Preparation of Magnetic Activated Carbons from Cassava Peel using H3PO4 and KOH Activation by Microwave Heating for Naphthol Blue-Black Adsorption.

To address the separation problems and produce the reusable adsorbent, cassava peel magnetic activated carbon (MAC) prepared via microwave-assisted activation has been proposed to replace activated carbon (AC) for naphthol blue-black removal. To create MACs, ACs were embedded with nano-sized magnetite particles using co-precipitation methods. In this sense, 2 different activating agents (i.e., H3PO4 and KOH) have been used. H3PO4 activation provides a larger pore size and more functional groups, while KOH activation provides a larger surface area and higher porosity. The increase of H3PO4 concentration from 40 to 60 % leads to an increase in porosity as well as an increase in the weight ratio of KOH to char from 1 to 3. Impregnation magnetite to the ACs reduces surface area from 457.76 to 337.94 m² g-1 for KOH activation, and from 360.65 to 232.74 m² g-1 for H3PO4 activation, decreasing adsorption capacity from 97.5 to 97 % for KOH activation and from 99 to 98 % for H3PO4 activation. However, the adsorbent is easy to separate under the magnetic influence. The adsorption data of MAC by H3PO4 activation show suitability with the Redlich-Peterson isotherm model, suggesting that naphthol blue-black removal is not ideal monolayer adsorption, but a combination of physisorption and chemisorption processes that exhibit heterogeneity of naphthol blue-black adsorption on the surface of adsorbent. Meanwhile, for MAC by KOH activation, the Langmuir isotherm is more suitable. [ABSTRACT FROM AUTHOR]