The Application of Biogenically Created Sorbent for Metal Ions Elimination

The aim of this work was to study the sorption ability of biogenic iron sulphides created by sulphate-reducing bacteria (SRB). They were isolated using growth media Postgate C, at 30°C, under anaerobic conditions from mineral spring Gajdovka (Košice). Biogenic sorbent precipitates were synthesized in sulphides form in reagent bottles with SRB culture and modified nutrient medium during 10 months in semicontinuous cultivation mode. The mode consisted of several phases, when fresh medium was added to the bottles in order to support the bacterial growth and precipitates creation. Abiotic controls of samples were performed in same conditions, but without bacteria. At the end of cultivation, the generated samples were separated from suspensions by centrifugation, dried, analysed (EDX, SEM, XRD) and used for sorption experiments. EDX results confirmed the presence of iron and sulphur as a major part of biogenic preci - pitates. Abiotic (non-biogenic) samples consisted of iron phosphate. SEM analysis revealed non-smooth particles and aggregates up to tens of micrometers. XRD showed mainly amorphous or poorly crystalline precipitates. Non-biogenic precipitates were identified as mineral vivianit. Sorption of zinc and cadmium from model solutions was realized by prepared sorbent samples in 100 ml Erlenmeyer flasks, with sorbent dose 1g/l, during 24 hours. The concentrations of metal ions were determined by AAS. Sorption process was most remarkable during initial 30 minutes. The metals cations from model solutions with low initial concentration (10 and 20 mg/l) were adsorbed well and the equilibrium was attained very quickly. Sorbent showed better affinity for cadmium than for zinc.