Removal of Cd²⁺, Pb²⁺, and Zn²⁺ from contaminated water using dolomite powder

ABSTRACT

Dolomite collected from Surat Thani Province in Thailand was investigated for use as a sorbent for the removal of divalent heavy metal cations from an aqueous solution. The sorbent had a surface area of 2.46 m²/g and a pH of zero point charge (pHzpc) of 9.2. Batch sorption was used to examine the effect of the pH (pH 3–7) on the sorption capacity of Cd²⁺, Pb²⁺ and Zn²⁺, alone or together as an equimolar mixture at various concentrations. Alone, each heavy metal cation was adsorbed faster at a higher pH, where the sorption of Cd²⁺ and Pb²⁺ fitted a Langmuir isotherm, but Zn²⁺ sorption best fitted a Freundlich isotherm. Under equimolar competitive sorption, the sorption capacity of each cation was decreased by 75.8% (0.29–0.07 mM/g), 82.8% (0.53–0.09 mM/g), and 95.7% (0.84–0.04 mM/g) for Cd²⁺, Pb²⁺ and Zn²⁺, respectively, compared to that with the respective single cation. Desorption of these heavy metal cations from dolomite was low, with an average desorption level of 0.06–17.4%. Furthermore, since dolomite is readily available and rather cheap, it is potentially suitable for use as an efficient sorbent to sorb Cd²⁺ and Pb²⁺, and perhaps Zn²⁺, from contaminated water.

KEYWORDS:

• dolomite
• competitive sorption
• heavy metals
• pH
• Thailand

Funding

The authors thankfully acknowledge the support of the Center of Excellence on Hazardous Substance Management (HSM) and the International Postgraduate Program in Environmental Management, Graduate School, Chulalongkorn University, Ratchadaphiseksomphot Endowment Fund, the Grant for International Research Integration Chula Research Scholar, Ratchadaphiseksomphot Endowment Fund (GCURS-59–06-79–01), the Office of Higher Education Commission (OHEC) and the S&T Postgraduate Education and Research Development Office (PERDO) for financial support of the research program. The authors thank the Ratchadaphiseksomphot Endowment Fund, Chulalongkorn University for the Research Unit (RU-Site Rem).