Process for the recovery of tannin from a spent solution from vegetable tanning baths for leather, and plant for implementing the said process

摘要

Process and corresponding plant for the recovery of tannin from a spent solution from vegetable tanning baths for leather. The process comprises the stages of prefiltering the spent solution A from the baths to retain tannin-free wastes B and releasing a prefiltered solution containing tannin C; thorough filtration of the prefiltered solution C with discharge of the tannin-free permeate liquid D and retention of a concentrated solution E which is recycled to further increase the concentration. The recycled liquid E is thermostatted and once the predetermined concentration has been achieved it is returned G to the tanning baths. The membranes present in the ultrafiltration unit 11 are washed with water H to prepare them for subsequent filtration. IMAGE