In this study, calcium alginate (Ca-Alg) beads, an inexpensive, easily available, biodegradable material, were activated with anionic surfactant and used for the treatment of wastewater contaminated with waste motor oil. First, polyethyleneimine (PEI) was used to bind sodium dodecyl sulfate (SDS) onto the Ca-Alg beads' surface. Three different SDS concentrations (25, 50, & 100 mg/L) were prepared and treated with Ca-Alg beads for 1, 2, 4, 6, and 24 h. SDS binding yield reached equilibrium at the end of the 24 h, and the binding efficiencies of 25, 50, and 100 mg SDS/L were determined 84%, 72%, and 48%, respectively. The effect of pH between 2 and 10 was also investigated on oil adsorption. Maximum adsorption efficiency (77%) was obtained in the range of pH 6-8. After determining the optimum pH value for oil adsorption, the effect of beads amount (2.5-30 g/L) was also investigated on oil removal efficiency. When the amount of beads increased from 2.5 to 30 g/L, the oil adsorption efficiency increased from 77% to 95%. It was also observed that the oil adsorption efficiency increased when the size of the beads decreased from 4 to 1 mm. For the kinetic calculation, three different concentrations (250, 500, &1000 mg/L) of oily solution were prepared, and oil adsorption was investigated versus time. The kinetic studies for the adsorption of the oily solution using SDS functionalized Ca-Alg beads showed the second-order kinetics. When the initial oil concentration increased from 250 to 1000 mg/L, the amount of adsorbed oil molecules increased from 8.34 to 22.12 mg/g. Langmuir and Freundlich isotherm models were used to explain the relationship between adsorbent and adsorbate, and Langmuir isotherm was the most suitable model because of its high regression coefficient (r2 ) value. Column studies were also carried out, and it was concluded that the proposed adsorbent can be used effectively in the treatment of oily wastewater. PRACTITIONER POINTS: Although there are numerous adsorption studies and studies on the use of alginate beads in various fields in the literature, its use in oil treatment has not been found to our knowledge. The study aims to produce a selective adsorbent for the removal of oil from water by functionalizing the surface of the alginate beads with active agents. In conventional adsorption studies, pollutants are transported from liquid phase to solid phase. With the proposed new adsorbent material, oils will be specifically removed from wastewater and used as fuel. Thus, obtaining an organic origin adsorbent with high calorific value constitutes the original value of the study. In addition, no secondary pollutants will emerge after the adsorption process.
Keywords: calcium alginate beads; oily wastewater treatment; surface modification; surfactant; waste motor oil adsorption.
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