Enhancing of Copper (II) Adsorption Efficiency by Mixing Plantain and Orange Peelings as Bio-Sorbent Support

The present study focuses on the valorization of plantain and orange peels in the field of water treatment contaminated by heavy metals, especially copper (II). To carry out this study, simplex centroid mixture design was used to determine best mixture from plantain and orange peelings through iodine number, specific surface area and point of zero charge. The influence of contact time, adsorbed amount, bio-sorbent mass, medium temperature and medium pH were equally investigated from best mixture and thermodynamic parameters were also carried out. The results show that R², Absolute Average Deviation (AAD), biais factor and exactitude factor are respectively 89.39%, 0.01, 1.00 and 1.00 for iodine number, 94.13%, 0.03, 0.99 and 0.99 for Specific surface Area (SA) and 97.05%, 0.01, 1.00 and 1.00 for Point of Zero Charge (PZC). These values are in agreement with the interval set to validate the model. Besides, desirability is 1.00, 0.80 and 0.77 respectively for specific surface area, iodine number and zero point of charge and closer to 1. The best mixture from this study is 90% of orange peelings proportion and 10% of plantain peelings proportion. The results also show that contact time is 10 min, adsorbed amount of copper ions (II) increases with initial copper concentration, bio-sorbent mass and medium temperature. Adsorbed amount increases for pH between 3 and 5 and decreases for pH greater than 5. The efficiency of Copper (II) removal is about 88.11% for the native bio-sorbent and 97.04% for activated bio-sorbent. These efficiencies are higher than those obtained from orange and plantain peelings taken individually and are ranged between 70 and 85%. The pseudo second order describes perfectly the adsorption mechanism followed by intra particular diffusion while the isotherm adsorption is well described by Langmuir and Freundlich model. The thermodynamic parameters indicate that adsorption reaction is spontaneous, reversible and endothermic.