Adsorption of the malachite green dye of macadamia husk-activated carbon prepared using a household pyrolysis kiln

Activated carbon has found its key applications in the adsorption of polluted industrial dyes in water. In this work, macadamia husk biochar (MHC) was prepared using a household pyrolysis kiln before being activated with phosphoric acid (H3PO4) to obtain macadamia husk-activated carbon MHAC. A preliminary study was made on the two activation conditions of MHC: H3PO4 (w/v); 1: 1 and 1: 3 for the removal of malachite green (MG) dye. Experimental results analysis disclosed that the adsorption process was highly controlled by time of contact, MHAC particle size, MHAC dosage and initial dye concentration. With the use of the MHAC particle size of 125-202 m, MHAC dosage of 6 g.L−1and 120 and min contact time, the removal efficiency reached >99% at the MG concentration of 40 ppm before being degraded to around 75% at 70-80 ppm MG. Impregnation with Zn(NO3)2.6H2O on the MHAC surface could maintain the removal efficiency to >99% in all initial dye concentrations (40-80 ppm) so the maximum removal capacity was increased to ∼130 mg.g−1.