Process Optimization for the Production of Activated Carbon from Waste Coconut Shells in Trinidad & Tobago

Abstract

Produced water that is generated from the local oil and gas industry is associated with disposal challenges due to the presence of the pollutant phenol in excess of statutory discharge limits. As Trinidad & Tobago (TT) moves towards achieving sustainable development goals of waste minimization and pollution reduction, produced water treatment and reuse, as well as the indiscriminate disposal of waste coconut shells, are receiving national attention due to adverse environmental impacts. In developing countries, activated carbon (AC) made from cheap and abundantly available coconut shells has been successfully used to remove phenol from water by utilizing a packed bed adsorber. The adoption of the packed bed adsorber technology requires critical technical data on the phenol adsorption capacity of the AC manufactured from the waste coconut shells. Moreover, manufacturing AC involves firstly, carbonizing the coconut shells firstly, and then activating them using an oxidizing agent such as carbon dioxide (CO­₂). The objectives of this study were to optimize the carbonization and activation process conditions for the manufacturing of AC from waste coconut shells. The optimized carbonization and activation process conditions were found to be 600°C for 90 mins, and 900°C for 10 mins using a CO­₂ flowrate of 0.8 L min^-1. A maximum phenol adsorption capacity of 0.013 mg g^-1 corresponding to 76% phenol removal at 25°C was obtained. A Brunauer-Emmett-Teller (BET) surface area of 452.9 m² g^-1 and an average pore size of 1.79 nm was obtained for the optimized sample, with micropores accounting for 91% of the total pore volume. This study shows that the environmentally hazardous and indiscriminately disposed waste coconut shells in TT can be converted to AC to be utilized in a packed bed adsorber for water treatment. This waste minimization strategy supports the socio-economic transformation plan outlined in TT’s Vision 2030 National Development Strategy.