Lignin-Based, Surface-Deposited and embedded Nano Zero-Valent iron for P-Nitroaniline and P-Nitrophenol remediation

Abstract

Para nitroaniline (PNA) and para nitrophenol (PNP), used as pharmaceutical precursors, are highly carcinogenic and mutagenic priority pollutants. Nano zero-valent iron (nZVI) has garnered much recent attention as a remediation tool, owing to its advanced oxidation and adsorption capabilities. However, bare nZVI has inherent issues of agglomeration and passivation which can be mitigated using a support material like biochar (BC) known for its cost-effectiveness and eco-friendliness. Carbothermal reduction is a popular, relatively non-toxic approach for nZVI synthesis, forming highly stable nZVI. Allowing carbothermal reduction of iron on BC creates a surface-deposited material while allowing simultaneous pyrolysis and reduction of a mixture of iron and carbonaceous material to form an nZVI-embedded BC. There have been no previous studies done on organic contaminant removal by nZVI-embedded BC, nor have there been a comparative study between the two carbothermally synthesized materials. A comprehensive batch sorption study was carried out including pH, kinetic, isotherm, and regeneration experiments. Data indicates that the surface-deposited material shows higher adsorption capability while the embedded material exhibits superior regeneration ability. Thermodynamic data validate the spontaneity and feasibility across different temperatures. This study highlights the efficiency of BC-based nZVI as a potent tool for PNA and PNP remediation in aqueous systems.