Response surface methodology and reaction optimization to product zero-valent iron nanoparticles for organic pollutant remediation

Abstract

Abstract Zero-valent metals such as Al0, Zn0, Ti0, and Fe0 with well explored catalytic activity have gained wide spread applications in the remediation proposes. Due to extremely high surface to volume ratio, nanoscale zero-valent metals showed increased catalytic potential and introduced as promising catalysts. Among zero-valent metal nanoparticles, zero-valent iron nanoparticles (ZVINPs) are one of the most employed nanostructures in remediation studies. These particles are effective Fenton-like catalysts and employed to remove organic contaminations. Recent studies indicated that plant mediated synthesized ZVINPs are more efficient in this regard than chemically synthesized nanoparticles. The extract of green tea is extensively used for green synthesis of various metallic nanoparticles and iron based nanoparticles. In the present work, design of experiments (DoE) and response surface methodology (RSM) was applied to find out effective reaction parameters and optimal reaction condition for maximum production of ZVINPs by using green tea extract. For this purpose, at first, a fractional factorial design was used to screen the reaction parameters (reaction time, temperature, amount of leaf extract, and metal precursor concentration) in the synthesis process. Subsequently, the central composite face (CCF) design was utilized for reaction optimization. Amount of green tea extract and iron precursor concentration were found to be the most effective parameters. In a regular 10 mL reaction, maximum productivity was achieved by employing 9 mL tea extract and 25 mM (final concentration) ferric chloride. The prepared nanoparticles were identified to be amorphous ZVINPs with a low magnetization value of 80 memu/g. The particles diameter was measured to be 5–20 nm with 11.2 nm mean size. The particles pose effective catalytic activity for organic contaminants removal. Methyl orange was tested as a common model compound and particles were capable to eliminate more than 50% of the initial dye in just 2 h.