PVDF HFP_RuO2 Nanocomposite Aerogels Produced by Supercritical Drying for Electrochemical Oxidation of Model Tannery Wastewaters.

Maria Sarno,Lucia Baldino,Stefano Cardea,Carmela Scudieri,Ernesto Reverchon,Eleonora Ponticorvo

doi:10.3390/nano11061436

Abstract

A supercritical CO2 drying process was used to prepare an innovative nanocomposite, formed by a poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF HFP) aerogel loaded with RuO2 nanoparticles. The produced nanocomposites, at 10% and 60% w/w of RuO2, were tested for the electrochemical oxidation of model tannery wastewaters. The effect of the electrochemical oxidation parameters, like pH, temperature, and current density, on tannic acid, intermediates, and chemical oxygen demand (COD) removal, was investigated. In particular, the electrolysis of a simulated real tannery wastewater, using PVDF HFP_RuO2 60, was optimized working at pH 10, 40 °C, and setting the current density at 600 A/m2. Operating in this way, surfactants, sulfides, and tannins oxidation was achieved in about 2.5 h, ammonium nitrogen oxidation in 3 h, and COD removal in 5 h. When chloride-containing solutions were tested, the purification was due to indirect electrolysis, related to surface redox reactions generating active chlorine. Moreover, sulfide ions were converted into sulfates and ammonium nitrogen in gaseous N2.

Highlights

Electrochemical oxidation (EO) is an environmentally compatible technique that uses electrons to oxidize pollutants into carbon dioxide and water, or other oxides, without generating secondary pollutants [1,2]
PVDF HFP is characterized by a good electrochemical stability and affinity to polar liquid electrolytes [4,5,6]; whereas RuO2 is widely active in redox reactions [3,7,8,9]
Surfactants, sulfides, and tannins were oxidized in about 2.5 h, ammonium nitrogen in 3 h, and chemical oxygen demand (COD) was removed in 5 h

Summary

Introduction

Electrochemical oxidation (EO) is an environmentally compatible technique that uses electrons to oxidize pollutants into carbon dioxide and water, or other oxides, without generating secondary pollutants [1,2]. PVDF HFP is characterized by a good electrochemical stability and affinity to polar liquid electrolytes [4,5,6]; whereas RuO2 is widely active in redox reactions [3,7,8,9]. These properties, coupled with the possibility to potentiate the electrochemical oxidation activity using aerogels organized in a hierarchical structure from micro- to nanoscale [10], open perspectives for an industrial application of these nanocomposite systems.

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