Optimization of reaction conditions for the electroleaching of manganese from low-grade pyrolusite

In the present study, a response surface methodology was used to optimize the electroleaching of Mn from low-grade pyrolusite. Ferrous sulfate heptahydrate was used in this reaction as a reducing agent in sulfuric acid solutions. The effect of six process variables, including the mass ratio of ferrous sulfate heptahydrate to pyrolusite, mass ratio of sulfuric acid to pyrolusite, liquid-to-solid ratio, current density, leaching temperature, and leaching time, as well as their binary interactions, were modeled. The results revealed that the order of these factors with respect to their effects on the leaching efficiency were mass ratio of ferrous sulfate heptahydrate to pyrolusite 〉 leaching time 〉 mass ratio of sulfuric acid to pyrolusite 〉 liquid-to-solid ratio 〉 leaching temperature 〉 current density. The optimum conditions were as follows： 1.10：1 mass ratio of ferrous sulfate heptahydrate to pyrolusite, 0.9：1 mass ratio of sulfuric acid to pyrolusite, liquid-to-solid ratio of 0.7：1, current density of 947 A/m^2, leaching time of 180 min, and leaching temperature of 73°C. Under these conditions, the predicted leaching efficiency for Mn was 94.1%; the obtained experimental result was 95.7%, which confirmed the validity of the model.

Experimental and mechanistic study on chemical looping combustion of caking coal

Under high-temperature batch fluidized bed conditions and by employing juye coal as the raw material,the present study determined the effects of the bed material,temperature,OC/C ratio,steam flow and oxygen carrier cycle on the chemical looping combustion of coal.In addition,the variations taking place in the surface functional groups of coal under different reaction times were investigated,and the variations achieved by the gas released under the pyrolysis and combustion of Juye coal were analyzed.As revealed from the results,the carbon conversion ratio and rate were elevated significantly,and the volume fraction of the outlet CO_(2)remained more than 92%under the oxygen carriers.The optimized reaction conditions to achieve the chemical looping combustion of Juye coal consisted of a temperature of 900℃,an OC/C ratio of 2,as well as a steam flow rate of 0.5 g·min^(-1).When the coal was undergoing the chemical looping combustion,volatiles primarily originated from the pyrolysis of aliphatic-CH_(3)and-CH_(2),and CO and H_(2)were largely generated from the gasification of aromatic carbon.In the CLC process,H_(2)O and CO_(2)began to separate out at 270℃,CH4 and tar began to precipitate at 370℃,and the amount of CO_(2)was continuously elevated with the rise of the temperature.

Controlled Synthesis of Polymers

Controlled synthesis is central to obtaining polymers with accurate structures and excellent performances.Recent research in the controlled synthesis of polymers has focused on optimizing monomers,initiation systems,and reaction conditions.The satisfactory sequence,topological structure,and dispersity have been achieved to satisfy the growing demand for functional polymers.This re-view summarizes the selection of monomers of various types and structures,the innovation of initiation systems,and the optimiza-tion of reaction conditions in the controlled synthesis of polymers and discusses their challenges and opportunities.