Application of natural and tailored minerals to the treatment of thermomechanical paper mill white water
Buildup of dissolved and colloidal substances in closed white water systems is detrimental to machine runnability and product quality. This research investigated the technical feasibility of using natural and tailored minerals for treatment of synthetic process water (approximately 40 mg/L of dehydroabietic acid (DHA)) and three simulated thermomechanical paper mill white waters. Treatment of synthetic process water with 20 g/L of natural minerals, ground to less than 0.180 mm aggregate size,
... sulted in maximum DHA removal of 55%. Tailored minerals were prepared by mixing zeolites with short-chain and long-chain organic cations. When applied in doses less than the external cation exchange capacity (CEC) of zeolites, cations were firmly bound through coulombic interactions on the external surfaces only. Only long-chain hexadecyltrimethylammonium (HDTMA) cations improved the uptake capacity of zeolites for DHA. Partitioning of DHA into the HDTMA layer was strongly dependent on the mineral concentration and CEC value. HDTMA-tailored minerals with CEC values above 90 meq/100 g ensured complete removal of DHA from synthetic process water. Application of 75 g/L of HDTMA-tailored heulandite to the treatment of white water (pH 7) containing 2270 mg/L of suspended solids, 25 mg/L fatty acids (FA) and 84 mg/L resin acids (RA), resulted in 35% reduction of FA, 28% RA, 24% soluble chemical oxygen demand, 18% total organic carbon and 10% dissolved organic carbon. Constituents, measured as chemical oxygen demand, total dissolved solids and total dissolved volatile solids, were not removed because of the low surface area of heulandite covered with HDTMA cations. The HDTMA layer most likely selectively rejected high molecular weight substances.