Desilication kinetics of calcined boron mud in molten sodium hydroxide media

Desilication kinetics of calcined boron mud(CBM) occurring in molten sodium hydroxide media was investigated. The effects of factors such as reaction temperature and Na OH-to-CBM mass ratio on silicon extraction efficiency were studied. The results show that silicon extraction efficiency increases with increasing the reaction time and Na OH-to-CBM mass ratio. There are two stages for the desilication process of the calcined boron mud. The overall desilication process follows the shrinking-core model, and the first and second stages of the process were determined to obey the shrinking-core model for surface chemical reaction and the diffusion through the product layer, respectively. The activation energies of the first and second stages were calculated to be 44.78 k J/mol and 15.94 k J/mol, respectively.

Efficient synthesis of forsterite via high-temperature thermochemical reactions from boron mud waste without briquetting

Forsterite is a highly demanded material in high-temperature industries due to its superior performance in elevated temperatures.This study proposes synthesizing high-quality forsterite via high-temperature thermochemical reactions using abundant boron mud waste.The new synthesis method capitalizes on the high reactivity of fine raw powder materials,enabling the reaction to reach completion at low temperatures rapidly.The chemical characteristics,microscopic morphology,and structure of synthe-sized samples are systematically studied using XRD and SEM.The results confirm that boron mud can be efficiently transformed into forsterite after 10 min of reactions at 1500℃.The synthesized products attain over 98.7%densification and contain more than 85.0%forsterite with well-developed grains.The activation energy of forsterite grain growth in the 1100-1500℃temperature range is 165.5 kJ/mol.This study provides a low-cost method for producing forsterite and an efficient and environmentally friendly solution for treating solid waste.

Effect of Boron Mud and CaF_2 on Surface Tension and Density of CaO-SiO_2-B_2O_3 Ternary Slag Systems

The effect of boron mud and CaF2,which were used as fluxing agents,on surface tension and density of CaO-SiO2-B2O3 ternary slag systems was investigated.The surface tension and density were measured by using the ring detachment method and Archimedean method,respectively.The results indicated that surface tension and density of the slag systems decreased with increasing temperature in the range of 1380-1480℃.When 5%-10% CaF2 was employed as fluxing agent,the surface tension and density of slag were decreased with increasing CaF2 content,and the surface tension changed from 0.3to 0.6N/m,while the density changed from 3.4to 4.1g/cm3.However,when using 5%-10%boron mud as fluxing agent,the surface tension was enhanced,whereas the density decreased with the increase of boron mud content,and the variation range was 0.4-0.6N/m for surface tension and 3.2-3.9g/cm3 for the density.As a conclusion,using boron mud as fluxing agent to substitute for CaF2 did not cause significant changes in slag surface tension and density.

Extracting B_2O_3 from calcined boron mud using molten sodium hydroxide

Extracting B2O3 from calcined boron mud(CBM) was studied. The effect of factors such as reaction temperature and NaO H-to-CBM mass ratio on B2O3 extraction efficiency was investigated. The results show that increasing reaction temperature and NaO H-to-CBM mass ratio increases B2O3 extraction efficiency. There are two stages for the B2O3 extracting process: 0–20 min is the first stage, which is rapid; 20–50 min is the second stage, which is slower than the first stage. The overall extracting process follows the shrinking core model, and the first and second stages are determined to obey the surface chemical reaction model and the diffusion through the products layer model,respectively. The activation energies of the first and second stages are calculated to be 41.74 and 15.43 kJ·mol-1,respectively. The B2O3 extracting kinetics equations of the first and second stages are also obtained.

Recovery of silica from sodium silicate solution of calcined boron mud

The effect of several parameters on the recovery of silicon dioxide from calcined boron mud（CBM）such as stirring speed, temperature, sodium silicate concentration, and carbonation time was studied. The recovery of silicon dioxide is 88 % when the stirring speed is450 r min-1, temperature is 60 °C, sodium silicate concentration is 1 mol L-1, and the carbonation time is 6 h.The effect of carbonation time on the recovery of silicon dioxide is divided into three kinetic regimes, and the carbonation process of sodium silicate solution follows a second-order reaction based on the double-film theory model. The apparent rate constant of the three kinetic regimes is 0.064, 3.178, and 1.130 L h mol-1, respectively.The amorphous SiO_2 products obtained by carbonating the purified solution have 99.6 % purity and are spherical with diameters of about 100 nm.