Sandeep Kumar Tiwari

Electrospun chitosan–polyvinyl alcohol composite nanofibers loaded with cerium for efficient removal of arsenic from contaminated water

Contamination of water due to arsenic has been extensively reported all over the world. It has led to massive epidemics of arsenic poisoning. An urgent need is being felt to develop efficient techniques for the removal of arsenic from contaminated water. In this context, cerium (Ce) loaded chitosan (CHT)–polyvinyl alcohol (PVA) composite (Ce-CHT/PVA) nanofibers were developed by electrospinning technique and have been employed for removing As(III). The Ce-CHT/PVA composite nanofibers efficiently adsorb As(III) and purify water below the prescribed limit of WHO/EPA. As(III) adsorption over the surface of Ce-CHT/PVA has been confirmed by scanning electron microscopy and energy dispersive X-ray spectroscopy (SEM-EDAX), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). The quantitative estimation of As(III) has been carried out by flameless atomic adsorption spectrophotometer-hydride generator (AAS-HG) system. The As(III) adsorption efficiency of Ce-CHT/PVA composite nanofibers has been established as a function of pH, time, temperature and adsorbent dose. The adsorption data were best fitted to Langmuir isotherm, and the maximum adsorption capacity (qm) was found to be 18.0 mg g−1. The interference studies of several ionic species individually as well multi-element for As removal have also reported. The measurement of the uncertainty of As(III) determination was calculated after determining the contributing factors. The data are reported with a confidence level of 95% (K = 2). The Ce-CHT/PVA composite nanofibers are non toxic and can be directly used for water purification or after being embedded in the form of membrane or candles.

Surface Engineered Zeolite: An Active Interface for Rapid Adsorption and Degradation of Toxic Contaminants in Water

Zeolite has been surface modified to form novel multifunctional materials having capability for simultaneous and facile removal of heavy metals [Pb(II)], organic pollutants [methylene blue dye], and microorganisms [E. Coli, S. Aureus, and Pseudomonas] from contaminated water. The unique concept involves formation of core-shell particles with a functional core of zeolite and a porous shell of ZnO nanoflakes which not only imparts photocatalytic and antibacterial properties but also renders the surface negatively charged, thereby facilitating rapid adsorption of Pb(II) and MB. The uniform formation of ZnO nanoflakes (shell) on the zeolite (core) surface has been confirmed by XRD, DRS, FE-SEM, and TEM studies. Metal ion adsorption studies under varying conditions of time and concentration indicate that the material follows the Langmuir isotherm model and pseudo-second-order kinetics with good correlation to the experimental data. The rapid and high adsorption capacity of the material for both Pb (II) and MB has been established while factors responsible for enhanced adsorption have been discussed. The antibacterial studies against Gram negative bacteria (E. Coli and Pseudomonas) and Gram positive bacteria (S. Aureus) showed good zone inhibition characteristics. The material can be regenerated and reused besides having ease of separation using simple techniques. Being multifunctional, efficient, nontoxic, energy neutral, and recyclable with no effluent generation, the material is an efficient and sustainable alternative for water purification.

Cerium functionalized PVA–chitosan composite nanofibers for effective remediation of ultra-low concentrations of Hg(II) in water

Mercury contaminated drinking water significantly affects the central nervous system, kidneys and other organs in humans even at very low concentration. Higher concentration of mercury are reported to be effectively removed by adsorption and precipitation techniques. Reverse osmosis (RO) is a better known technique used for the removal of low concentration of Hg (<200 ppb). However, its limitations include low flux, high water rejection, high capital cost, in addition to being power dependent. The present study reports the fabrication of low cost, biodegradable, electrospun cerium functionalized PVA–chitosan (Ce–PVA–CHT) composite nanofibers for the effective removal of low concentrations of Hg(II) present in water. It adsorbs Hg(II) and purifies water up to safe potable limits as prescribed by WHO/US-EPA. The adsorption of Hg(II) over the surface of Ce–PVA–CHT is confirmed by SEM/EDAX, FTIR, XRD and XPS techniques. The adsorption studies are reported by varying parameters, viz. time, pH, adsorbent dose and varying contents of Ce in PVA–CHT nanofibers. Traceability is established by using SCP Science-U.K. made certified reference standard for the calibration of AAS-HG used for the determination of Hg(II). The kinetic data shows fast and efficient removal of Hg(II) and indicates to follow pseudo second order kinetics. The adsorption data is best fitted to the Langmuir isotherm and indicates monolayer adsorption of Hg(II).