Stem powder and its active carbon of Arachis hypogaea plant for lead (II) removal: application to treat battery-based industrial effluents.

Stem powder and its active carbon of Arachis hypogaea plant are identified to have strong adsorptivity for lead ions. The bio-sorbents are characterized by conventional methods including XRD and FTIR analysis. These biomaterials are investigated for their maximum adsorption for lead ions by optimizing the extraction conditions. The maximum removal is observed in the pH range of 6-7 for both sorbents. With stem powders, the removal is 76.0% from a simulated lead solution of concentration: 20.0 mg/L with 1.5 g/L of the sorbent and at an equilibration time of 2.0 h. With the active carbon, the maximum extraction of: 86.0% is observed at pH: 6.5 with 1.0 g/L of the sorbent after an equilibration time of 1.5 h. The sorption capacities are 32.0 mg/g for stem powders, and 40.5 mg/g for active carbon. Many co-ions have marginal interference. Spent adsorbents can be recycled after regeneration. Thermodynamic investigations reveal the spontaneity and endothermic nature of adsorption. High ΔH values viz., 26.45 kJ/mole for AHSP and 46.40 kJ/mole for AHSAC, confirm the bonding of Pb2+ ions with the sorbents is either "ion-exchange" and/or a sort of "complex formation." The disorder at the solid and liquid boundary is indicated by high positive ΔS values and it is a favorable condition for good Pb2+ adsorption. On analysis of different kinetic and isotherm models, the sorption of Pb2+ ions follows Pseudo-2nd order and Langmuir models. This confirms the mono-layer adsorption of Pb2+ ions on the humongous surface of the sorbent. The adsorbents are successfully applied to treat industrial effluent samples.

In the present investigation, stem powder and its active carbon of Arachis hypogaea plant are identified to have strong adsorptivity for highly toxic lead ions. Successful methodologies are developed for the maximum extraction of lead ions from industrial wastewater at a convenient nearly neutral pH. The adsorption capacities are as high as: 32.0 mg/g for stem powders and 40.5 mg/g for active carbon. The sorbents are characterized and the sorption mechanism is investigated. The novelty of the present investigation is that highly toxic lead ions can be easily removed from polluted water by using simple bio-adsorbents by adopting convenient procedures.

Synthesis of nanoZrO2 via simple new green routes and its effective application as adsorbent in phosphate remediation of water with or without immobilization in Al-alginate beads.

Nano particles of ZrO2 of average size 10.91 nm are successfully synthesized via green routes from a solvent blend of water and ethylene glycol (4:1 v/v). Bio-extract of seeds of Sapindus plant is employed as stabilizing and/or capping agent and homogeneous method of precipitation is adopted to generate the precipitating agent. The nZrO2 particles are immobilized in aluminum alginate beads (nZrO2-Al- alig). Nano-ZrO2 and beads are investigated as adsorbents for the extraction of phosphate from water. The controlling physicochemical parameters are studied for the maximum phosphate removal using simulate water. The optimum conditions are: pH: 7; sorbent dosage: 0.1 g/100 mL for nZrO2 and 0.08 g/100 mL for beads; equilibration time: 30 min.for nZrO2 and 35 min for beads; initial phosphate concentration: 50 mg/L; temperature: 30 ± 1 °C; 300 rpm. The adsorption capacities are: 126.2 mg/g for nZrO2 and 173.0 mg/g for 'nZrO2-Al- alig' and they are higher than many reported in literature. The beads, besides facilitating the easy filtration, are exhibiting enhanced cumulative phosphate-adsorption nature of nanoZrO2 and Al-alginate. X-ray diffraction (XRD), Fourier transform infrared (FTIR), field emission scanning electron microscopy (FESEM) and energy-dispersive X-ray (EDX) investigations are employed in characterizing the adsorbents. Of the various isotherm models analyzed to assess the nature of adsorption, Freundlich model provides the best correlation (R2 = 0.99 for nZrO2 and R2 = 0.99 for 'nZrO2-Al-alig'), indicating the heterogeneous and multi-layered adsorption process. Thermodynamic studies reveal the endothermic and spontaneous nature of sorption. Pseudo-second-order model of kinetics describes the adsorption well. Spent adsorbents can be regenerated with marginal loss of adsorption capacity until five cycles. The sorbents are successfully applied to remove phosphate from polluted lake water samples.