Abstract:
Mine tailings (MT) have been a global problem due to the environmental impacts the
waste generates such as air, soil and water pollution. The detrimental impacts include
a global problem such as acid mine drainage (AMD) which has been difficult to cleanup. Several studies have been conducted to find alternative measures in reducing or
mitigating impacts such as AMD and air pollution. Several studies have revealed how
alumino-silicate mineral waste can be used as raw material to produce construction
materials. This study aimed at evaluating the potential of synthesizing a geopolymer
material from Musina copper mine tailings. Tailings were characterized for their
physicochemical and mineralogical compositions using standard laboratory techniques
in order to evaluate suitability in geopolymerization.
First section of the results presented physicochemical and mineralogical
characterization of the Musina copper tailings together with the bioavailability of the
chemical species. It was observed that the tailings are mainly composed of SiO2 and
Al2O3 as the major oxides indicating that they are aluminosilicate material.
Mineralogical analysis revealed dominance of quartz, epidote and chlorite as the major
minerals. The bioavailability assessment showed that largely Cu and Ca are
bioavailable and highly soluble in an aqueous solution while Al, Mg, Ni, Co, Cr and Fe
have a high proportion in non-labile phase.
Second section presented the preliminary results wherein the potential application of
Musina copper tailings in geopolymerization was evaluated. The results showed that
Musina copper tailings can be used to synthesize a geopolymer material. However, it
was recommended that several parameters influencing geopolymerization need to be
evaluated. The third section presented the evaluation of optimum parameters that
influence the geopolymerization process, which include type of alkali activators, alkali
activator concentration, curing temperature, liquid-solid (L/S) ratio and curing regime.
It was observed that a mixture of NaOH:Na2SiO3.5H20 at a ratio of 70:30 yields a better
geopolymer material. The concentration of 10 M NaOH:Na2SiO3.5H20 at a ratio of 70:30
was observed to be the best that yielded the UCS that is acceptable according to SANS1215 standards. When evaluating curing regime, it was found that the material cured
using greenhouse has lower UCS as compared to the material cured using oven. The
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effect of temperature showed that the UCS decreases with increasing curing
temperature. An admixture of river sand and cement was introduced which resulted in
a high UCS of 21.16 MPa when using an admixture of cement. The mineralogical
composition of the geopolymer bricks showed formation of secondary minerals such as
phlogopite, fluorapatite, diopside and actinolite. Batch leaching conducted on the
geopolymer bricks detected high leaching of Na from the bricks.
Based on the findings of the study of the raw MT potential to produce geopolymer
bricks, it was concluded that the material can be used to produce bricks that are within
the SANS 1215 requirements. The study further recommended that the study a focus
on using cylindrical moulds, other alkali activators and a mechanical mixer. It was also
recommended that the greenhouse be restructured to contain heat within the greenhouse
during the evening so as to allow constant temperature within
