Sven-Uwe Geissen

Selective removal of diclofenac from contaminated water using molecularly imprinted polymer microspheres

A molecularly imprinted polymer (MIP) was synthesized by precipitation polymerization using diclofenac (DFC) as a template. Binding characteristics of the MIP were evaluated using equilibrium binding experiments. Compared to the non-imprinted polymer (NIP), the MIP showed an outstanding affinity towards DFC in an aqueous solution with a binding site capacity (Q(max)) of 324.8 mg/g and a dissociation constant (K(d)) of 3.99 mg/L. The feasibility of removing DFC from natural water by the MIP was demonstrated by using river water spiked with DFC. Effects of pH and humic acid on the selectivity and adsorption capacity of MIP were evaluated in detail. MIP had better selectivity and higher adsorption efficiency for DFC as compared to that of powdered activated carbon (PAC). In addition, MIP reusability was demonstrated for at least 12 repeated cycles without significant loss in performance, which is a definite advantage over single-use activated carbon.

Performance evaluation and application of molecularly imprinted polymer for separation of carbamazepine in aqueous solution

A molecularly imprinted polymer (MIP) for selective adsorption of carbamazepine (CBZ) in aqueous solution was synthesized by precipitation polymerization using CBZ as a template molecule and methacrylic acid (MAA) as a functional monomer. The performance of the CBZ-MIP was evaluated in terms of selectivity, adsorption capacity, binding characteristics, loading volume, and elution volume. The CBZ-MIP exhibited a high affinity for CBZ over the competitive compound (Diclofenac) and was more suitable to remove low concentrations of CBZ in large-volume water samples. A binding performance experiment indicated that the adsorption of CBZ-MIP was characterized by both specific and non-specific binding interactions. Moreover, the regenerability of the MIP was affirmed in ten sequential cycles of adsorption/desorption without a significant loss in recovery. Finally, the CBZ-MIP was applied to enrich CBZ in environmental water samples, and the CBZ concentrations were subsequently determined using HPLC-UV. The results were in good agreement with corresponding LC-MS/MS data.

Catalysed ozonation for removal of an endocrine-disrupting compound using the O3/Fenton reagents system

Aqueous solutions of diethyl phthalate (DEP) were oxidized by using ozone combined with Fenton reagents. The effects of operating parameters such as initial pH; initial concentration of DEP, H2O2 and Fe2+; [H2O2]0/[Fe2+]0 ratio and O3 dosage on the degradation rates of DEP were investigated. The results showed that DEP degradation is strongly dependant on the pH; initial concentrations of the phthalate, H2O2 and Fe2+; [H2O2]0/[Fe2+]0 ratio and O3 dosage. The addition of H2O2 and Fe2+ ions was effective to achieve almost 98% degradation of 200 mg L−1 of DEP in about 40 min using a dose of O3 = 45 g m−3 NTP; [H2O2]0 = 2.5 × 10−2 mol L−1 and [Fe(II)]0 = 5 × 10−3 mol L−1, as compared to over 60 min by using O3 and Fenton processes applied separately. DEP degradation followed apparent pseudo-first-order kinetics under ozonation, Fentons reagents oxidation and the combined ozonation/Fenton reagents oxidation process. The overall reaction rates were significantly enhanced in the O3/Fe2+/H2O2 oxidation system, and allows achieving 100% degradation of DEP (100 mg L−1) in 30 min of reaction time. The notable decrease in DEP removal rate observed in the presence of a radical scavenger indicates that there was an obvious synergetic effect in the combined ozonation/Fenton reagent process most likely because ozonation could accelerate Fenton reagents to generate hydroxyl radical HO•. Thus, the reaction between DEP and HO• proceeds mainly in the bulk of the aqueous phase. Under optimal conditions, the O3/Fe2+/H2O2 system oxidation was the most effective in DEP removal in water.

Model-based performance and energy analyses of reverse osmosis to reuse wastewater in a PVC production site

ABSTRACT A pilot-scale reverse osmosis (RO) followed behind a membrane bioreactor (MBR) was developed for the desalination to reuse wastewater in a PVC production site. The solution–diffusion–film model (SDFM) based on the solution–diffusion model (SDM) and the film theory was proposed to describe rejections of electrolyte mixtures in the MBR effluent which consists of dominant ions (Na+ and Cl−) and several trace ions (Ca2+, Mg2+, K+ and SO42−). The universal global optimisation method was used to estimate the ion permeability coefficients (B) and mass transfer coefficients (K) in SDFM. Then, the membrane performance was evaluated based on the estimated parameters which demonstrated that the theoretical simulations were in line with the experimental results for the dominant ions. Moreover, an energy analysis model with the consideration of limitation imposed by the thermodynamic restriction was proposed to analyse the specific energy consumption of the pilot-scale RO system in various scenarios.

A comparative study on ozone, hydrogen peroxide and UV based advanced oxidation processes for efficient removal of diethyl phthalate in water

Several Advanced Oxidation Processes (AOPs) including O3/H2O2, O3/TiO2, O3/activated carbon (AC), O3/Al2O3, O3/Fe2+/H2O2 and UV/TiO2 have been investigated and compared for the removal of diethyl phthalate (DEP), an endocrine disrupting compound, in aqueous solutions. Hydroxyl radicals were the main species responsible for DEP degradation and this was supported by computational chemistry calculation, scavenger experiments, and LC/MS/MS analysis. The change of the abundance of reaction products over time was determined. Organic acids as well as anhydride and hydroxylated products were found to accumulate in solution even after long reaction time (2 h). Careful choice of the operating parameters (pH, ozone concentration and catalyst dosage) was crucial to achieve enhanced performance of the combined processes above what each oxidant and catalyst can achieve alone. O3/AC process was found to reduce the oxidation efficiency of O3 at high ozone concentrations. Heterogeneous catalytic ozonation with Al2O3 was the most effective process for DEP removal (∼100% removal in about 15 min) and based on pseudo-first-order kinetics at pH7, the studied oxidation processes followed the order: O3/Al2O3(0.093 min-1)>O3/H2O2/Fe2+(0.076 min-1)>O3/AC(0.069 min-1)>O3/H2O2(0.053 min-1)>O3/TiO2(0.050 min-1)> O3 alone (0.039 min-1)>UV/TiO2(0.009 min-1).