Study On Optical Fiber Sensing In Copper Sulfate Acid Solution

The composition of copper electrolyte is one of important parameters in copper electrolysis refining process, which closely affects the quality of cathode copper precipitation. Therefore, it is of significance to realize the on-line measurement of copper electrolyte composition. Optical fiber sensing technology, with many unique advantages, can meet the demand on access and transform of a variety of devices and system. It has been developed rapidly in recent years and applied in more and more fields.In this paper, the relationship between copper ion concentration in the copper sulfate acidic solution and physicochemical indexes, i.e. density, conductivity, p H value, refractive index and kinematic viscosity and the effects of theses physicochemical indexes on the optical fiber sensing has been studied. Using the optical fiber sensing technology, the characteristics of no-stress bending sensor, transmission sensor and lens sensor in copper sulfate acidic solution has been studied and the relationship between the fiber relative transmission coefficient and the copper ion concentration has been obtained. The no-stress bending sensor model has been constructed based on the data. The experimental result has certain positive role for the online test of copper ion concentration in acidic solution and provides the primary exploration for online test of copper electrolytes.The experimental results show that with the increase in concentration of copper ion in the solution, the solution density, conductivity, refractive index and kinematic viscosity increases gradually and presents the linear relationship, and the linear slope gets gradually smaller with the increase in copper ion and sulfate ion ratio. With the increase in concentration of copper ion in the solution, the p H value decreases. With the increase of copper ion and sulfate ion ratio, the p H value of the solution gradually increases near the same copper ion concentration.For no-stress bending sensor, with the increase of concentration of copper ion in the solution, optical fiber transmission coefficient decreases gradually and presents the linear relationship, which shows that the light intensity increases with the increase of solution concentration. For conducting fiber transmission sensor, with the increase in concentration of copper ion in the solution, the optical fiber transmission coefficient decreases gradually and presents index attenuation relationship. For lens sensor, with the increase in concentration of copper ion in the solution, the relative transmission coefficient decreases and presents the linear relationship, which shows the solution transmittance decreases with the increase in solution concentration.The conducting fiber no-stress bending sensor model has been constructed and the relationship between the optical fiber relative transmission coefficient and fiber bending loss coefficient for the relationship is as follows:The optical fiber relative transmission coefficient can be obtained by experimental measurements and the bending loss coefficient can be obtained according to the above model. The refractive index 2nï¿  in the solution and optical fiber interface can be calculated based on the bending loss formula. The copper ion can be calculated based on the refractive index 2nï¿  in the optical fiber interface and the relational expression between copper ion concentration and refractive index. The established model has been successfully applied to predict the copper ion concentration in different copper sulfate acidic solution.