Purification of Water from Manganese Compounds on a Modified Ceramic Membrane of Clay Minerals

Abstract

A high efficiency of the process of water purification from Mn(II) compounds formed at pH 8.3–8.4 on a Mn(II) modified microfiltration tubular ceramic membrane of clay materials, which was developed in the Dumansky Institute of Colloid Chemistry and Water Chemistry of the National Academy of Sciences of Ukraine, was shown. The conditions for the dynamic modification of the ceramic membrane with these compounds were determined. The effect of the initial Mn(II) concentration in a solution and its pH, the working pressure, the water purification time, and the additives of salts containing Cl–, $${\text{SO}}_{4}^{{2 - }}$$, $${\text{HCO}}_{3}^{ - }$$, and Са2+ions on the separation properties of the modified ceramic membrane was studied. The purification of water from Mn(II) compounds on the ceramic membrane was studied on the model MnCl2 ⋅ 4H2O salt solutions within a concentration range of 1.5–33.0 mg/dm3. It has been established that such a membrane can purify water from Mn(II) compounds to their maximum permissible concentration in drinking water at an initial manganese concentration of up to 4.34 mg/dm3, pHinit = 8.4, a working pressure of 1.0 MPa, and a purification time of 75–100 min, when a solution contains Cl–, $${\text{HCO}}_{3}^{ - }$$, $${\text{SO}}_{4}^{{2 - }}$$, and Ca2+ions, respectively, at a concentration of 200 mg/dm3 for each of the ions. The addition of salts containing the above ions to the initial solution at the moment when the maximum permissible concentration of manganese was attained had a slight effect on the ability of this ceramic membrane to retain the Mn(II) compounds. In this case, the specific productivity of the membrane was ranged within 0.16–0.20 m3/(m2 h). The obtained results might be explained by the steric membrane action mechanism based on the difference between the sizes of Mn(II) compound particles and membrane pores themselves with the further formation of an additional modifying layer of these particles on its surface.