Eco friendly adsorbents for removal of phenol from aqueous solution employing nanoparticle zero-valent iron synthesized from modified green tea bio-waste and supported on silty clay

The present research investigated a novel route for the synthesis of nanoparticle zero-valent iron (NZVI) utilizing an aqueous extract of green tea waste as a reductant with ferric chloride.Also,the supported nanoparticle zero-valent iron was synthesized using natural silty clay as a support material (SC-NZVI).The NZVI and SC-NZVI were characterized by infrared spectroscopy (FTIR),scanning electron microscope (SEM),X-ray diffraction (XRD),Brunauer-Emmett-Teller (BET),and zeta potential (ζ).The interpretation of the results demonstrated that the polyphenol and other antioxidants in green tea waste can be used as reduction and capping agents in NZVI syn-thesis,with silty clay an adequate support.Additionally,the experiments were carried out to explore phenol ad-sorption by NZVI and SC-NZVI.To determine the optimum conditions,the impact of diverse experimental factors(i.e.,initial pH,adsorbent dose,temperature,and concentration of phenol) was studied.Langmuir,Freundlich,and Tempkin isotherms were used as representatives of adsorption equilibrium.The obtained results indicated that the adsorption processes for both NZVI and SC-NZVI well fitted by the Freundlich isotherm model.The appropriateness of pseudo_first_order and pseudo_second_order kinetics was investigated.The experimental kinetics data were good explained by the second-order model.The thermodynamic parameters (△H0,△S0,and△G0) for NZVI and SC-NZVI were determined.The maximum removal rates of phenol at optimum conditions,when adsorbed onto NZVI and SC-NZVI,were found to be 94.8％ and 90.1％,respectively.