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[Display omitted] • SAA can selectively control the surface properties of quartz. • Selective adsorption of SAA on quartz from quartz-magnesite mixtures. • Hydrogen bonding formed between the −N–H group of SAA and the oxygen atom of the O-Si-O group on quartz surface. Reverse flotation desiliconization from magnesite is significant for the exploitation of complex and barren magnesite resources. In this process, a critical issue is to find efficient and selective chemicals as flotation collectors. Herein, a cationic surfactant stearylamine acetate (SAA) was first used as a collector for the separation of magnesite and quartz. Micro-flotation experiments demonstrate that quartz can be separated from magnesite with a high Gaudin's selectivity index of 6.51 at slurry pH 5.0 and 70 mg/L SAA. Measurements of zeta potential and contact angle show that SAA selectively increased the surface charge and hydrophobicity of quartz. Field emission scanning electron microscopy (FESEM/EDS) and atomic force microscope (AFM) imaging indicate greater adsorption density of SAA on quartz than magnesite, with significantly higher nitrogen element content and RMS surface roughness of quartz. We also used surface-sensitive time of flight secondary ion mass spectrometry (TOF-SIMS) and FTIR spectroscopy to characterize the selective adsorption of SAA on quartz from quartz-magnesite mixtures. Apart from electrostatic attraction, it is found that the selective adsorption was attributed to hydrogen bonding formed between the −N–H group of SAA and the oxygen atom of the O-Si-O group on quartz surface. [ABSTRACT FROM AUTHOR]

This research investigated water leaching of roasted vanadium slag and studied the effects of leaching parameters, such as agitation speed, temperature, liquid-to-solid ratio, and leaching time. Further, solution purification via desiliconization and precipitation of ammonium vanadate were studied using the vanadium solution obtained from the water leaching of roasted vanadium slag. Vanadium solution contains residual silicon (1.67 g/L), which should be removed before ammonium vanadate precipitation. Based on the results, vanadium can be effectively recovered from vanadium slag and a recovery efficiency of 96.9% was obtained under optimal water leaching conditions. During solution purification, silicon can be precipitated with Al 2 (SO 4) 3 to very low levels without any significant vanadium loss. The ammonium vanadate precipitation achieved a high precipitation efficiency of >99%. • Roasted vanadium slag was water leached with the high (96.9%) vanadium yield • Solution has high vanadium content, but also silicon as impurity (1.67 g/L) • Silicon was successfully removed with Al 2 (SO 4) 3 without significant vanadium loss • Finally, ammonium vanadate was precipitated under optimal conditions • Recovery efficiency of 99% was achieved after 300 min of precipitation. [ABSTRACT FROM AUTHOR]

Abstract: The technology of hot metal pretreatment had tremendous improvements in past decades and was widely used by the overwhelming majority of steelworks in Japan. While, since the first hot metal pretreatment station was established in Taiyuan Iron and Steel Co., Ltd in the later period of 1980s, this process began to be applied in domestic steel plants. And now 30 years have passed, the desilionization and dephosphorization process are still rarely seldom used in China except desulphurization process in most carbon steel plants. So in this paper, the metallurgical principles and effects of hot metal desiliconization were analyzed in great details. Meanwhile, the optimum silicon content of hot metal between iron-making and steelmaking process was summarized and calculated. The necessity of hot metal desiliconizaiton was discussed for the iron and steel companies in China. [Copyright &y& Elsevier]

Ammonium hydrofluoride was used for fluorination of titanium-silica-containing raw materials (by the example of quartz-leucoxene concentrate of Yaregskoye deposit, South Timan, Russia). The optimum physical and chemical conditions for the processing of quartz-leucoxene concentrates, which allow obtaining a high‑titanium product containing >85% TiO 2 in a mixture of rutile and anatase at relatively low temperatures and a short processing time (300°С for 2 h), are presented. The results of thermodynamic calculations on interaction of NH 4 HF 2 with the components of the leucoxene concentrate were checked in experiments. The main phases formed during the interaction of NH 4 HF 2 with the two components of the leucoxene concentrate have been determined by thermal and X-ray phase analysis methods. The rate of fluorination depending on the amount of ammonium hydrofluoride and the influence of mechanical activation of mineral raw materials was studied. Optimal ratio is SiO 2 :NH 4 HF 2 = 1:4. Material grinding leads to its activation and intermediate products ((NH 4) 3 TiF 7 , (NH 4) 2 SiF 6)) are formed at lower temperatures. This will reduce the consumption of fluorinating component and allow to obtain a high‑titanium product with minimal costs. • Desiliconization of quartz-leucoxene concentrates using ammonium hydrofluoride (NH 4 HF 2) was done. • Based on thermodynamic calculations the stages of intermediate products formation in a multicomponent system were defined. • Desiliconization was carried out by simple thermal treatment at 300 °C. • High‑titanium concentrates containing >85% TiO 2 (a mixture of rutile and anatase) were obtained. [ABSTRACT FROM AUTHOR]

