Disposal of Waste CRT Glass Through the Manufacture of Biopolymer-Modified Concrete

Dr. Daeik (Derek) Kim

Project Engineer

LEE & RO, Inc, City of Industry, CA

ABSTRACT

Cathode ray tubes (CRTs) from computer monitors and television sets, which contain a significantly high percentage of lead by weight, represent an enormous hazardous waste problem in the U.S. and worldwide.  As a result, new technologies are needed to cope with CRT wastes and build new markets for their recycled components, by developing commercially viable concrete composites as well as minimizing CRT disposal problems.  In this study, commercially available biopolymers, such as xanthan gum, guar gum, and chitosan, were used to immobilize the lead from CRT glass waste, reducing Pb leachability.  The biopolymers utilized contain a number of useful functional groups such as carboxyl (xanthan), hydroxyl (guar), and amino groups (chitosan), which play an important role in binding and stabilizing lead onto concrete structures.  The use of biopolymers in concrete systems can create a stable interpenetrating cross-linking composite, which will last for many years.  Results from these new composites showed 30% higher compressive strength than standard concrete and a sharp decrease in lead leachability from an amount of several thousand mg/L initially to three-tenths mg/L or lower values (much lower than the EPA standard for hazardous waste of 5 mg/L by the TCLP test), and for some of the composites leachability is below even the standards for drinking water.  This efficient and cost-effective CRT-Biopolymer-Concrete (CBC) composite is a new class of biopolymer-modified material that can potentially perform an important role in confronting the CRT waste stream.