• Boaventura, Rar
• Mayer, Da
• Pozdniakova, Ta
• Mazur, Lp
• Vilar, Vjp

Abstract

In this study, the removal of zinc from galvanization wastewaters was performed in a fixed bed column packed with brown macro-algae Laminaria hyperborea, acting as a natural cation exchanger (resin). The rinse wastewater presents a zinc concentration between 9 and 22 mg/L, a high concentration of light metals (mainly Na and Ca), a high conductivity (0.5-1.5 mS/cm) and a low organic content (DOC = 7 -15 mg C/L). The zinc speciation diagram showed that approximately 80% of zinc is in the form of Zn2+ and congruent to 20% as ZnSO4, considering the effluent matrix. From all operational conditions tested for zinc uptake (17 < bed height <27 cm, 4.5 < flow rate < 18.2 BV/h, 0.8 < particle equivalent diameter < 2.0 mm), the highest useful capacity (7.1 mg Zn/g algae) was obtained for D/dp = 31, LID = 11, 9.1 BV/h, tau = 6.4 min, corresponding to a service capacity of 124 BV (endpoint of 2 mg Zn/L). Elution was faster and near to 100% effective using 10 BV of HCl (1 M, 3.0%, 363 g HCl/L of resin), for flow rates higher than 4.5 BV/h. Calcium chloride solution (0.1 M) was selected as the best regenerant, allowing the reuse of the natural resin for more than 3 saturation/elution/regeneration cycles. The best operation conditions were scaled-up and tested in a pre-pilot plant. The scale-up design of the cation exchange process was proposed for the treatment of 2.4 m(3)/day of galvanization wastewater, resulting in an estimated reactants cost of 2.44 (sic)/m(3).

Topics

• impedance spectroscopy
• zinc
• mass spectrometry
• Calcium
• resin
• elution