Abstract: The desiliconization reaction in sodium aluminate solution was studied by adding tricalcium hydroaluminate (C3AH6). C3AH6 prepared at 323 K has a relatively high desiliconization capacity. Kinetic results show that the desiliconization reaction is first-order in SiO2 concentration, and the apparent activation energy is estimated to be 96 kJ/mol between 363 and 393 K, which is lower than that from adding Ca(OH)2. During the desiliconization process, SiO2(OH)2 − ions enter the interior of C3AH6 particles and react with them further. As a result, the distribution of SiO2 in the desiliconization product (DSP) is more uniform than that from adding CaO. Also, the SiO2 content in DSP is higher. [Copyright &y& Elsevier]

Chromium sludge is a hazardous solid waste which cannot be effectively treated but only piled up and abandoned, causing serious environment pollution and resource wasting. This work proposes an effective novel process to separately recover all resources in chromium sludge via a sustainable way. The obtained acid solving liquid from chromium sludge is desiliconized by cationic flocculant (PCAM) to induce coprecipitation of polysilicate gel and PCAM, which mixture is calcinated to generate the product of white carbon black in purity of 94.35% with a recovery of 92.58%. After desiliconization, V in the solving liquid is selectively extracted by microemulsion (ME), which is recovered as V 2 O 5 in purity of 99.34% with a recovery of 95.53% by the subsequent procedure of stripping-precipitation-calcination. The Fe3+ in raffinate is reduced to Fe2+ cations by Na 2 SO 3 , and is then recovered by H 2 C 2 O 4 precipitation to generate the FeC 2 O 4 product in purity of 99.12% with a recovery of 98.25%. Cr3+ cations in residual solution are recovered by alkaline precipitation and calcination to generate the Cr 2 O 3 product in purity of 98.25% with a recovery of 92.68%. This work provides fresh penetrations into the synchronous detoxification, resource recovery and value-added utilization of hazardous industrial solid wastes. ga1 • Si from chromium sludge can be recovered as white carbon black in high purity of 94.35%. • 95.53% of V(V) and 92.68% of Cr(VI) in chromium sludge were recovered separately. • All the SiO 2 , V 2 O 5 FeC 2 O 4 and Cr 2 O 3 final products have high purity. • Efficient recovery of Si, V, Fe and Cr resources simultaneously treated the solid waste. [ABSTRACT FROM AUTHOR]

Hollow zeolite single crystals have received extensive attention due to their unique cavities and outstanding catalytic performance. Although many kinds of zeolites have been synthesized with hollow structures, the related synthesis of hollow SSZ-13 zeolites has not been reported yet. In this work, we first synthesized hollow zeolite SSZ-13 single crystals by a simple and economical strategy without additional templates, which involves adjusting the spatial chemistry distribution of elements throughout the crystals to create Al-zoned and forming cavity by selective desiliconization. Furthermore, we doped the synthesized hollow zeolite SSZ-13 with copper, and the hollow Cu-SSZ-13 zeolite exhibits an enhanced catalytic activity of selective catalytic reduction (SCR) of NO x with NH 3 compared with the traditional solid Cu-SSZ-13. Image 1 • Hollow SSZ-13 zeolites are synthesized by one-pot method. • Synthetic process involves creating Al-zoned and selective desiliconization. • The Al-zoned is created by adjusting the spatial distribution of Al elements in the crystal. • NH 3 -SCR activity of hollow Cu-SSZ-13 is better than conventional solid Cu-SSZ-13. [ABSTRACT FROM AUTHOR]