The Ex-situ Remediation Research Of River Water Polluted By Heavy Metals And PAHs

Humic acid, rectorite and PVA were used to prepare microspheres adsorbent to control combined pollution of heavy metal and PAHs. Effects of microspheres dosage, shaking time, pH value of the solutions, temperature and initial concentration on adsorption of Cu(II), anthracene and phenanthrene were investigated in this paper. The results show that, for the adsorption of Cu(II), anthracene and phenanthrene, the optimum microspheres dosages are 0.005g/mL,0.1g/mL and 0.02g/mL, respectively, the optimum initial concentration of the solutions is 30mg/L, 10 mg/L, 20 mg/L, respectively, Under this condition, adsorption equilibrium was attained within 4h, 14h and 9h, respectively. The pH value and temperature of the solutions need not to be adjusted. The adsorptive capacity of anthracene and phenanthrene increase with Cu(II) concentration, while decrease with o-phthalic acid content.The thermodynamics and kinetics for the adsorption of anthracene, phenanthrene and Cu(II) onto microspheres were discussed. The results shows that the isothermal adsorption law of Cu2+ can well are described by Langmuir and Freundlich models. The adsorption process is spontaneous, exothermic and in-of-order, spontaneous, for Cu2+, exothermic and in-of-order for phenanthrene, unspontaneous,exothermic and in-of-order for anthracene. The kinetics for adsorption of Cu(II), anthracene and phenanthrene onto microspheres conforms to pseudo-first-order, pseudo-second-order, and Elovich and double constants equation. The process of adsorption of Cu(II), anthracene and phenanthrene are all controlled by outer diffusion stage.The adsorptive selectivity sequence of the three heavy metals Cu(II), Cd(II), Pb(II) was inspected. The competitive adsorption among the several substances was discussed. Adsorption mechanism was investigated, too. The results show that the adsorptive selectivity follows the sequence:Cu(II)>Pb(II)>Cd(II).Under the conditions of coexistence of anthracene and phenanthrene, adsorption of phenanthrene on to the microspheres was influenced by anthracene. The adsorptive capacity of Cu(II) was highest under the conditions of coexistence of Cu(II), Cd(II), Pb(II) , anthracene and phenanthrene. The result of infrared spectra analysis shows that the adsorption of heavy metal ions by microspheres caused by chelation of Cu(II), hydroxyl and carboxyl, or chelating of Cu(II) with carboxyl. Adsorption of anthracene and phenanthrene by microspheres caused by hydrogen bond, hydrophobic bond and Van der Wall force.The influence of initial concentration on successive adsorption efficiencies of Cu(II), Cd(II), Pb(II), anthracene and phenanthrene were inspected. The results show that, under the conditions of successive adsorption, the breakthrough volume decrease with the initial concentration of complex pollution solutions, saturated adsorption capacity increased with the initial concentration, the adsorptive capacity becomes greater if the flow velocity of the solutions was slower.The ex-situ remediation efficiencies of river water polluted by Cu(II), Cd(II), Pb(II), anthracene and phenanthrene were investigated. The results show that the breakthrough and saturated volume increase with the height of the column, the breakthrough and saturated adsorptive capacity decrease with the rise of the column height. The microspheres can effectively remove COD, TN and TP from the river water, and the removal rate of TP was highest.