دانلود رایگان مقاله انگلیسی حذف فلزات سنگین از فاضلاب اکسیداسیون آندی آلومینیومی توسط فیلتر کردن غشاء - اشپرینگر 2018

Abstract

Aluminum manufacturing has been reported as one of the largest industries and wastewater produced from the aluminum industry may cause significant environmental problems due to variable pH, high heavy metal concentration, conductivity, and organic load. The management of this wastewater with a high pollution load is of great importance for practitioners in the aluminum sector. There are hardly any studies available on membrane treatment of wastewater originated from anodic oxidation. The aim of this study is to evaluate the best treatment and reuse alternative for aluminum industry wastewater using membrane filtration. Additionally, the performance of chemical precipitation, which is the existing treatment used in the aluminum facility, was also compared with membrane filtration. Wastewater originated from anodic oxidation coating process of an aluminum profile manufacturing facility in Kayseri (Turkey) was used in the experiments. The characterization of raw wastewater was in very low pH (e.g., 3) with high aluminum concentration and conductivity values. Membrane experiments were carried out with ultrafiltration (PTUF), nanofiltration (NF270), and reverse osmosis (SW30) membranes with MWCO 5000, 200–400, and 100 Da, respectively. For the chemical precipitation experiments, FeCl3 and FeSO4 chemicals presented lower removal performances for aluminum and chromium, which were below 35% at ambient wastewater pH ~ 3. The membrane filtration experimental results show that, both NF and RO membranes tested could effectively remove aluminum, total chromium and nickel (>90%) from the aluminum production wastewater. The RO (SW30) membrane showed a slightly higher performance at 20 bar operating pressure in terms of conductivity removal values (90%) than the NF 270 membrane (87%). Although similar removal performances were observed for heavy metals and conductivity by NF270 and SW30, significantly higher fluxes were obtained in NF270 membrane filtration at any pressure that there were more than three times the flux values in SW30 membrane filtration. Due to the lower heavy metal (<65%) and conductivity (<30%) removal performances of UF membrane, it could be evaluated as pretreatment followed by NF filtration to protect and extend NF membrane life. The water treated by both NF and RO could be recycled back into the process to be reused with economic and environmental benefits.

Conclusions

In this study, the treatment and reuse approaches of wastewater of the anodic oxidation coating process of the aluminum industry using UF, NF, and RO membranes were investigated. Chemical precipitation was also studied to observe the removal of heavy metals. The summary of findings are stated as follows:

& The wastewater generated by anodic oxidation during aluminum profile manufacturing leads to harsh characteristics regarding pH, heavy metal concentration, and conductivity.

& Low rejection performances were achieved by PTUF membrane with 5000 Da MWCO that the removal efficiencies of aluminum, nickel, and chromium were similar and varied between 54 and 62% at pressure of 7.5 bar. Increase in pressure improved aluminum and nickel rejection but not chromium rejection. Conductivity and TOC removals at 7.5 bar pressure were about 30%.

& The heavy metals of aluminum and nickel were almost completely removed from the raw wastewater with NF270 membrane at pressure of 20 bar. The removal efficiencies of aluminum, nickel, and chromium were 99, 99 and 94%, respectively. Increase in pressure significantly increased the rejection of chromium that the rejection was improved from 66 to 94% at 10 bar and 20 bar pressures, respectively.