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Effective transportation of fly ash–water slurry through a pipeline from its generation site, a power plant, to a storage site by replacing commercial surfactants such as cetyl trimethyl ammonium bromide and sodium dodecyl sulfate by a natural dispersant extracted from Sapindus laurifolia was studied. The stability of fly ash slurry was determined from its rheological parameters, dispersant concentration, and stabilization mechanism. From surface tensiometric data, the critical micelle concentration of the dispersant was obtained to be 0.017 g/cc. The stabilization of high-concentration fly ash slurry has been studied through its rheological behavior by variation of temperature and dispersant and ash concentration. The rheological result obtained for fly ash concentrations in the range of 50–65% slurry was best justified by the Bingham plastic model. The wettability of fly ash particles is increased in the presence of dispersants, which is inferred from reduction of the surface tension value. The stabilization mechanism of the slurry is explained by a steric factor as indicated by the decrease in the zeta potential value. Air pollution is minimized at its destination site due to agglomeration of fly ash particles, which is confirmed from the SEM microphotograph.

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A B S T R A C TBioremediation is a low-cost eco-friendly separation technique for the treatment of pollutants such as heavy metals and organics from wastewaters. In the present study, a biosorbent, Lonicera japonica flowers powder (LJFP) was prepared from Lonicera japonica flowers (LJF) for treating Pb (II) and Co(II) from aqueous solutions and was well characterized by FT-IR and SEM-EDX. The kinetic results showed that the kinetics of both metal ions was rate limiting pseudo-second order. However, Pb(II) was also involved in chemisorptions, which was proved by the Elovich kinetic model. The equilibrium data of Pb(II) were tuned with Langmuir isotherm whereas Co (II) was fit to Freundlich isotherm model. The maximum uptake capacities of LJFP for Pb(II) and Co(II) were 19.61 and 43.48 mg/g at 298 ± 2 K, pH 6.0. Thermodynamic studies were conducted in the range of temperature, 298-313 ± 2 K, and were revealed that the sorption process of Pb(II) and Co(II) on LJFP was endothermic. Overall studies demonstrated that the biomass, LJFP is a promising, efficient, economical, and reusable sorbent.

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Nickel metal hydride (NiMH) batteries are extensively used in the manufacturing of portable electronic devices as well as electric vehicles due to their specific properties including high energy density, precise volume, resistance to overcharge, etc. These NiMH batteries contain significant amounts of rare earth metals (REMs) along with Co and Ni which are discarded due to illegal dumping and improper recycling practices. In view of their strategic, economic, and industrial importance, and to mitigate the demand and supply gap of REMs and the limited availability of natural resources, it is necessary to explore secondary resources of REMs. Therefore, the present paper reports a feasible hydrometallurgical process flowsheet for the recovery of REMs and valuable metals from spent NiMH batteries. More than 90% dissolution of REMs (Nd, Ce and La) was achieved using 2 M H2SO4 at 75 °C in 60 min in the presence of 10% H2O2 (v/v). From the obtained leach liquor, the REMs, such as Nd and Ce, were recovered using 10% PC88A diluted in kerosene at eq. pH 1.5 and O/A ratio 1/1 in two stages of counter current extraction. La of 99% purity was selectively precipitated from the leach liquor in the pH range of 1.5 to 2.0, leaving Cu, Ni and Co in the filtrate. Further, Cu and Ni were extracted with LIX 84 at equilibrium pH 2.5 and 5, leaving Co in the raffinate. The developed process flow sheet is feasible and has potential for industrial exploitation after scale-up/pilot trails.