Efficient Pb removal through the formations of (basic) carbonate precipitates from different sources during wet stirred ball milling with CaCO3

Calcium carbonate (CaCO3) may be used for lead removal. However, due to compact structure and high crystallinity of CaCO3, the utilization of CO32- is low and Pb removal only stays at the extent of physical adsorption and surface precipitation. In this research, a wet stirred ball milling process was introduced to induce nearly stoichiometric reactions between lead salts of nitrate, chloride or sulfate with CaCO3 by consequently updating fresh surfaces of CaCO3. The CaCO3 could completely dissolve in the system for the removal of Pb2+ on the same chemical molar equivalent. The removal rate reached simply over 99% with the aid of ball milling, based on the precipitations in the forms of lead carbonate (PbCO3) from soluble nitrate and basic lead carbonate (Pb-3(CO3)(2)(OH)(2)) from the hardly soluble sulfate occurring in a very wide concentration range. The process offered a new path for the treatment of abandoned lead paste based on the conversion of PbSO4 to PbCO3 or Pb-3(CO3)(2)(OH)(2) as well as recycling of lead resources from multi-metal coexisting lead-containing waste solutions. These (basic) carbonates precipitates may be used as secondary resources, while achieving environmental purification. (C) 2019 Elsevier B.V. All rights reserved.