XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 3087
the flotation of valuable minerals, it is essential to con-
tinue the search for efficient and environmentally friendly
depressants.
Organic reagents or biopolymers, such as dextrin
(starch, dextrin, carboxymethyl cellulose, and chitosan),
polyacrylamides (PAM), and wood extracts (lignosulfo-
nates), have been explored as alternatives in pyrite depres-
sion (Bulut et al., 2011 Mu et al., 2016b). However, they
have not yet completely replaced the cyanide-lime combi-
nation, despite being more environmentally friendly.
This study investigates pyrite depression using sodium
metabisulfite (MBS) and dextrin (DX), both individually
and in combination to enhance the suppression of pyrite
with environmentally sustainable reagents. A fixed pH of
8 was used to reduce lime consumption. The evaluation
was conducted through contact angle measurements and
microflotation tests, to determine the combined effect of
both reagents on pyrite depression.
METHODOLOGY
Materials
In this study, natural pyrite specimens from Guanajuato,
Mexico were used. These specimens were crushed and
manually purified, using an optical microscope to remove
impurities such as calcite, silicate minerals, and other sul-
fide minerals. Two types of samples were employed: 1 cm2
crystals for contact angle measurement and –100+75 µm
particles for microflotation studies. The microflotation
samples were analyzed using X-ray diffraction, polarized
optical microscopy, and atomic absorption chemical anal-
ysis to determine their purity. Figure 1 shows the X-ray
diffractogram of the pyrite sample, highlighting the char-
acteristic peaks of this mineral. Chemical analyses revealed
45.11% iron, estimating a pyrite purity of 97.22%.
Industrial amyl xanthate potassium (PAX) with 94%
purity was used as a pyrite collector without prior purifica-
tion. Tapioca dextrin 12 (from A. E. Stanley Manufacturing
Company) and sodium metabisulfite (from J.T.Baker, ana-
lytical grade) were used as depressants. Fresh solutions of
DX, MBS, and PAX were prepared for all studies. The
experiments were conducted with a constant ionic strength
of 1×10–3 M NaCl. Deionized water was used throughout,
and the pH was adjusted using diluted solutions of NaOH
and HCl, all of which were analytical grade reagents.
Contact Angle Studies
Contact angle studies on pyrite in the presence of dextrin
and sodium metabisulfite were conducted by mounting
mineral crystals in epoxy resin, sanding them with silicon
carbide paper, and polishing to a mirror finish. The crystals
were then sonicated for 5 minutes to remove any residual
reagents or contaminants that might affect the contact angle
measurements. The samples were conditioned in an aque-
ous solution with deionized water under specific chemical
conditions for a predetermined time (3–10 minutes).
Figure 1. X-ray diffraction pattern of the pyrite used for microflotation (PDF:01-071-1680)
the flotation of valuable minerals, it is essential to con-
tinue the search for efficient and environmentally friendly
depressants.
Organic reagents or biopolymers, such as dextrin
(starch, dextrin, carboxymethyl cellulose, and chitosan),
polyacrylamides (PAM), and wood extracts (lignosulfo-
nates), have been explored as alternatives in pyrite depres-
sion (Bulut et al., 2011 Mu et al., 2016b). However, they
have not yet completely replaced the cyanide-lime combi-
nation, despite being more environmentally friendly.
This study investigates pyrite depression using sodium
metabisulfite (MBS) and dextrin (DX), both individually
and in combination to enhance the suppression of pyrite
with environmentally sustainable reagents. A fixed pH of
8 was used to reduce lime consumption. The evaluation
was conducted through contact angle measurements and
microflotation tests, to determine the combined effect of
both reagents on pyrite depression.
METHODOLOGY
Materials
In this study, natural pyrite specimens from Guanajuato,
Mexico were used. These specimens were crushed and
manually purified, using an optical microscope to remove
impurities such as calcite, silicate minerals, and other sul-
fide minerals. Two types of samples were employed: 1 cm2
crystals for contact angle measurement and –100+75 µm
particles for microflotation studies. The microflotation
samples were analyzed using X-ray diffraction, polarized
optical microscopy, and atomic absorption chemical anal-
ysis to determine their purity. Figure 1 shows the X-ray
diffractogram of the pyrite sample, highlighting the char-
acteristic peaks of this mineral. Chemical analyses revealed
45.11% iron, estimating a pyrite purity of 97.22%.
Industrial amyl xanthate potassium (PAX) with 94%
purity was used as a pyrite collector without prior purifica-
tion. Tapioca dextrin 12 (from A. E. Stanley Manufacturing
Company) and sodium metabisulfite (from J.T.Baker, ana-
lytical grade) were used as depressants. Fresh solutions of
DX, MBS, and PAX were prepared for all studies. The
experiments were conducted with a constant ionic strength
of 1×10–3 M NaCl. Deionized water was used throughout,
and the pH was adjusted using diluted solutions of NaOH
and HCl, all of which were analytical grade reagents.
Contact Angle Studies
Contact angle studies on pyrite in the presence of dextrin
and sodium metabisulfite were conducted by mounting
mineral crystals in epoxy resin, sanding them with silicon
carbide paper, and polishing to a mirror finish. The crystals
were then sonicated for 5 minutes to remove any residual
reagents or contaminants that might affect the contact angle
measurements. The samples were conditioned in an aque-
ous solution with deionized water under specific chemical
conditions for a predetermined time (3–10 minutes).
Figure 1. X-ray diffraction pattern of the pyrite used for microflotation (PDF:01-071-1680)