Acid mine drainage treatment with novel high-capacity bio-based anion exchanger.

Aminated peat (termed PG-Peat) produced using polyethylenimine and glycidyltrimethylammonium chloride was used for the removal of sulphate from real acid mine drainage (AMD) in batch and column mode sorption studies. In the batch tests, the highest sulphate removal capacity achieved was 125.7 mg/g. PG-Peat was efficient and rapid in sulphate removal from AMD even at low temperatures (2-5 °C), achieving equilibrium within a contact time of 30 min. The PG-Peat column treating real AMD showed even higher sulphate uptake capacity (154.2 mg SO42-/g) than the batch sorption studies. The regenerative and practical applicability of PG-Peat was also tested in column set-ups using synthetic sulphate solutions (at pH 5.8 and pH 2.0). The sulphate uptake capacity obtained was higher in column mode when the solutions were treated at acidic pH (2.0) compared to pH 5.8. This could be attributed to the presence of cationized amine groups on PG-Peat under acidic pH conditions. Almost complete sulphate desorption was achieved with NaCl in the column that treated synthetic sulphate solution at pH 5.8, while the lowest desorption rates were observed in the column that treated acidic synthetic sulphate solution (pH 2).

Development of a process for microbial sulfate reduction in cold mining waters - Cold acclimation of bacterial consortia from an Arctic mining district.

Biological sulfate removal is challenging in cold climates due to the slower metabolism of mesophilic bacteria; however, cold conditions also offer the possibility to isolate bacteria that have adapted to low temperatures. The present research focused on the cold acclimation and characterization of sulfate-reducing bacterial (SRB) consortia enriched from an Arctic sediment sample from northern Finland. Based on 16S rDNA analysis, the most common sulfate-reducing bacterium in all enriched consortia was Desulfobulbus, which belongs to the δ-Proteobacteria. The majority of the cultivated consortia were able to reduce sulfate at temperatures as low as 6 °C with succinic acid as a carbon source. The sulfate reduction rates at 6 °C varied from 13 to 42 mg/L/d. The cultivation medium used in this research was a Postgate medium supplemented with lactate, ethanol or succinic acid. The obtained consortia were able to grow with lactate and succinic acid but surprisingly not with ethanol. Enriched SRB consortia are useful for the biological treatment of sulfate-containing industrial wastewaters in cold conditions.

Synthesis of zerovalent iron from water treatment residue as a conjugate with kaolin and its application for vanadium removal.

This study was aimed at examining the possible utilization of iron-rich groundwater treatment sludge in the synthesis of zerovalent iron (ZVI) as a conjugate with kaolin clay (Slu-KZVI), and its application for vanadium adsorption from aqueous solutions. Iron was extracted from the sludge using 1 M HCl and was used in ZVI synthesis by the sodium borohydride reduction method. The characteristics and performance of Slu-KZVI were compared to a kaolin modified with synthetic iron (FeCl3·6H2O) (Syn-KZVI). Adsorption results showed a competitive performance by both classes of KZVI, with Syn-KZVI slightly outperforming Slu-KZVI. X-ray photoelectron spectroscopy, X-ray diffraction and transmission electron microscopy confirmed the formation of Fe0 on the core-shell structure of both modified adsorbents. In addition, the surface analysis of Slu-KZVI indicated the presence of P and Ca to a small extent, originating from the sludge. Both classes of sorbents performed better in solutions with acidic and neutral pH values (3-7). Surface complexation was thought to be the primary mechanism whereas simultaneous V(V) reduction and Fe oxidation (redox) reactions may also have taken place to some extent. A sorption test with groundwater confirmed that adsorbents were able to reduce vanadium to a very low concentration.

Quaternized pine sawdust in the treatment of mining wastewater.

Mining wastewater was treated using quaternized pine sawdust (QPSD) anion exchanger. The wastewater contained heavy metals (e.g. Sb, As, Co, Cr, Ni, V, U), NO3(-), among others, and a high concentration of SO4(2-). A series of column cycles imitating a real treatment process was conducted (three sorption/desorption cycles, a maintenance cycle with HCl and two sorption/desorption cycles). The effects of contact time and temperature (5°C and 23°C) were studied to assess the applicability of QPSD in the treatment of cold mining effluents. At 5°C, 85% of nickel was removed but the sorption was slower than at 23°C (initial Ni concentration was about 39 µg/l). Nickel was also removed in column efficiently (85-100% reduction). Treatment with HCl during the maintenance cycles did not hinder nickel sorption. Nickel was desorbed with both NaCl and HCl. Contrary to expectations, nitrate was not sorbed. QPSD showed selectivity towards nickel. However, uptake of uranium and cobalt was detected in column. Neutron activation analysis was used to detect metals sorbed onto the QPSD, and uptake of several metals was confirmed.