Synthesis and Performance of Granulated Blast Furnace Slag (GBFS) Based Geopolymers on Copper Removal from Aqueous Solution

The presence of large quantities of heavy metals such as copper in the industrial
waste water poses harms to the human health and environment. This has become a
concern and industry are searching for low cost adsorbents to treat and remove heavy
metals from waste water. Past studies have shown the potential of geopolymers as
potential adsorbent due to its amorphous and porous structure. In this study,
geopolymers from granulated blast furnace slag (GBFS) were synthesized. The
geopolymers were synthesized with a mixed designs of different silica ratio of alkaline
activator. It was found that different silica ratio of alkaline activator created a different
form of geopolymer. The optimum ratio is chose based on the porosity volume.
Another study is done by modifying the GBFS based geopolymer with pore forming
agent; poly ethylene glycol (PEG) and hydrogen peroxide (H2O2) which improved the
copper removal. GBFS based geopolymers, PEG incorporated geopolymer and H2O2
incorporated geopolymer synthesized were characterized for porosity and surface area,
surface images, particle size and thermal stability before being utilized for batch
adsorption test of copper. Batch adsorption tests were conducted on copper sulphate
solution and the adsorbent dosage, contact time and pH were varied. The optimum
silica ratio of the GBFS based geopolymer was the GP-0.75. Meanwhile, the amount
of PEG and H2O2 added were based on previous researches; 3% of PEG to PEG
incorporated geopolymer and 8% of H2O2 to H2O2 incorporated geopolymer. The
percent removal of copper for GBFS based geopolymer was only up to 70% while
geopolymers with pore forming agent could achieve up to 80%. The adsorption
activities for GP-0.75 fitted pseudo second order kinetic models while for GP-0.75
PEG and GP-0.75 H2O2 fitted the pseudo first order kinetic model. So forth, GP-0.75
fitted well in Freundlich isotherm while GP-0.75 PEG and GP-0.75 H2O2 fitted well
in Langmuir isotherm for the isotherm equilibrium study.