Fabrication of iron nanoparticles using Leptolyngbya valderiana and investigation of its Cr (VI) removal potential in the free and biomass associated forms

This study reported the ability of L. valderiana to fabricate iron nano particles of definite shape and size, as well as the enhanced effectiveness of the synthesized nanoparticle loaded biomass in removal of hexavalent chromium [Cr (VI)] from aqueous solution compared to free iron nano particles. Spindle-shaped nano scale zerovalent irons were synthesized by live biomass at intracellular and extracellular levels with the dimensions of 47.42 ± 3.86 × 7.7 ± 2.01 nm and 66.37 ± 3.09 × 12.49 ± 4.01 nm, respectively. The nanosorbents were prepared separately from intracellular particles (NI), extracellular particles (NE) and nano‑iron loaded biomass (BN). All the adsorbents were tested for chromium removal from Cr (VI) aqueous solutions with concentrations in the range of 5–20 mg L−1. The adsorption parameters were optimized. The removal rate and adsorption capacity, i.e., Langmuir constant (KL) of nano‑iron loaded biomass (BN) toward Cr (VI) reached the peak at 0.0439 L mg−1 of adsorbent, followed by intracellular particles (NI) (0.0162 L mg−1 of adsorbent) and extracellular particles (NE) (0.009 L mg−1 of adsorbent). The adsorption kinetics data of nano‑iron loaded biomass (BN) fitted well with the pseudo-second-order kinetic model and Freundlich isotherm model whereas, the other two nanosorbent-assisted removal processes followed the pseudo-first-order kinetic model and Langmuir isotherm model. Moreover, nano‑iron loaded biomass (BN) was the easiest to handle and showed maximum adsorption capacity; therefore, portraying it as a low-cost, environmentally benign potential nanosorbent for the removal of Cr (VI) from industrial waste.