Removal of copper ions from aqueous solution using NaOH-treated rice husk

The present study investigates the removal of copper ions (Cu (II)) from aqueous solution using chemically treated rice husk (TRH). The chemical treatment was carried out using NaOH solution and the effect of contact time (t(c)), adsorbent dosage (D-ad), initial Cu (II) concentration ([Cu](i)), and temperature (T) on the percentage removals of Cu (II) (%R-Cu) were investigated. Different analytical techniques (FTIR, SEM, and EDX) were used to confirm the adsorption (ads) of Cu (II) onto the TRH. Theadskinetics was tested against pseudo-first-order (PFO) and pseudo-second-order (PSO) models as well as Langmuir and Freundlich isotherms. Treating RH with NaOH altered the surface and functional groups, and on the surface of RH, the ionic ligands with high electro-attraction to Cu increased and thus improved the removal efficiency. The %R(Cu)decreased by increasing the [Cu](i)and increased by increasing thec(t),D-ad, andT. Up to 97% Cu removal was achieved inc(t)of 30 min usingD(ad)of 0.3 g [Cu](i)of 25 mg L(-1)andT= 280 K. Theadsof Cu on TRH is endothermic, spontaneous, follows Langmuir isotherms, and exhibited a PSO kinetics. Moreover, the TRH was successfully regenerated and used for further adsorption cycles using 1 M HNO3.