Evaluation of activation parameters of activated carbon from coffee and cocoa seed husk rests: carbon yields and Ni(II) adsorption capacity study

Activated carbon produced by a traditional two-step activation procedure from coffee husks (HAC) and cocoa seed husks (CAC) were used as adsorbents for Ni(II) removal in aqueous solution. Temperature, activation time and added water amount used during the activation process are studied through a model equation designed by a two-level full factorial design. Analysis of variance was used in evaluating AC in multiple response optimization to maximize the yield and adsorption capacity as system responses. The adsorption behaviour of Ni(II) was also evaluated through isotherm models of Langmuir, Freundlich and Langmuir-Freundlich. For both CAC and HAC, the Langmuir-Freundlich model is slightly superior to the Langmuir and Freundlich models. Mostly CAC adsorbs higher amount of Ni(II) than HAC.