Synthesis of green and ecofriendly iron nanoparticles using plant part extracts: application on the removal of phosphorus from aqueous media

Abstract

In recent years, the iron nanoparticles whose production with the help of green approaches demonstrated great potential as an alternative to the costly and environmentally toxic chemical nanoparticles have received considerable attention. The nanoscale particles of zero-valent iron, green-synthesized by green tea (GFe-n) and walnut green hull (WFe-n) extract, were used to adsorb phosphorus from the aqueous solution. The TEM, SEM, FT-IR, XRD, and DLS results indicated that the nanoscale iron particles were successfully prepared. The zeta potential measurements showed that the pH values of the point of zero charge (pHpzc) of GFe-n and WFe-n were about 7.50 and 8.10, respectively. The variables whose influence on phosphorus adsorption was systematically studied included adsorbent dosage, initial concentration, ionic strength, coexisting anions, contact time, and pH. The investigation of phosphorus adsorption showed that the rate of adsorption was high in the pH range varying from 2 to 5, while a decrease was observed in the level of adsorption when pH further increased in the experimental suspensions. The results indicated that the efficiency of phosphorus removal enhanced as the dosage of GFe-n and WFe-n rose from 2 to 20 mg L−1. The isotherm data were well fitted with the Langmuir equation, and the values for qmax were 53.47 and 45.82 mg g−1 for GFe-n and WFe-n, respectively. Concerning the kinetic data, the results indicated a reasonable fit of the pseudo-second-order model to the data, suggesting that the rate-limiting step for phosphorus removal might be chemisorption process. The results demonstrated that the Fe nanoparticles synthesized by the plant part extracts could suitably remove phosphorus from water and wastewater.