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

doi:10.3390/ma14206175

Saifur Rahman, Mohammed Jalalah + Show 10 more

Open Access

https://doi.org/10.3390/ma14206175

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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.

Highlights

Palm oil production is a multistage process that generates an enormous amount of wastewater, commonly termed as palm oil mill effluent (POME)
The present study aims to synthesize carbon doped and carbon-nitrogen co-doped black TiO2 nanomaterials which can be activated by visible light, and investigate their performance in the advanced application of photocatalytic and sonophotocatalytic remediation of treated palm oil mill effluent (TPOME)
TPOME sample was strategically collected from the release point of a final stabilization pond of the palm oil industry situated in Perak, Malaysia

Summary

Introduction

Palm oil production is a multistage process that generates an enormous amount of wastewater, commonly termed as palm oil mill effluent (POME). To maintain a clean and pleasant environment, the palm oil industries are obliged to treat POME to comply with the stipulated discharge limits of 20 mg/L and 50 mg/L for biological oxygen demand (BOD) and chemical oxygen demand (COD), respectively, set by the Department of Environment (DOE) Malaysia [2]. Palm oil industries employ biological treatment (open ponding system) consisting of aerobic and anaerobic biological processes for POME treatment. While these traditional methods can decrease the COD and BOD levels to some extent, the final discharge quality frequently fails to comply with the regulatory discharge limit [3,4]. The presence of harmful organic fractions in TPOME might cause irreversible damage to aquatic ecosystem and the chemical pollution, due to the emission of TPOME contaminated with inorganic and organic pollutants may endanger the aquatic biodiversity [5,6]

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