Leaching Behaviour Of Impurities In
Waste Gypsum Board
Author(s)
M. Tafu & T. Chohji
Abstract
Gypsum board is widely used as a building material in many countries. In Japan,
three million tons of gypsum board is manufactured for building construction,
and about one million tons of waste gypsum board is generated from demolition
work. Most waste gypsum board has been placed in landfill sites. Recycle
processes of waste gypsum boards are needed because of a lack of landfill
capacity. To improve the recycle ratio, waste gypsum board is recycled not only
into gypsum board but also into other products, such as roadbed materials. Waste
gypsum board must be clean from contaminants for recycling. Contaminants
such as wood, plastic, metal and asphalt in waste gypsum board are separated
from it. However, waste gypsum board contains some chemical impurities in it.
When the waste gypsum board is applied to roadbed materials, the impurities can
leach from gypsum into ground water; therefore, leaching behaviour of
impurities in gypsum is important. Chemical equilibrium tells us important
useful information about how to dissolve gypsum. In this study, we developed a
novel method for estimating leaching behaviour of waste gypsum based on the
chemical equilibrium and experimental studies. From results of chemical
equilibrium assessments, it is apparent that gypsum turns to calcium carbonate in
a solution containing carbonate ion at alkaline pH, and releases sulfuric ion and
various impurities. Experiment results showed that waste gypsum board easily
dissolved and leached various impurities in the alkaline solution by the addition
of carbon dioxide gas.
Keywords: gypsum board, impurities, chemical equilibrium, recycle.
Keywords
gypsum board, impurities, chemical equilibrium, recycle.
Related Book
Other papers in this volume
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