Activated Carbon from Sewage Sludge for Preconcentration of Copper

Sewage sludge was pyrolyzed in an inert atmosphere at 550 degrees C after chemical treatment with ZnCl2 or KOH using an organic precursor to inorganic weight ratio of 1:1. The materials were used as adsorbents for removal of Cu(II) from aqueous solution. The adsorbents were characterized using adsorption/desorption nitrogen isotherms, thermal analysis, scanning electron microscopy, and elemental analysis. The results showed that copper removal was linked to surface pH and compounds present on the surface of the adsorbent. The KOH-treated adsorbent had a smaller surface area (186m(2) g(-1)) than the ZnCl2-treated adsorbent (192m(2) g(-1)). However, the KOH-treated adsorbent provided more efficient removal of Cu(II). The performance of the KOH-treated adsorbent may be due to the presence of basic groups on the surface. The Liu isotherm model provided the best description of the equilibrium data: The maximum adsorption capacities at 298K for KOH-treated, ZnCl2-treated, and untreated sewage sludge were 31.85, 19.79, and 3.513mgg(-1), respectively. The highest desorption was obtained using 1.50molL(-1) of HNO3 as the eluent. The recoveries of Cu(II) loaded adsorbents were 98.9% for ZnCl2-treated and 95.5% for KOH-treated adsorbents.