Abstract: This invention provides for the recovery of lignin and other by-products from the pulping of fibrous plant material. In accordance with this invention, solvents and filtrates are recovered and recycled for reuse. This results in significant solvent and energy savings. Filtrates from the bleaching and delignification of the pulp are recycled for reuse in pulping, separation, and recovery of lignin and other by-products which results in significant energy savings and mitigation if not the elimination of pollution typically associated with bleaching. This invention also relates to products derived from the process and apparatus for carrying out the process. Lignins of various molecular weights and by-products of the pulping process are also recovered. The lignins are precipitated in high yields and at a high rate from a black liquor produced by pulping wood at high temperature and pressures. As a by-product of this process a purified furfural product is recovered.

Abstract: A process for cleaning fouled separation membranes such as ultrafiltration, reverse osmosis, and microfiltration membranes is provided comprising: removing a separation membrane having a fouled surface from operation; effecting reaction on the fouled surface of said membrane of an inorganic peroxide and an alkali metal or alkaline earth metal hypohalite; and thereafter, substantially removing the foulant and the reaction products thereof from the membrane surface.