Abstract: Aqueous basic polyaluminum-iron halide solutions, useful as coagulants in waste water treatment are disclosed. The polyaluminum-iron halide solution is prepared by reacting an aqueous polyaluminum halide solution with one or more members of the group consisting of ferrous halide and ferric halide resulting in a solution containing a concentration of metal ions ranging from about 1.35 to 4.5 mol/liter as a dissolved salt of the formulaAl.sub.1-x Fe.sub.x.sup.III Fe.sub.y.sup.II (OH).sub.3+2y-z Hal.sub.zwherein Hal is chlorine, bromine, iodine or mixtures thereof; (x+y)(1-x) is about 0.2 to 1.5; (3+2y-z)(3+2y) is about 0.24 to 0.67; and z is less than 3+2y wherein x/y is about 0 to 1. Alternatively, the coagulant solution is prepared by reacting an aqueous aluminum halide solution or low basic polyaluminum halide solution with iron. Preferably the halide employed is chloride.

Abstract: Aqueous basic polyaluminum-iron halide solutions, useful as coagulants in waste water treatment are disclosed. The polyaluminum-iron halide solution is prepared by reacting an aqueous polyaluminum halide solution with one or more members of the group consisting of ferrous halide and ferric halide resulting in a solution containing a concentration of metal ions ranging from about 1.35 to 4.5 mol/liter as a dissolved salt of the formulaAl.sub.1-x Fe.sub.x.sup.III Fe.sub.y.sup.II (OH).sub.3+2y-z Hal.sub.zwherein Hal is chlorine, bromine, iodine or mixtures thereof; (x+y)/(1-x) is about 0.2 to 1.5; 3+2y-z/3+2y is about 0.24 to 0.67; and z is less than 3+2y. Alternatively, the coagulant solution is prepared by reacting an aqueous aluminum halide solution or low basic polyaluminum halide solution with iron. Preferably the halide employed is chloride.

Abstract: Soda values from the crystallizer purge liquor from the process of making sodium carbonate from trona are recovered by cooling the purge liquor to temperature below about 32.degree. C. to effect crystallization of sodium carbonate decahydrate crystals therefrom, and recovering the decahydrate crystals. Optionally, the decahydrate crystals may be heated to convert them to sodium carbonate monohydrate crystals. Sensible heat of the crystallizer purge liquor and/or sensible heat and latent heat of vaporization of the sodium carbonate process crystallizer vapors may be recovered by using it to heat the sodium carbonate decahydrate crystals to convert them to sodium carbonate monohydrate crystals.