Synthesis of Analcime Crystals and Simultaneous Potassium Extraction from Natrolite Syenite

Abstract

Analcime single crystals were successfully synthesized from natrolite syenite powder (K2O 10.89%) and 92.6% of potassium was extracted simultaneously by means of soda roasting followed by alkali-hydrothermal method. Effects of NaOH concentration, reaction temperature, and holding period on the analcime formation and potassium extraction were investigated systemically. The results indicated that NaOH concentration plays an important role in determining the chemical composition of zeolites and size distribution; by turning the NaOH concentrations, three different pure zeolites (i.e., the phillipsite-Na, the analcime, and the sodalite) were prepared. Besides, a higher temperature could accelerate the dissolution of K+ions and enhance the crystallinity degree of zeolite. The reactions involved in the analcime synthesis can be summarized as follows: sodium aluminum silicate dissolution→precipitation and dissolution of metastable zeolite-P→analcime nucleation→analcime growth. The extraction ratio of K+is associated with the types of synthesized zeolites, among which analcime is the most effective to promote potassium leaching out from zeolite lattice position. The optimal condition for analcime crystallization and K+leaching is found to be as follows: 175°C for 4 h in 0.5 mol/L NaOH solution.

Effect of Temperature and Concentration of Zeolite Catalysts from Geothermal Solid Waste in Biodiesel Production from Used Cooking Oil by Esterification–Transesterification Process

“…Based on the XRF analysis results in Table 3, the Si/Al ratio obtained is 2.39. This result is in accordance with the study conducted by Chen et al [28] who obtained the Si/Al ratio of 2.0.…”

Alkali-Hydrothermal Treatment of K-Rich Igneous Rocks for Their Direct Use as Potassic Fertilizers

“…However, despite other zeolites having been identified in low amounts by XRD, no clear characteristic morphology of these crystals has been observed in SEM. Some studies already proved that K-feldspar (microcline) forms other phases (well-crystallized zeolite) when hydrothermally treated using NaOH as an additive with various concentrations at high temperatures [35,69]. Chen et al (2017) and Liu et al (2019) used natrolite syenite and potassic syenite mainly composed of microcline, biotite, natrolite, muscovite and microcline, plagioclase, quartz, respectively [35,69].…”

“…Some studies already proved that K-feldspar (microcline) forms other phases (well-crystallized zeolite) when hydrothermally treated using NaOH as an additive with various concentrations at high temperatures [35,69]. Chen et al (2017) and Liu et al (2019) used natrolite syenite and potassic syenite mainly composed of microcline, biotite, natrolite, muscovite and microcline, plagioclase, quartz, respectively [35,69]. Although their mineralogy was close to our trachyte and syenite composition, zeolites were not well observed probably due to the low concentration of NaOH and the low temperature under which the treatments were carried out.…”

Síntesis hidrotermal de zeolitas a partir de ceniza volcánica mediante tratamiento alcalino y su potencial aplicación en la remoción de NH4+, Pb2+, Zn2+ y Mn2+

“…al., [21] confirman alta cristalización de zeolita NaP1 en pruebas de síntesis a una temperatura de 100ºC durante 22 horas. A una temperatura de 125°C se forma analcima (An) [22], la cantidad de zeolita NaP1 se reduce y la fase vítrea comienza a disolverse.…”