Phosphogypsum (PG)
constitutes a form of solid byproduct emanating
from the manufacturing process of wet-process phosphoric acid. The
fabrication of one metric ton of wet-process phosphoric acid entails
the generation of approximately five tons of phosphogypsum, a highly
prolific and economically viable waste stream. If we can effectively
solve the problem of poor hydrophobicity of phosphogypsum, it is possible
to replace cement and other traditional cementitious materials. In
this way, we can not only improve the utilization rate of phosphogypsum
but also obtain significant economic and environmental benefits. In
the present investigation, hydrophobic surface coatings were synthesized
and applied onto the surface of α-hemihydrate phosphogypsum
(α-HPG) utilizing sol–gel processing and impregnation
techniques. After hydroxylating α-HPG with alkaline solution
(OH-α-HPG), titanium dioxide nanoparticles (TiO
2
)
hybridized with perfluorodecyltriethoxysilane (PFDTS) were grafted
on its surface. The assessment of the hydrophobic properties of the
coatings was conducted through water contact angle measurements, Fourier
transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy
(XPS), and scanning electron microscopy (SEM) analyses. The contact
angle remained above 124.2° after strong acidic and alkaline
immersion and 50 tape adhesion experiments with good chemical stability
and durability, and the mechanism of surface hydrophobicity modification
was discussed. The experimental outcomes demonstrated a notable increase
in the hydroxyl group concentration on the α-HPG surface following
hydroxylation, significantly enhancing the attachment rate of PFDTS
and TiO
2
onto the HPG surface. PFDTS and TiO
2
can undergo chemical interaction with hydroxyl groups, facilitating
their robust adsorption onto the surface of OH-α-HPG through
chemisorption mechanisms. After bonding the OH-α-HPG surface
with PFDTS and TiO
2
via hydrogen bonding, the otherwise
hydrophilic α-HPG surface acquired excellent hydrophobicity
(OH-α-HPG-PT, contact angle (CA) = 146.7°). The surface
modification of α-HPG through hydroxylation and hydrophobicity
enhancement significantly augmented the compatibility and interfacial
interplay between α-HPG and PT. This research successfully enhanced
the hydrophobic properties of α-HPG, profoundly showcasing its
immense potential within the construction industry and the realm of
comprehensive solid waste utilization.