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.

Novel adsorbents for the removal of toxic cadmium ions from polluted water.

Cadmium is one of the most toxic heavy metal ions found in wastewaters and its remedial methods are globally investigated. Removal methods based on biomaterials as adsorbents are proving to be simple, effective and eco-friendly. In the present investigation, bio-adsorbents derived from Cochlospermum regium plant stems (CRSP) and its active carbon (CRAC) are observed to have good adsorption for toxic cadmium ions. Hence, extraction conditions are optimized for maximum Cd-extraction: 55.0% with 'CRSP' and 70.0% with 'CRAC', from Cd2+ solutions of concentration: 25.0 mg/L. The adsorption capacities are 6.9 mg/g with CRSP and 12.6 mg/g with 'CRAC'. When 'CRAC' is impregnated with nano-CeO2 (CRAC.nCeO2) and is used as adsorbent, the percentage of Cd-extraction is increased to 90.0% and adsorption capacity to 22.5 mg/g at the optimized extraction conditions. To overcome the agglomeration of nanoparticles, the 'CRAC.nCeO2' is immobilized in Zr-alginate beads and thus obtained beads are investigated as adsorbent. With beads (CRAC.nCeO2-Zr.alg), the percentage of Cd-adsorption is enhanced to 95.0% and adsorption capacity to 24.6 mg/g. The adsorbents are characterized by adopting XRD and FTIR techniques. The adsorption mechanism is assessed by evaluating thermodynamic parameters, isotherm and kinetic models. The thermodynamic parameters and FTIR spectral characteristics indicate the formation of 'surface complex' between Cd2+ and adsorbent's functional groups. The adsorption follows Freundlich isotherm and pseudo-second order model. Many co-ions have not effected the percentage of extraction and interestingly, the presence of some cations (Al3+ and Fe3+) have synergistically enhanced the Cd-extraction. Spent sorbents can be regenerated and reused with marginal loss of adsorption capacity. The adsorbents developed are successfully used to treat real Cd-polluted wastewater. The novelty of the present investigation is that the effective, eco-friendly, renewable and robust sorbents with high sorption capacities are developed for Cd-remediation of water.

The merit of the present investigation is that adsorbents with high sorption capacities, are developed based on bio materials of Cochlospermum regium and nano-CeO₂. Zirconium alginate beads doped with nano-CeO₂ and active carbon of Cochlospermum regium stems, are found to be highly effective for Cd-removal and spent adsorbent can be regenerated and re-used for five cycles.