Fibrous catalysts and sorbents for destruction of toxic organic pollutants in wastwaters

Abstract

Methods of production of a fibrous catalyst and ion-exchange sorbent were developed and patented at St.Petersburg State University of Technology and Design (SUTD). A knitted fabric (mesh) was used as catalyst as well as sorbent support. The knitted structure of the support provides an extensive mass- and heat- transfer area for the catalyst. The mesh consisted of polypropylene monothread (58-60%) and polyacrylonitrile complex thread (40-42%) with linear densities of 64.3 and 27.2 tex respectively. PAN thread is synthesized from: acrylonitrile (92.3 %), methylmetacrylate (6.2 %) and itaconic acid (1.5 %). Polypropylene monothread gives incompressibility and flexibility to the mesh, so that the catalyst/fibrous sorbent could be folded in a variety of shapes to fit the reactor. The production of PAN fibrous catalyst was performed using hot aqueous solution of hydrazine and hydroxylamine in three steps. The modification results in formation of functional groups that can strongly ligate a multivalent metal (such as iron) to the fibre. The activity of the developed catalyst was investigated towards degradation of an anionic detergent (Sulfonol-NP). The experiments were performed at a room temperature and pH=3 using oxygen of air and hydrogen peroxide as oxidants. The greatest destruction degree of Sulfonol was 87-90%. Activation energy of Sulfonol catalytic oxidation calculated using the experimental data is 32 kJ/mol. The other modification of PAN includes treatment of PAN/PP mesh with aqueous mixtures of hydroxylamine and ethylenediamine and produces a ion-exchange sorbent. Identification of functional groups of the modified PAN was performed by means of FTIR spectroscopy. Formation of amino-, amido- carboxilate groups was detected. The modified PAN fibre is an ampholyte. Depending on the modification parameters (pH of modification solution and duration of the process) cation and anion exchange capacities of the sorbent are 2.7 - 3.4 and 0.7 - 1.2 mmol/g respectively.