Formation and Phase Transformation of MgCO(3)·3H(2)O Whiskers in the Presence of Sodium Dodecyl Sulfate

[Image: see text] Huge amounts of MgCl(2)·6H(2)O are produced annually as a byproduct or waste from KCl production in the Qinghai province of China. An ecological and economic way to solve this problem is transforming the abandoned MgCl(2)·6H(2)O to valuable MgCO(3)·3H(2)O whiskers. The formation and phase transformation of MgCO(3)·3H(2)O whiskers were studied in the crystallization process, in which MgCl(2) and NH(4)HCO(3) were precipitated in the presence of sodium dodecyl sulfate (SDS) at 50 °C. Results showed that porous spherical MgCO(3)·3H(2)O, MgCO(3)·3H(2)O whiskers, and flocculent rod-like 4MgCO(3)·Mg(OH)(2)·4H(2)O were formed with decreasing concentration of SDS as the crystallization proceeded. When the concentration of SDS was lower than the critical micellar concentration (6.5 mmol·L(–1)) at 60 min, SDS was beneficial for the growth in the [010] direction to form one-dimensional MgCO(3)·3H(2)O whiskers with a high aspect ratio, good uniformity, and a smooth surface (length, 60–70 μm; aspect ratio, 110–140).