Adsorption applications of unmodified geothermal silica

•Unmodified geothermal silica is being used as a chromatographic material.•The process requires no additional chemicals.•A natural protein, phycocyanin, was extracted from blue-green algae.•A protein purity level (absorbance ratio 620nm/280nm) of 2.0 was obtained.•A byproduct of geothermal power plants is being utilized. Silica, precipitated out of geothermal fluid discharged from a geothermal powerplant in Svartsengi on the Reykjanes peninsula in Iceland, was used as a chromatographic adsorbent to extract blue colored protein, C-phycocyanin, from coccoid blue-green algae. The only supplement used was salt obtained by evaporating the geothermal fluid. Analysis of the silica, using scanning electron microscopy, X-ray diffractometry and Brunauer–Emmett–Teller (BET) adsorption confirmed it has a high specific surface area and is amorphous. Upon adsorption and subsequent elution the purity of the extracted protein, measured as the ratio of the light absorbance of 620 and 280nm, increased from 0.5 to above 2.0. Our results could facilitate utilization of a mostly unused byproduct of geothermal powerplants as chromatographic material.