Lakshmi Prasanna Lingamdinne

Preparation and characterization of porous reduced graphene oxide based inverse spinel nickel ferrite nanocomposite for adsorption removal of radionuclides

For the removal of uranium(VI) (U(VI)) and thorium(IV) (Th(IV)), graphene oxide based inverse spinel nickel ferrite (GONF) nanocomposite and reduced graphene oxide based inverse spinel nickel ferrite (rGONF) nanocomposite were prepared by co-precipitation of GO with nickel and iron salts in one pot. The spectral characterization analyses revealed that GONF and rGONF have a porous surface morphology with an average particle size of 41.41nm and 32.16nm, respectively. The magnetic property measurement system (MPMS) studies confirmed the formation of ferromagnetic GONF and superparamagnetic rGONF. The adsorption kinetics studies found that the pseudo-second-order kinetics was well tune to the U(VI) and Th(IV) adsorption. The results of adsorption isotherms showed that the adsorption of U(VI) and Th(IV) were due to the monolayer on homogeneous surface of the GONF and rGONF. The adsorptions of both U(VI) and Th(IV) were increased with increasing system temperature from 293 to 333±2K. The thermodynamic studies reveal that the U(VI) and Th(IV) adsorption onto GONF and rGONF was endothermic. GONF and rGONF, which could be separated by external magnetic field, were recycled and re-used for up to five cycles without any significant loss of adsorption capacity.

Mechanism and comparison of needle-type non-thermal direct and indirect atmospheric pressure plasma jets on the degradation of dyes

Purified water supply for human use, agriculture and industry is the major global priority nowadays. The advanced oxidation process based on atmospheric pressure non-thermal plasma (NTP) has been used for purification of wastewater, although the underlying mechanisms of degradation of organic pollutants are still unknown. In this study we employ two needle-type atmospheric pressure non-thermal plasma jets, i.e., indirect (ID-APPJ) and direct (D-APPJ) jets operating at Ar feed gas, for the treatment of methylene blue, methyl orange and congo red dyes, for two different times (i.e., 20 min and 30 min). Specifically, we study the decolorization/degradation of all three dyes using the above mentioned plasma sources, by means of UV-Vis spectroscopy, HPLC and a density meter. We also employ mass spectroscopy to verify whether only decolorization or also degradation takes place after treatment of the dyes by the NTP jets. Additionally, we analyze the interaction of OH radicals with all three dyes using reactive molecular dynamics simulations, based on the density functional-tight binding method. This investigation represents the first report on the degradation of these three different dyes by two types of NTP setups, analyzed by various methods, and based on both experimental and computational studies.

Porous graphene oxide based inverse spinel nickel ferrite nanocomposites for the enhanced adsorption removal of arsenic

Porous graphene oxide based magnetic inverse spinel nickel ferrite nanocomposites, namely graphene oxide based inverse spinel nickel ferrite (GONF) and reduced graphene oxide based inverse spinel nickel ferrite (rGONF), with particle sizes of around 30 to 40 nm were prepared by the co-precipitation of graphene oxide (GO) with nickel and iron salts in one pot. GONF and rGONF, having ferromagnetic and superparamagnetic properties respectively, were separated easily within 10 seconds, using a small external magnetic field. These nanocomposites were used for the adsorption removal of As(III) and As(V). Compared to bare nickel ferrite, other nanocomposites and GO, the nanocomposites show a high adsorption capacity for As(III) and As(V), with considerable enhancement. The enhanced high adsorption capacity is due to the increased number of pores and adsorption sites with increasing surface area in the GONF and rGONF composites, through reducing the aggregation of bare ferrites. The adsorption results found that more than 99.9% arsenic removal was achieved with the present nanocomposites. Since the nanocomposites show good stability without loss of their adsorption capacity for up to 5 cycles, they can be used for the practical removal of arsenic from water.

Effective adsorptive removal of 2,4,6-trinitrotoluene and hexahydro-1,3,5-trinitro-1,3,5-triazine by pseudographitic carbon: kinetics, equilibrium and thermodynamics

Environmental context Explosive organic compounds such as 2,4,6-trinitrotoluene (TNT) and hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) are major constituents of ammunition materials. These compounds are of environmental concern because they can have a significant impact on ecosystems and humans. Through investigations of adsorption kinetics, isotherms and thermodynamics, we demonstrate the suitability of pseudographitic carbon for removing TNT and RDX from groundwater, and additionally confirm the viability of the use of pseudographitic carbon through comparison with other adsorbents. Abstract 2,4,6-Trinitrotoluene (TNT) and hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) – common explosives in military munitions – can easily enter groundwater supplies and have an adverse impact on human health. There is great concern about the need to remove these explosives from groundwater, and this study presents pseudographitic carbon (PGC) prepared from edible sugar as a material to remove explosives from contaminated groundwater via adsorption. The purity and physicochemical characteristics of the PGC were characterised using advanced spectroscopic techniques. The adsorption mechanism and its efficiency were investigated in terms of the non-linear adsorption kinetics, isotherms and thermodynamics using TNT and RDX adsorption data. The results of the non-linear modelling indicate that TNT and RDX adsorption was determined by rate-limiting monolayer exothermic adsorption on the homogeneous PGC surface. Ionic strength was studied with various ions, and the results indicate that the adsorption of TNT and RDX was significantly influenced by divalent cations and the carbonate anion. The results of desorption and re-use tests indicate that acetone and acetonitrile are the best desorbing agents. The PGC can be recycled and re-used for up to 3 cycles, with insignificant loss in adsorption efficiency. Finally, the PGC was applied to real spiked groundwater to evaluate its applicability in the field in removing TNT and RDX. The overall results indicate that PGC is a cost-effective and efficient adsorbent that effectively removes the organic explosives from groundwater, thereby reducing risk to humans and the aqueous environment.