Preparation of Granulated Biomass Carbon Catalysts—Structure Tailoring, Characterization, and Use in Catalytic Wet Air Oxidation of Bisphenol A

Riikka Juhola,Tao Hu,Ulla Lassi,Davide Bergna,Sari Tuomikoski,Mika Huuhtanen,Anne Heponiemi

doi:10.3390/catal11020251

Abstract

New carbonized biomass–metakaolin (PSD/MK_Fe) granular composite catalyst materials were manufactured for the catalytic wet air oxidation (CWAO) of bisphenol A (BPA). These catalysts were characterized using different analytical and spectroscopic techniques, and results showed that the catalysts’ final properties were influenced by the addition of metakaolin (MK), polyvinyl alcohol, boric acid, and iron. Under the optimal CWAO experimental conditions (p: 20 bar, T: 160 °C, initial pH: 5–6, c[catalyst]: 1.0 g/L), nearly complete BPA conversion (>98%) and total organic carbon (TOC) conversion of 70% were reached. A key factor behind the enhanced catalytic activity was high specific surface area, although catalytic activity was also affected by surface acidity. These results confirmed the high efficiency of the current BPA conversion process involving the use of the easily separable and reusable PSD/MK_Fe catalyst. Therefore, biomass composite catalysts can be regarded as efficient catalysts for the oxidation of BPA during the CWAO process.

Highlights

Catalytic wet air oxidation (CWAO) is one of the most economical and environmentally friendly wastewater treatment technologies used to break down organic matters into a more biodegradable form
The specific surface area (SSA) remained relatively high, and no major differences in SSA were observed between the composite granules (AC/MK and activated carbon (AC)/MK_Fe vs. PSD/MK and PSD/MK_Fe)
The evolution of the pH of zero-point charge (pHzpc) values throughout the material modification process can be clearly seen; the nature of both the main raw materials (AC0 and PSD0) changed gradually from highly basic to highly acidic, indicating that possible acidic functionalities were incorporated onto the surface of the catalyst materials

Summary

Introduction

Catalytic wet air oxidation (CWAO) is one of the most economical and environmentally friendly wastewater treatment technologies used to break down organic matters into a more biodegradable form. The CWAO process can be efficiently conducted under mild operating conditions (low temperature and pressure) owing to the performance of heterogeneous catalysts [4,5,6]. In finding new catalytic materials with high activity and stability, various heterogeneous catalysts (e.g., noble metals, metal oxides, and carbon materials) have been prepared and tested for the CWAO of model compounds and real wastewater [5,7]. During the CWAO of organic compounds, heterogeneous catalysts are deactivated by metal leaching and by carbonaceous deposits on their surface [3,8].

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