The commercial sulfate process for pigment production uses concentrated sulfuric acid(N 85 wt% H_2SO_4) as feeding material and discharges 8–10 tons of spend dilute acid(20 wt% H_2SO_4) per ton of product. Re-using s...The commercial sulfate process for pigment production uses concentrated sulfuric acid(N 85 wt% H_2SO_4) as feeding material and discharges 8–10 tons of spend dilute acid(20 wt% H_2SO_4) per ton of product. Re-using spend acid to leach ilmenite can cut the waste emission and save fresh feeding acid. However, the leaching reaction with dilute acid is very slow and the digestion efficiency is fairly low. This paper describes a wet-milling process to enhance the dilute-acid leaching of ilmenite that makes it possible to produce TiO_2 pigment in a more environmentally benign routine. The leaching kinetic study of unmilled ilmenite, dry milled 60 min ilmenite and wet milled 60 min ilmenite was conducted by revision of the shrinking core model(SCM), incorporation of particle size distribution(PSD) into SCM. The results revealed that mechano-chemical activation method significantly increased the leaching efficiency of titanium from 36% to 76% by reducing the particle size and increasing the reaction contact area. On the other hand, the milling process increased the lattice deformation and amorphization of crystalline, which lowered the activation energies in the leaching process. Compared with dry milling operation, wet milling is more effective, the particle size distribution of wet-milled ilmenite was much narrower, smaller, and more uniform. Wet milling of ilmenite makes the leaching reaction with dilute acid(60 wt% H_2 SO_4) practicable and the re-use of spend acid becomes possible and economical.展开更多
Titania(TiO2) photocatalyst coatings have been fabricated by the low-cost approach of sulfuric-acid-bath pretreatment(SAP)followed soaked in sulfuric acid(SA) at room temperature then oxidated in air. The influence of...Titania(TiO2) photocatalyst coatings have been fabricated by the low-cost approach of sulfuric-acid-bath pretreatment(SAP)followed soaked in sulfuric acid(SA) at room temperature then oxidated in air. The influence of the SAP and soaked conditions on the surface morphology and photocatalytic activity of TiO2 on Ti coatings was investigated. With different SAP conditions,the surface morphologies of the TiO2 on Ti coatings clearly show the formed porous-like structure. With higher SA concentration,the porous-like structure becomes obviously. With extending soaked time,the porous-like structure tends to disappear. Raman spectroscopy reveals that the formed TiO2 coatings are with mixed-phase of anatase and rutile. Compared with those of SA concentration and SAP time,the influence of the soaked time on the phase transformation is obvious. Notably,the photocatalytic activity of TiO2 on Ti coatings had been efficiently enhanced by extending the soaked time,compared with those of higher SA concentration and longer SAP time. The enhanced photocatalytic activity of TiO2 on Ti coatings could be related with the changed surface morphology,mixed-phase of anatase and rutile,and formed hydroxyl groups.展开更多
基金Supported by the National Natural Science Foundation of China(21236004)
文摘The commercial sulfate process for pigment production uses concentrated sulfuric acid(N 85 wt% H_2SO_4) as feeding material and discharges 8–10 tons of spend dilute acid(20 wt% H_2SO_4) per ton of product. Re-using spend acid to leach ilmenite can cut the waste emission and save fresh feeding acid. However, the leaching reaction with dilute acid is very slow and the digestion efficiency is fairly low. This paper describes a wet-milling process to enhance the dilute-acid leaching of ilmenite that makes it possible to produce TiO_2 pigment in a more environmentally benign routine. The leaching kinetic study of unmilled ilmenite, dry milled 60 min ilmenite and wet milled 60 min ilmenite was conducted by revision of the shrinking core model(SCM), incorporation of particle size distribution(PSD) into SCM. The results revealed that mechano-chemical activation method significantly increased the leaching efficiency of titanium from 36% to 76% by reducing the particle size and increasing the reaction contact area. On the other hand, the milling process increased the lattice deformation and amorphization of crystalline, which lowered the activation energies in the leaching process. Compared with dry milling operation, wet milling is more effective, the particle size distribution of wet-milled ilmenite was much narrower, smaller, and more uniform. Wet milling of ilmenite makes the leaching reaction with dilute acid(60 wt% H_2 SO_4) practicable and the re-use of spend acid becomes possible and economical.
文摘Titania(TiO2) photocatalyst coatings have been fabricated by the low-cost approach of sulfuric-acid-bath pretreatment(SAP)followed soaked in sulfuric acid(SA) at room temperature then oxidated in air. The influence of the SAP and soaked conditions on the surface morphology and photocatalytic activity of TiO2 on Ti coatings was investigated. With different SAP conditions,the surface morphologies of the TiO2 on Ti coatings clearly show the formed porous-like structure. With higher SA concentration,the porous-like structure becomes obviously. With extending soaked time,the porous-like structure tends to disappear. Raman spectroscopy reveals that the formed TiO2 coatings are with mixed-phase of anatase and rutile. Compared with those of SA concentration and SAP time,the influence of the soaked time on the phase transformation is obvious. Notably,the photocatalytic activity of TiO2 on Ti coatings had been efficiently enhanced by extending the soaked time,compared with those of higher SA concentration and longer SAP time. The enhanced photocatalytic activity of TiO2 on Ti coatings could be related with the changed surface morphology,mixed-phase of anatase and rutile,and formed hydroxyl groups.
