Dissolution kinetics of aluminum and iron from coal mining waste by hydrochloric acid

The extrartion of aluminum from coal mining waste(CMW) is an important industrial process.The two major problems in applications are low aluminum dissolution efficiency and high iron content in the raw material,which affect the quantity and quality of products.To improve the aluminum recovery process,the leaching kinetics of CMW with hydrochloric acid was studied.A shrinking core model was used to investigate aluminum and iron dissolution kinetics.Based on the kinetic characteristics,a process for recovering aluminum was proposed and tested experimentally.It is found that the aluminum leaching reaction is controlled by surface reaction at low temperatures(40-80℃) and by diffusion process at higher temperatures(90-106℃).The iron dissolution process is dominated by surface reaction at 40-100℃.The results show that iron could be dissolved or separated by concentrated hydrochloric acid.Fine grinding will improve aluminum dissolution significantly.

Influence of Mechanical Activation on Acid Leaching Dephosphorization of High-phosphorus Iron Ore Concentrates

High pressure roll grinding（HPRG）and ball milling were compared to investigate the influence of mechanical activation on the acid leaching dephosphorization of a high-phosphorus iron ore concentrate,which was manufactured through magnetizing roasting-magnetic separation of high-phosphorus oolitic iron ores.The results indicated that when high-phosphorus iron ore concentrates containing 54.92 mass% iron and 0.76 mass% phosphorus were directly processed through acid leaching,iron ore concentrates containing 55.74mass%iron and 0.33mass%phosphorus with an iron recovery of 84.64%and dephosphorization of 63.79% were obtained.When high-phosphorus iron ore concentrates activated by ball milling were processed by acid leaching,iron ore concentrates containing56.03mass%iron and 0.21mass% phosphorus with an iron recovery of 85.65% and dephosphorization of 77.49%were obtained.Meanwhile,when high-phosphorus iron ore concentrates activated by HPRG were processed by acid leaching,iron ore concentrates containing 58.02mass%iron and 0.10mass% phosphorus were obtained,with the iron recovery reaching 88.42% and the dephosphorization rate reaching 88.99%.Mechanistic studies demonstrated that ball milling can reduce the particle size,demonstrating aprominent reunion phenomenon.In contrast,HPRG pretreatment contributes to the formation of more cracks within the particles and selective dissociation of iron and P bearing minerals,which can provide the favorable kinetic conditions to accelerate the solid-liquid reaction rate.As such,the crystal structure is destroyed and the surface energy of mineral particles is strengthened by mechanical activation,further strengthening the dephosphorization.

Identification of an Appropriate Formulation for Domestic Water Ceramic Filters from Soukamna Clay(Cameroon)

This paper deals with the formulation of ceramic filters having the porosity adapted to domestic potable water treatment.The filters were made from clays and rice husk obtained from the Far North region of Cameroon(Logone Valley).Nine formulations were investigated to choose those that might have the porosity standing between 35 and 50%(the ideal porosity adapted for water treatment).The nine formulations investigated were as follows:clay:rice husk mixture weight ratio 0.7:0.3;0.8:0.2 and 0.9:0.1 with the particle size of 100:100 microns.The sintering temperatures of 900℃,950℃ and 1000℃ were applied for each of the mixtures.The results showed that only filters with weight ratio 0.7:0.3 sintered at 900℃,950℃ and 1000℃ had porosity between 35 and 50% with values of 39.41±0.96;40.15±1.59;40.14±1.31 respectively.Mechanical strength,permeability and iron leaching behavior were investigated for these three formulations.The formulation 0.7:0.3 with sintering temperature of 1000℃ had the higher permeability and was the more stable for iron leaching so it is the more adapted for water treatment in terms of flow rate and iron leaching behavior,pore size distribution showed that these filters were macroporous and designed for microfiltration with average pore diameter of 0.46μm.