Review of metal sulphide precipitation

Removal of arsenic (III) and arsenic (V) from aqueous medium using chitosan-coated biosorbent.

Treatment of acid mine water by use of heavy metal precipitation and ion exchange

Studies on cellulose acetate-polysulfone ultrafiltration membranes: II. Effect of additive concentration

Removal of copper(II) by adsorption onto peanut hull carbon from water and copper plating industry wastewater

Sulfide precipitation with Na2S is found to be highly effective to obtain a high degree of separation of heavy metal cations (Cd, Zn, Cu, and Pb) and of the oxyanions of arsenic and selenium from complex wastewaters. The metal separation characteristics are evaluated with a dilute synthetic mixture and with an actual copper smelting plant wastewater. The overall separation of arsenic and other heavy metals and precipitate settling rates are optimum at sulfide dosages about 60% of the theoretical values and at a final pH greater than 8.0. The removals of Cd, Zn, and Cu from the actual wastewaters are greater than 99%, and As and Se removals are 98 and >92%, respectively. Cd, Cu, and Zn concentrations in the range of 0.05 to 0.1 mg/1 can be achieved with sulfide precipitation. The metal separations and settling rates obtained with conventional hydroxide precipitation (lime) are considerably lower than those obtained with sulfide precipitation.

Separation of Toxic Heavy Metals by Sulfide Precipitation

Complex aqueous suspensions containing a nonionic surfactant, phosphates, silicate, hypochlorite, oil, and kaolinite particulates are subjected to continuous flow membrane ultrafiltration with noncellulosic membranes. The ultrafiltrate water flux and the rejections by the Millipore PSAL membrane of total organic carbon, surfactant, and total phosphate are related by stepwise, multiple linear regression analysis (logarithmic model) to transmembrane pressure difference, thin channel velocity, membrane resistance, and feed solution concentration. The variables are adjusted to eliminate gel polarization and to minimize concentration polarization.

The data are extended, by the development and use of a computer simulation scale-up procedure, to a 1 000 cm3/s (23 000 gal/day) laundry waste treatment and water recovery unit. The procedure considers banks of modules in series, banks in parallel, and a parallel-series-tapered arrangement. Membrane area requirements per unit ultrafiltrate water flux and solute rejections are predicted for water recoveries up to 95% of the inlet flow rate.

A. B. Jumawan

Papers

Separation of Toxic Heavy Metals by Sulfide Precipitation

Membrane ultrafiltration of a nonionic surfactant and inorganic salts from complex aqueous suspensions: Design for water reuse