Thermodynamic characterization and nucleation kinetics of boric acid: Process optimization for high-purity flaky boric acid with regulated particle size--颗粒学报PARTICUOLOGY

Thermodynamic characterization and nucleation kinetics of boric acid: Process optimization for high-purity flaky boric acid with regulated particle size

Xin Liu^{a d}, Xu Zhao^{a e}, Chunlai Yang^{a b c}, Xingwu Zou^{a b c *}, Fayan Zhu^{a c}

a Qinghai Institute of Salt Lakes, Chinese Academy of Sciences, Xining, Qinghai, 810008, China
b Qinghai Engineering and Technology Research Center of Comprehensive Utilization of Salt Lake Resources, Xining, 810008, China
c Key Laboratory of Green and High-end Utilization of Salt Lake Resources, Qinghai Institute of Salt Lakes, Chinese Academy of Sciences, Xining, 810008, China
d Chinese Academy of Sciences, Salt Lake Chemical Analysis & Test Center, Qinghai Salt Lake Research Institute, Xining, 810008, China
e School of Mechanical Engineering, Qinghai University, China

10.1016/j.partic.2026.06.034

Volume 117, October 2026, Pages 29-40

Received 20 April 2026, Revised 23 June 2026, Accepted 27 June 2026, Available online 15 July 2026, Version of Record 22 July 2026.

E-mail: zouxingwu@isl.ac.cn

Highlights

• Measured boric acid solubility at 293.15–333.15 K and calculated ΔH_d = 20.44 kJ mol⁻¹ and ΔS_d = 127.83 J mol⁻¹ K⁻¹.

• Quantified effects of mixing, cooling rate and initial mass ratio on boric acid metastable zone width.

• Revealed boric acid nucleation shift from progressive to instantaneous as temperature rises.

• Regulated boric acid crystal planes via modifier: inhibits (0 1 1)/(0 1 0) growth, promotes (4 -2 1) oriented growth.

• Optimized industrial preparation of high-purity flaky boric acid: 99.93% purity, >60% yield, 495 μm median size.

Abstract

To realize the controlled preparation of high-purity boric acid with regular morphology and uniform particle size, the thermodynamics and nucleation kinetics of boric acid in aqueous solution were systematically studied via an online turbidity system, and the preparation process was optimized. The solubility curve of boric acid at 293.15-333.15 K was plotted, and its dissolution thermodynamic parameters were calculated as the dissolution enthalpy is 20.44 kJ per mole, and the dissolution entropy is 127.83 J per mole per kelvin. The effects of stirring rate, cooling rate and initial mass fraction on the metastable zone width were clarified, and the nucleation mechanism was found to transform from gradual to instantaneous with increasing temperature. By introducing disodium ethylenediaminetetraacetate as a crystal growth modifier for selective crystal plane regulation, the optimal preparation process of high-purity flaky boric acid was obtained, with a product yield over 60% and a median particle size of 495 μm (200-1000 μm). This process successfully inhibits the growth of (0 1 1) and (0 1 0) crystal planes and promotes the oriented growth of (4 -2 1) crystal plane, forming regular flaky boric acid crystals. The research results enrich the theoretical system of boric acid crystallization and provide a reliable technical scheme for the industrial production of high-purity flaky boric acid.

Graphical abstract

Keywords

H₃BO₃; Solubility; Metastable zone width; Crystallization kinetics; Nucleation mechanism; High-purity preparation

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