Ultra-sensitive detection and scavenging of arsenic ions and ciprofloxacin using 3D multipurpose hemicellulose based aerogel: Adsorption mechanism and RSM optimization.

Trace level detection and efficient removal of arsenite ions (As (III)) and ciprofloxacin (CPR) antibiotic was achieved using hemicellulose based ratiometric fluorescent aerogel. Hemicellulose derived from rice straw was oxidised to dialdehyde hemicellulose followed by crosslinking using chitosan via a Schiff base reaction (C = N) yielding a highly porous 3D fluorescent aerogel (CS@DAHCA). Various factors governing adsorption were analyzed by applying response surface methodology (RSM) approach. CS@DAHCA exhibited ultra-trace level monitoring with the limit of detection of 3.529 pM and 55.2 nM for As (III) and CPR, respectively. The CS@DAHCA showed maximum adsorption capacity of 185 µg g-1 and 454 mg g-1 for As (III) and CPR, respectively. Finally, the feasibility of CS@DAHCA was ascertained for real water samples confirming it as promising candidate for remediation of As (III) and CPR.

Bioremediation of multifarious pollutants using laccase immobilized on magnetized and carbonyldiimidazole-functionalized cellulose nanofibers.

An easily recyclable biocatalyst (Lac@CDI-MCNFs) was synthesized by immobilizing laccase on rice straw-derived carbonyldiimidazole mediated magnetized cellulose nanofibers (MCNFs). Lac@CDI-MCNFs were utilized for bioremediation of cefixime antibiotic (CT), carbofuran pesticide (CF) and safranin O dye (SO) via oxidation-reduction reactions in wastewater. MCNFs provided enhanced pH, temperature and storage stability to laccase and allowed reusability for up to 25 cycles with mere 20 % decline in efficacy. The Lac@CDI-MCNFs effectively degraded 98.2 % CT and 96.8 % CF into benign metabolites within 20 h and completely degraded SO in just 7 h. Response surface modelling (RSM) was employed based on the Box Behnken Design to evaluate the effect of various parameters i.e. pH, catalyst dosage and the pollutants concentration which was further validated with experimental studies. The degradation products were identified using LCMS, which allowed the degradation pathway of the pollutants to be determined. The degradation of all pollutants followed first- order kinetics with rate constants of 0.1775, 0.0832 and 0.958 h-1 and half-life of 3.9, 5.0 and 0.723 h for CT, CF and SO, respectively. Lac@CDI-MCNFs was demonstrated to be an effective catalyst for the degradation of multifarious pollutants.

Diamidoximated cellulosic bioadsorbents from hemp stalks for elimination of uranium (VI) and textile waste in aqueous systems.

Selective abolition of hazardous U(VI) ions from nuclear power plants and removal of toxic colorants from textile industries pose great challenge. The work aims to develop cellulosic bioadsorbents from waste stalks of local weed, Cannabis sativa, commonly known as hemp. Cellulose nanofibers (PCFs) were chosen as substrates owing to their unique characteristics like surface hydroxyl groups, large surface to volume ratio and excellent mechanical properties. PCFs were isolated from hemp stalks and their structural characterization using FTIR, TGA and XRD ensured retrieval of pure crystalline cellulose. PCFs were modified via copolymerization to obtain diaminomaleonitrile adorned cellulose grafts (DAMNC) and further converted to get diamidoxime functionalized cellulose (DAOC). DAOC exhibited exceptional affinity with uranium (VI) ions, safranin-o and methylene blue dyes due to presence of two amidoxime groups. Sorption capability was ascertained for optimization of parameters like contact time, pH selectivity, adsorbent dosage and concentration. Sorption followed Pseudo second-order kinetic model with maximum sorption of 220 mg/g, 19.01 mg/g and 46.4 mg/g for U(VI) ions, SO and MB, respectively. EDX mapping revealed uniform adsorption of all the three pollutants on DAOC while XPS ascertained that the sorption originated from multiple interactions between the adsorbent and the pollutants.

Green and novel adsorbent from rice straw extracted cellulose for efficient adsorption of Hg (II) ions in an aqueous medium.

Cellulose nanofibrils (CNF) were extracted from rice straw, a waste lignocellulosic biomass, using soda cooking, which resulted in a reduction of the recalcitrance of biomass, leading to hydrolysis of hemicellulose into sugars, which was subsequently washed, leaving a residue of cellulose. FTIR confirmed the removal of lignin and hemicellulose to yield pure CNF while XRD, DTG and TGA results showed increased crystallinity and thus higher thermal stability. CNFs were functionalized using l-methionine, a natural amino acid, to graft sulfides and amino functional groups onto the surface of fibers. Structural and morphological changes induced by grafting were confirmed by FTIR, XRD, TEM, Mapping and Elemental analysis. Modified fibers exhibited a high adsorption capacity of 131.86 mg/g for Hg (II) ions even at low concentration i.e. 300 ppm owing to sulfides. Optimization of pH on adsorption behavior was established through extensive pH studies and adsorption kinetics. Adsorption follows pseudo second order kinetic model indicating chemisorption for removal of Hg (II) ions from simulated wastewater.