Abstract:
Drinking water treatment sludge, a byproduct of the coagulation process in water
purification plants, offers potential for sustainable reuse in environmental
remediation. This study investigates alum sludge as a cost-effective adsorbent for
removing Linear Alkylbenzene Sulfonate (LAS), a common anionic surfactant in
laundry wastewater. Due to its persistence and toxicity, improper discharge of LAS
poses serious ecological risks. This study proposes an eco-friendly approach by
repurposing waste sludge to eliminate such pollutants. Characterization studies of
sludge showed a loamy sand texture with a pH of 7.42 ± 0.06, bulk density of
0.64 ± 0.1 g/cm³, particle density of 2.00 ± 0.4 g/cm³, porosity of
0.68 ± 0.1, and point of zero charge (PZC) of 6.60 ± 0.04. Batch adsorption
studies were conducted using the Methylene Blue Active Substances (MBAS)
method to evaluate LAS removal under varying particle sizes, sludge dosages,
contact times, and pH levels. Fine particles (<0.5 mm) achieved the highest
removal efficiency (47.04 ± 1.32%), while coarser particles (>3.2 mm) were
less effective. Adsorption efficiency increased with higher sludge-to-solution
ratios, peaking at 99.52% at a 1:2 ratio; beyond this, no significant improvement
occurred. Contact time studies found optimal removal (99.49 ± 0.20%) at 60
minutes, after which equilibrium was reached. Lower pH (acidic pH) favored the
adsorption process, and adsorption data fit the Langmuir isotherm model,
suggesting monolayer surface coverage. These results highlight the potential of
alum sludge in removing LAS from contaminated water, providing a low-cost,
sustainable alternative to traditional adsorbents. The study supports waste
valorization and lays the groundwork for eco-friendly surfactant removal methods
using readily available industrial byproducts.
