature. The adsorbent could be regenerated four times simply by 0.2 M HNO3 retaining 90% of the adsorption capacity. The synthesized adsorbent was found to be eco-friendly, cost-effective, efficient and superior over other polymer based adsorbents for removal of Pb(II) ions from aqueous solution

A micellar mediated novel method for the determination of selenium in environmental samples using a chromogenic reagent

A novel, simple, sensitive and rapid spectrophotometric method for the determination of selenium(IV) in an acidic medium using rhodamine B hydrazide (RBH) has been developed. The method is based on the micellar mediated oxidation of RBH by Se(IV) in an acidic medium to produce a pinkish violet color of rhodamine B, which was monitored spectrophotometrically at λmax 585 nm. The sensitivity of the method was found to increase when the reaction was performed in a micellar medium. Beer's law was obeyed in the concentration range of 0.002–0.032 μg mL−1. The reaction variables such as time, temperature, reagent concentration, and acidity have been optimized for the reaction. Sandell's sensitivity and molar absorptivity for the reaction system were found to be 0.00004 μg cm−2 and 42.52 × 106 L mol−1 cm−1, respectively. The developed method was successfully applied for the determination of Se(IV) in several real samples with quantitative results

Intensified elimination of aqueous heavy metal ions using chicken feathers chemically modified by a batch method

UIDB/50006/2020Modified chicken feathers (MCFs) were used as adsorbents for the removal of Co(II), Cu(II), Fe(II) and Ni(II) heavy metal ions from water by varying pH, adsorbent concentration and time. MCFs were characterized using Fourier Transform Infrared (FTIR) spectroscopy, Scanning Electron Microscopic (SEM) analysis, Energy Dispersive X-ray (EDX) spectroscopy, Adsorption of N2 at −196 °C, Thermogravimetric analysis (TGA) and X-ray Diffraction (XRD) analysis. The adsorption isotherm for the metal ions could be well explained by the Langmuir model. The maximum adsorption capacities were 200.0, 50.0, 43.47, and 4.85 mg/g, following the sequence: Cu(II) > Co(II) > Fe(II) > Ni(II), respectively. Removal efficiencies of Co(II), Cu(II), Fe(II) and Ni(II) ions were 98.7%, 98.9%, 98.7% and 99%, respectively, for 20 mg/L concentration. The study of the adsorption kinetics for metal ions on MCFs confirmed that the process followed a pseudo second order kinetic model in all cases. The thermodynamics showed that the adsorption processes for metal ions adsorption on MCFs were spontaneous and endothermic. MCFs exhibited a good recyclability and high adsorption efficacy after 7 cycles using a 0.1 M EDTA solution, maintaining 90% of the adsorption ability.authorsversionpublishe