Carbamazepine and Diclofenac Removal Double Treatment: Oxidation and Adsorption.

In the present research, the effect of two hybrid treatments, ozone followed by powdered activated carbon (PAC) or PAC followed by ozone (O3), was studied for the removal of two drugs present in water: diclofenac and carbamazepine. In the study, two initial concentrations of each of the contaminants, 0.7 mg L-1 and 1.8 mg L-1, were used. Different doses of PAC between 4-20 mg L-1 were studied as variables, as well as different doses of O3 between 0.056-0.280 mg L-1. The evolution of the concentration of each contaminant over time was evaluated. From the results obtained, it was concluded that the combined treatment with ozone followed by PAC reduces between 50% and 75% the time required to achieve 90% removal of diclofenac when compared with the time required when only activated carbon was used. In the case of carbamazepine, the time required was 97% less. For carbamazepine, to achieve reduction percentages of up to 90%, O3 treatment followed by PAC acted faster than PAC followed by O3. In the case of diclofenac, PAC treatment followed by O3 was faster to reach concentrations of up to 90%. However, to reach yields below 80%, O3 treatment followed by PAC was more efficient.

Efficacy of atrazine pesticide reduction in aqueous solution using activated carbon, ozone and a combination of both.

In this study, the reduction of the emerging organic contaminant atrazine in water, was investigated by adsorption, oxidation and a combination of both technologies. Adsorption tests were performed using method ASTM D3860-98 with two types of activated carbon: powdered activated carbon and granular activated carbon. For the oxidation tests, advanced ozone oxidation technology was used. Finally, in the combined tests, firstly adsorption treatment was applied followed by oxidation and then the order was reversed. We studied the contaminant removal percentage using different treatments at various reaction times. Results for the different treatments under study showed that, for an initial atrazine concentration of 0.7 mg L-1 and a dose of 16 mg L-1 of powdered activated carbon, with contact times of 60 min, 24 h and 48 h, percentage reductions of the contaminant of 81%, 92% and 94% respectively were obtained. For the same concentration of contaminant, but instead using granular activated carbon, the percentage reduction of atrazine at 60 min was 2%, this percentage rising to 34% and 35% after 24 and 48 h of contact time, respectively. For the same initial contaminant concentration, when ozone was applied at a dose of 19.7 mg L-1, and with a reaction time of 18 min, a reduction of atrazine of 93% was obtained, but oxidation by-products were also produced. For the combined treatments, with the same initial concentration of contaminant and the same doses of carbon and ozone as previously indicated, better contaminant reductions were obtained when the treatment started with activated carbon followed by ozone, achieving a 90% reduction of atrazine observing a 17 minute contact time with powdered activated carbon and a 3 day contact time using the granulated carbon. When the order was reversed by starting with ozone, the contact time was 52 min and 4 days, respectively.

The use of combined treatments for reducing parabens in surface waters: Ion-exchange resin and nanofiltration.

In this study, the removal of parabens from waters, using a combined treatment of magnetic ion exchange resins and subsequent filtration through nanofiltration membranes, was investigated. The selected parabens were methylparaben, ethylparaben, propylparaben and butylparaben. Two different magnetic anionic exchanger resins, MIEX® DOC and MIEX® GOLD, and two nanofiltration membranes (NF), NF-90 and DESAL-HL, were tested. The study was carried out using mono and multicomponent systems, using deionized water and natural waters sampled from two different rivers. In this way, competitive and matrix effects could be evaluated. The results showed, that with the combined treatments, higher elimination rates were obtained. The best removal efficiencies were obtained when the DOC resin was combined with both NF-90 and DESAL-HL membranes. Thus, butylparaben and propylparaben reached removal yields around 100% with both membranes, whereas the corresponding values for methylparaben were 91%, when the NF-90 membrane was employed, or 92% when DESAL-HL membrane was utilized. The elimination rates of ethylparaben with the same treatments were 96% with the NF-90 and 97% when the DESAL-HL membrane was combined with the DOC resin. The elimination percentages were higher as the paraben alkyl chain length increased. In addition, no competitiveness or matrix effects were detected. When the MIEX® GOLD resin was used for pre-treatment, membrane fouling worsened which indicated that resin selection needs to be carefully considered to achieve the best results.