FLOW-INJECTION ANALYSIS OF MWC FLY-ASH LEACHING CHARACTERISTICS

A completely mixed batch reactor leaching method utilizing flow inject ion analysis (the CMBR-FIA method) was developed to study the lead lea ching characteristics of municipal waste combustor fly ash. Flow injec tion analysis (FIA) coupled with atomic absorption spectrophotometry e nabled the determination of lead concentrations at one minute interval s. The pH and oxidation-reduction potential of the solution were conti nuously monitored to characterize the leaching conditions. Automatic t itration was used to alter the solution pH to defined endpoints. The C MBR-FIA method offers the ability to immediately observe alterations t o the leaching solution, and grants the freedom to study a number of p arameters concurrently. The CMBR-FIA method is a rapid and reliable me ans to investigate leaching characteristics. This paper describes the method and demonstrates its use to monitor the leaching of lead from m unicipal solid waste combustor fly ash as a function of pH. Soluble le ad concentrations are shown to increase quickly with decreasing pH. A maximum of 50% of the total lead concentration was available in soluti on at pH 2. This value gradually decreased with time to over 35% of th e total.