| dc.description.abstract | Over the past decade, cassava production has been accelerated, ranking as the 5th most produced food crop at an estimated global production of 298.8 million metric tons by 2020 as per the Food and Agriculture Organization (FAO). With the 10-20% peel composition of the tuber weight, the implied cassava peel production ranges between 29.88 to 59.76 million metric tons. The main application of cassava peels is Papering animal feeds. However, this is limited due to the peels’ low protein content (<6%). Throughout the past decade, cassava peels have been valorized into activated carbons with qualities able to curb recalcitrant adsorbates like heavy metals, dyes, and arsenics. However, the application of cassava peel-based activated carbon in the adsorption of pharmaceuticals from wastewater has not been explicitly studied. This study aimed at modifying the valorization processes of cassava peels into activated carbon capable of removing active pharmaceutical ingredients from wastewater. This involved, (i) characterization of peels of six predominant cassava varieties (NAROCAS 1, NAROCAS 2, NASE 1, NASE 3, NASE 14, and NASE 19) grown in Uganda for production of activated carbon (ii) optimization of activated carbon production conditions from the most viable peel variety, (iii) characterization of the wastewater from effluents of pharmaceutical manufacturing plants (PMPs) and wastewater treatment plants (WWTPs) in Kampala for active pharmaceutical ingredients (APIs), and (iv) determination of the performance of the produced activated carbon towards the removal of active pharmaceutical ingredients from wastewater.
All the six cassava peel varieties were potential activated carbon AC precursors with ash contents as low as <5% dry basis and fixed carbon of 13.78–15.34%. NAROCAS 1 cassava peel variety was the most suitable due to its lowest ash content (1.93%), high elemental carbon content (59.40%), balanced volatile matter (81.93%), and fixed carbon content (13.78%). Pre-leaching of the peels using 1– 4% NaOH revealed a more remarkable effect on the increase of volatile matter and fixed carbon (1.00% and 3.56% respectively) than ash content reduction (0.51%). The optimal process conditions for the production of physically activated carbon were found to be a temperature of 782 °C and a heating time of 148 mins resulting in a specific surface area of 756.42 m2g-1, and a yield of 4.57%. The best chemically activated carbon resulted from a 4.0%w/v NaOH pre-leaching at 50 °C and a 5:2 KOH: peel ratio of 5:2 (mass basis) activation at 60 °C for 3 hours. This was followed by carbonization at 780 °C for 2 hours resulting in a 42% yield, total pore volume of 0.756 cm3g-1, and the highest ever reported specific surface area for cassava peel activated carbon (CPAC) of 1684 m2g-1. The concentration ranges of the selected APIs targeted in this study were <LOD – 4.75, <LOD –1.37, <LOD – 1.17, and 0.28 – 19.55 for diclofenac, sulfamethoxazole, carbamazepine, and clarithromycin, respectively, in effluents of WWTPs whereas in treated wastewater from PMPs concentrations were <LOD, <LOD – 0.23, 5.30 – 7.4, <LOD – 0.14, and 0.12 – 4.53 mgL-1 for losartan, diclofenac, sulfamethoxazole, carbamazepine, and clarithromycin respectively. Through a batch experimental setup, the produced AC adsorbed 86.00, 58.00, and 68.50 % of carbamazepine (CBZ), clarithromycin (CLN), and trimethoprim (TRM) from effluent wastewater whereas from milli q water, 94.25, 73.50, and 84.5 % respectively were removed at an initial concentration of 20 mgL-1 for all the APIs and CPAC dosage of 2.0 gL-1. The maximum adsorption capacities attained were 1.487, 25.907, and 84.034 mgg-1 for CLN, TRM, and CBZ respectively exhibiting potential for CPAC to sequestrate APIs from water systems. The techno-economic analysis of a cassava peel-based AC manufacturing plant of 1 tonne/day capacity gave a 35% return on investment, a net present value of $ 648,331, and a Pay-back period of approximately 2 years. This study presents for the first time, the application of cassava peel-activated carbon in the treatment of wastewater with active pharmaceutical ingredients as the main target contaminants. | en_US |
