Effect of mechanical-chemical modification on adsorption of beryllium by calcite

The treatment of beryllium wastewater has become a major problem in industry. In this paper, CaCO₃ is creatively proposed to treat beryllium-containing wastewater. Calcite was modified by an omnidirectional planetary ball mill by a mechanical-chemical method. The results show that the maximum adsorption capacity of CaCO₃ for beryllium is up to 45 mg/g. The optimum treatment conditions were pH = 7 and the amount of adsorbent was 1 g/L, and the best removal rate was 99%. The concentration of beryllium in the CaCO₃-treated solution is less than 5 μg/L, which meets the international emission standard. The results show that the surface co-precipitation reaction between CaCO₃ and Be (II) mainly occurs. Two different precipitates are generated on the used-CaCO₃ surface; one is the tightly connected Be (OH)₂ precipitation, and the other is the loose Be₂(OH)₂CO₃ precipitation. When the pH of the solution exceeds 5.5, Be²⁺ in the solution is first precipitated by Be (OH)₂. After CaCO₃ is added, CO₃^2- will further react with Be₃(OH)₃³⁺ to form Be₂(OH)₂CO₃ precipitation. CaCO₃ can be considered as an adsorbent with great potential to remove beryllium from industrial wastewater.