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Phenol formaldehyde (PF) resins are one of the oldest synthesized and very widely used resins. Their properties can be improved with the incorporation nano-fillers even with lower loadings. Graphene materials have attracted significant attention in recent years owing to its exceptional thermal, mechanical and electrical properties. Herein, we report a very simple and effective way to reduce graphene oxide (GO) by using highly abundant potato starch instead of conventionally used toxic and hazardous reducing agents like hydrazine. The reduced GO (RGO) is then effectively incorporated into PF resin by optimizing various processing parameters. The reinforcing effect of RGO sheets on the PF matrix was investigated by X-ray diffraction (XRD) and Transmission Electron Microscopy (TEM). The effect of RGO on thermal properties of the polymer nanocomposites was studied using Thermogravimetric Analysis (TGA). The mechanical properties of PF/RGO composites were studied by tensile and Izod impact tests. The fracture mechanism of the composites was investigated by Scanning Electron Microscopy. Theoretical prediction of the mechanical properties of the nanocomposites using Halpin-Tsai models gave sufficient information regarding the orientation of graphene sheets in PF matrix.

Nanotechnology was utilized for remediation of heavy metals and pesticide residues from soil. Nanobased phytoremediation technology has been widely followed in recent years as an in situ, cost-effective potential strategy for the cleanup of heavy metals from contaminated sites. The present study discusses the use of therrestrial plant species such as Catharanthus roseus, Tradescantia spathacea, and Alternanthera dentate to decontaminate the soil using phytoremediation and enhanced phytoremediation techniques using nanozerovalent iron particles. The results of the study indicated that the application of nanoparticles to soil significantly enhanced Pb, Ni, and Cd removal using the selected plant species. In the particular experiment, within 45 days of enhanced phytoremediation study, the removal efficiency of Pb, Ni, and Cd (with an initial concentration of 100 mg kg−1 of Pb, 55.0 mg kg−1 of Ni and 50.0 mg kg−1 of Cd) was enhanced to 97.20%, 76.47%, and 71.50%, respectively, for C. roseus, 93.20%, 73.18%, and 73.60%, respectively, for T. spathacea and 92.50%, 80.0%, and 76.80%, respectively, for A. dentate. Thus nanophytoremediation techniques using selected plant species proved to be an efficient, environment-friendly method for the removal of heavy metals.

A bioreactor system that consisted of Pseudomonas fluorescens cells immobilised in calcium-alginate beads was utilised to remediate endosulphan contaminated water and soil. A packed bed reactor system was designed for the bio-degradation of endosulphan in artificially spiked water samples (initial concentration of endosulphan: 350 µg/L). Reactor studies with cell-immobilised Ca-alginate beads were conducted after checking their efficiency through batch and column degradation studies. The results showed that the concentration of toxic isomers of endosulphan (endosulphan alpha and endosulphan beta) was below the limit in the bioreactor during the 7th day of the experiment. Experiments conducted with contaminated soil samples (initial concentration of endosulphan: 1,000 μg/kg) indicated that the toxic isomers of endosulphan degraded to below the detection limit within 10 days and monitoring of endosulphan residues on the 14th day revealed that almost complete degradation of metabolites of endosulphan had occurred. The bioreactor system designed can be scaled up for remediation of endosulphan in contaminated areas.

The endosulfan-degrading bacterial strain Pseudomonas fluorescens was isolated, and degradation of endosulfan by freely suspended and calcium-alginate entrapped bacterial cells were investigated in batch as well as in packed bed column studies. Freely suspended Pseudomonas fluorescens cells with biomass maximum OD/OD0 value of 1.68 at 610 nm could degrade endosulfan with an initial concentration of 350.24 ± 0.83 μg/L efficiently within 12 days, thus utilising endosulfan as the sole carbon and energy source. Degradation of endosulfan occurred concomitantly with bacterial growth. The bacteria immobilised in Ca-alginate beads in batch shake flask system were tested for their ability to degrade endosulfan at different concentrations (350.24 ± 0.83, 450.39 ± 1.95 and 550.85 ± 1.84 μg/L). A total of 125 mL of Broth minimal medium of pH 7 was inoculated with 5 g of wet Ca-alginate beads (derived from a 3-mL cell suspension of 0.72 OD at 610 nm) for the study. Almost similar trends of degradation efficiencies were shown by the immobilised cells toward different concentrations of endosulfan. The complete removal of alpha and beta-isomers of endosulfan at different initial endosulfan concentrations was observed between 9 and 11 days of the experiment. Additionally, the degradation rate in batch reactors with Ca-alginate-immobilised cells also derived from a 3-mL cell suspension of 0.72 OD at 610 nm was tested and found to be marginally higher than that of free cells. Ca-alginate immobilised cells in packed bed reactors operated in a semi-continuous mode could degrade toxic alpha and beta-isomers of endosulfan (350.38 ± 1.18 μg/L) within 6 days. Thus, the method proved effective for biodegradation of endosulfan. The metabolites formed indicated that the degradation of the pesticide follows a hydrolytic pathway.

Nanoremediation technology holds enormous potential for the cleanup of hazardous pollutants. Here we report a study on the combined use of nano- and phytotechnology for the removal of chlorinated pesticides and heavy metals. The decomposition of endosulfan in the soil samples by nanophytoremediation was confirmed by gas chromatography followed by mass spectrometry. Of the different plants used in the presence of zero-valent iron nanoparticles (nZVI), A.calcarata was determined to have the best efficiency of removal and also found that the efficiency decreased in the order A. calcarata > O. sanctum > C. citratus. The nZVI endosulfan degradation mechanism appears to involve hydrogenolysis and sequential dehalogenation, which was confirmed by GC-MS analysis. Experiments were also conducted for the removal of Pb and Cd using Tradescantia spathacea (boat lily) and Alternanthera dentate. The analysis of heavy metals by ICP indicated that the plants with nZVI particles accumulated 73.7% Pb and 71.3% Cd.