Biosorption behavior and mechanism of beryllium from aqueous solution by aerobic granule

The treatment of Be-contaminated wastewater has been paid little attention, although beryllium (Be) and its compounds are of high toxicity. In this research, aerobic granule was for the first time introduced to remove Be from aqueous solution. Influencing factors including reaction time, initial Be concentration, pH, biosorbent dosage, and coexistent metal ions (Cd, Cu, and Fe) were investigated in batch experiments. The aerobic granule, characterized by element analysis and CLSM, was abundant in carboxyl, phosphoryl, amine and hydroxyl groups. Potentiometric titration experiment demonstrated that the pH effect on biosorption depended on the surface charge of granule (pHzpc = 2.4) and the species of Be (Be2+, Be(OH)+, and Be(OH)2) in solution. The coexistent metal ions would either inhibit Be uptake through competitive biosorption or promote Be uptake via coprecipitation, depending on the Ksp of coexistent metals. Kinetic and isotherm modeling studies revealed that the experiment data could be well described by pseudo-second-order model and Langmuir isotherm, respectively. The maximum biosorption capacity obtained in this experiment was 14.0 mg/g. The sequential extraction test and XPS analysis suggested that precipitation and ion exchange were the dominant mechanisms under the experimental conditions, and FTIR analysis revealed that functional groups like carboxyl and hydroxyl played an important role in the biosorption of Be.

• The biosorption of Be onto aerobic granule follows pseudo-second-order kinetics and Langmuir isotherm.
• The uptake of Be increases when the pH goes up.
• Precipitation and ion exchange are the dominant mechanisms.
• Carboxyl, hydroxyl and phosphoryl groups are involved in the biosorption of Be.