Removal Of Petroleum Sulfonate From Aqueous Solution By Coagulation-adsorption Method

In this paper, the water-soluble metal salts were added to alkaline solutions to obtain freshly generated hydroxide precipitates (FGHP). The FGHP particles have a high surface free energy with a small particle size, large adsorptive surface area and a positive surface charge, which can be used to attract negatively charged colloidal particles to remove surfactants in solutions. The surfactant used in this study was the petroleum sulfonate surfactant (PSs). And the active constituent was extracted which is petroleum sulfonate (PS). The constituent of the PS was analyzed by GC-MS. The particle size of the FGMH and the hydroxide precipitates before and after adsorption were characterized by dynamic light scattering (DLS) and Fourier-transform infrared spectroscopy (FTIR). Batch coagulation-adsorption experiments were conducted to determine the effect of contact time, dosage, pH and temperature. Langmuir and Freundlich isotherms were used to analyze the PS adsorption by the FGMH. Moreover, Visual MINTEQ which is an equilibrium speciation model that can be used to calculate the equilibrium composition of dilute aqueous solutions in the laboratory or in natural aqueous systems were used to analyze the disposal mechanism. And the experimental results showed that:(1) According the GC-MS analysis, it can be deduced that there are five kinds of isomerous hendecyl benzene sulfonate, four kinds of isomerous dodecyl benzene sulfonate and four kinds of isomerous tridecyl benzene sulfonate in the PS.(2) Effects of reaction time, dose of the leaching solution and pH were studied in the adding MgCl2to remove surfactants experiments. The results showed that the FGMH was rapid and effective in removing the P S in water solutions. The removal rate reached maximum at60s. The removal rate increased with increasing amount of MgCl2dosage, and the appropriate MgCl2dosage were2.0g/L when the concentration of the PS was200mg/L. And the optimum pH for the FGMH to remove PS was12.3. The removal efficiencies were all over85%for different concentration PS under the condition. (3) The isotherm data was consistent with both the Freundlich and Langmuir models, and the adsorption of PSs and PS by FGHP is a favorable adsorption process. The adsorption reaction was exothermic in nature, and that the solution temperature has a significant effect on PS adsorption. When the temperature was303K, the saturation adsorption capacities of the PSs and PS were all high, which indicated that FGMH displayed superior adsorption capacities to the surfactants.(4) The FT-IR showed that the PS was absorbed by the FGMH.(5) The spectrum of the desorption solution was the same as the original PS solutions, suggesting that the molecular structure of the PS was not changed in the adsorption process. The adsorbed PS can therefore be reused after desorption.(6) According to the analog computation analysis using Visual MINTEQ, the removal mechanism of PS by FGMH is a coagulation-adsorption process involving charge neutralization and surface complexation.(7) According to adding leaching solution of white mud into alkaline solutions, the optimum stir time was60s, the appropriate dosage were1.5g/L. The removal rate of PSs depended significantly on the pH of the solutions. The optimum pH was12.3, and under the optimum conditions the removal efficiency of PSs can be up to90%.