Hydrothermal synthesis of mixtures of NaA zeolite and sodalite from Ti-bearing electric arc furnace slag

Abstract

Ti-bearing electric arc furnace slag (Ti-bearing EAF slag) is the main solid waste generated in the direct reduction iron making process. During the extraction process of Ti from Ti-bearing EAF slag, a byproduct containing abundant Si and Al was seldom utilized, thus leading to waste of valuable elements and secondary pollution. In this paper, NaA zeolite (6Na 2 O$6Al 2 O 3 $12SiO 2 ) and sodalite (SOD, 4Na 2 O$3Al 2 O 3 $6SiO 2 ) were synthesized successfully using the by-product as a precursor. The effects of the SiO 2 /Al 2 O 3 molar ratio (n(SiO 2 )/n(Al 2 O 3 )), H 2 O/Na 2 O molar ratio (n(H 2 O)/n(Na 2 O)), hydrothermal temperature and time on the crystal phase and microstructure of the prepared zeolites were systematically investigated. The results indicated that NaA zeolite with good crystallinity and cubic morphology was obtained at 140 C for 3 h with n(SiO 2 )/n(Al 2 O 3 ) and n(H 2 O)/n(Na 2 O) fixed at 2.0 : 1 and 100 : 1, respectively. Decreasing n(H 2 O)/n(Na 2 O), raising the hydrothermal temperature and prolonging the hydrothermal time were beneficial for the formation of spherical SOD zeolite. The phase transformation between NaA and SOD zeolite was discussed and a mechanism was proposed to explain the phenomenon of these zeolites coexisting in the obtained samples. In addition, the removal performances of Cu 2+ in aqueous solutions using zeolites synthesized at different temperatures were studied. The maximum removal capacity of the prepared zeolite can reach 1.346 mmol g À1 for 180 min.

One-Step Synthesis of Hydroxysodalite Using Natural Bentonite at Moderate Temperatures

“…As shown in Figure 10, a well-crystallized 4A zeolite was formed when the reaction temperature was 60 °C. With an increase of temperature, the intensity of the diffraction peaks of hydroxysodalite gradually increased, which agrees with a similar result reported by Li et al [27]. Increasing the temperature to 90 °C caused the diffraction peaks of 4A zeolite to vanish, leaving only the diffraction peaks of hydroxysodalite, suggesting that relatively pure hydroxysodalite was prepared at this temperature.…”

Ironmaking and Steelmaking Slags as Sustainable Adsorbents for Industrial Effluents and Wastewater Treatment: A Critical Review of Properties, Performance, Challenges and Opportunities

“…The photocatalytic activity increased with increasing Si/Al ratio. Due to the abundance of major constituent elements such Ti, Si and Al in slags, these studies clearly highlight novel approaches to the utilisation of otherwise problematic Ti-bearing steelmaking slags [134,135].…”

“…To date, several studies have reported on the benefits of modification and/or activation treatment to increase the specific surface area and density of adsorption sites on the surfaces of the adsorbent particles [42,57,[59][60][61][62][63][64][65][66]. Other studies have also proposed the synthesis of functionalised adsorbents such as geopolymers [74,[118][119][120][121][122][123], permeable reactive barriers or slag filters [124][125][126][127][128][129][130][131][132], zeolites and zeolite precursors [133][134][135] and layered double-hydroxide-based adsorbents [133][134][135][136][137][138]. This section discusses in detail the opportunities to improve the adsorption capacity of slag-based adsorbents.…”

“…Thus, the high silica, aluminosilicate and calcium-aluminosilicate content of ironmaking and steelmaking slags makes them ideal precursors for the synthesis of zeolites and their variants. To date, several studies have explored the synthesis of zeolites using ironmaking and steelmaking slags as precursors [133][134][135]. In particular, Sugano et al [133] However, the adsorption capacity for Cu 2+ ions by NaA synthesised at 120 • C was significantly higher (1.346 mmol g −1 ) than that of sodalite synthesised at 140 • C (0.722 mmol g −1 ) and 160 • C (0.673 mmol g −1 ).…”

Single‐step process without organic template for the formation of zeolite A from RHA

“…Terzano et al utilized municipal glass and aluminium solid wastes for the preparation of NaA zeolite . Ti‐bearing electric arc furnace slag was used for the preparation of NaA zeolite . Maia et al reported the use of industrial kaolin waste for the preparation of zeolite A .…”