Synthesis and Characterization of Carbon and Carbon-Nitrogen Doped Black TiO2 Nanomaterials and Their Application in Sonophotocatalytic Remediation of Treated Agro-Industrial Wastewater

Saifur Rahman; Rab Nawaz; Javed Akbar Khan; Habib Ullah; Muhammad Irfan; Adam Glowacz; Katarzyna Lyp-Wronska; Lukasz Wzorek; Mohammad Kamal Asif Khan; Mohammed Jalalah; Mabkhoot A Alsaiari; Abdulkarem H Almawgani

doi:10.3390/ma14206175

Synthesis and Characterization of Carbon and Carbon-Nitrogen Doped Black TiO₂ Nanomaterials and Their Application in Sonophotocatalytic Remediation of Treated Agro-Industrial Wastewater

Materials (Basel). 2021 Oct 18;14(20):6175. doi: 10.3390/ma14206175.

Authors

Affiliations

¹ Electrical Engineering Department, College of Engineering, Najran University Saudi Arabia, Najran 61441, Saudi Arabia.
² Fundamental and Applied Sciences (FASD), Universiti Teknologi PETRONAS (UTP), Seri Iskandar 32610, Malaysia.
³ Centre of Innovative Nanostructures and Nanodevices (COINN), Institute of Autonomous System, Universiti Teknologi PETRONAS (UTP), Seri Iskandar 32610, Malaysia.
⁴ Mechanical Engineering Department, Universiti Teknologi Petronas, Seri Iskandar 32610, Malaysia.
⁵ Department of Automatic Control and Robotics, Faculty of Electrical Engineering, Automatics, Computer Science and Biomedical Engineering, AGH University of Science and Technology, al. A. Mickiewicza 30, 30-059 Kraków, Poland.
⁶ Department of Materials Science and Non-Ferrous Metal Engineering, Faculty of Non-Ferrous Metals, AGH University of Science and Technology, al. Mickiewicza 30, 30-059 Kraków, Poland.
⁷ Wzorek.Systems, ul. Kapelanka 10/18, 30-347 Kraków, Poland.
⁸ Mechanical Engineering Department, College of Engineering, Najran University Saudi Arabia, Najran 11001, Saudi Arabia.
⁹ Empty Qaurter Research Unit, Chemistry Department, College of Science and Art at Sharurah, Najran University Saudi Arabia, Najran 61441, Saudi Arabia.

Abstract

The conventional open ponding system employed for palm oil mill agro-effluent (POME) treatment fails to lower the levels of organic pollutants to the mandatory standard discharge limits. In this work, carbon doped black TiO₂ (CB-TiO₂) and carbon-nitrogen co-doped black TiO₂ (CNB-TiO₂) were synthesized via glycerol assisted sol-gel techniques and employed for the remediation of treated palm oil mill effluent (TPOME). Both the samples were anatase phase, with a crystallite size of 11.09-22.18 nm, lower bandgap of 2.06-2.63 eV, superior visible light absorption ability, and a high surface area of 239.99-347.26 m²/g. The performance of CNB-TiO₂ was higher (51.48%) compared to only (45.72%) CB-TiO₂. Thus, the CNB-TiO₂ is employed in sonophotocatalytic reactions. Sonophotocatalytic process based on CNB-TiO₂, assisted by hydrogen peroxide (H₂O₂), and operated at an ultrasonication (US) frequency of 30 kHz and 40 W power under visible light irradiation proved to be the most efficient for chemical oxygen demand (COD) removal. More than 90% of COD was removed within 60 min of sonophotocatalytic reaction, producing the effluent with the COD concentration well below the stipulated permissible limit of 50 mg/L. The electrical energy required per order of magnitude was estimated to be only 177.59 kWh/m³, indicating extreme viability of the proposed process for the remediation of TPOME.

Keywords: agro-industrial wastewater; bandgap; carbon-nitrogen doped TiO2; chemical oxygen demand; electrical energy consumption; remediation; sonophotocatalysis; visible light absorption.