2. Experimental
2.1. Biosorbent preparation
Peanut shells were extensively washed in running tap water for
1–2 h to remove coloration and dirt, and then washed with distilled
water several times. The washed sorbent was transferred to an oven
set at 50 °C for 24 h to reduce the water content. The dried sorbent
was crushed and milled. The particle sizes were less than 30 μm.
2.2. Metal solution preparation
Solutions of Cu2+ and Cr3+ ions were prepared by dissolving
predefined amounts of CuSO4 and Cr(NO3)3, respectively, in distilled