Nickel removal by biosorption onto medlar male flowers coupled with photocatalysis on the spinel ZnMn(2)O(4)

Ni(2+) is a highly toxic above 0.07 mg/L and its removal is of high significance. The biosorption of Ni(2+) onto medlar male flowers (MMF) was studied in relation with the physical parameters like pH, contact time, biosorbent dosage, Ni(2+) concentration and temperature. The interaction biosorbent-Ni(2+) was examined by the FTIR technique. The equilibrium was achieved within 40 min and the data were well fitted by the Langmuir and Redlich-Peterson (R-P) models. The maximum Ni(2+) uptake capacity was 17.073 mg/g at 25°C and the Ni(2+) removal follows a pseudo-second order kinetic with activation energy of 13.3 kJ/mol. The thermodynamic parameters: ΔS°, ΔH° and ΔG° showed that the biosorption was spontaneous and endothermic. MMF was used as a post treatment technique and the biosorption was coupled with the visible light driven Ni(2+) reduction over the spinel ZnMn(2)O(4). The effect of the pH, ZnMn(2)O(4) loading and light intensity on the photoactivity was investigated. 77.5% of Ni(2+) was reduced after ~140 min under optimal conditions. The Ni(2+) removal reached a rate conversion of 96% of with the coupled system biosorption/photocatalysis is very promising for the water treatment.