Poorly humified peat as an adsorbent for metals in wastewater

Abstract

Metal adsorption and surface charge determinations were performed previously on well-characterised Sphagnum and Carex peat samples. The aim of this investigation was to determine metal adsorption from complex wastewaters onto these peat samples and compare it to the adsorption onto peat granules, clinoptilolite, glauconite and a flue dust from steel production. A sulphide mine leachate, a landfill leachate and a laundry wastewater were chosen, giving a variation in pH, ionic strength, total organic carbon and concentrations of metals. Metal adsorption was determined in batch and column experiments. The wastewater composition was of great importance for metal removal efficiency, mainly due to the difference in dominating metal species. In the sulphide mine leachate, containing free metal ions, a high metal adsorption was observed onto both peat and inorganic adsorbents. In the landfill leachate the metals formed carbonate and organic complexes and a low metal removal was achieved. Contrary to the leachates, the laundry wastewater contained suspended particles. The high amount of metals removed, 80% of the Cu and 30-60% of the Zn concentration, was probably withdrawn bound to the particle fraction. The highest removal of metal ions was obtained in the sulphide mine leachate with Carex peat, removing 97-99% of the Zn and 85-100% of the Cu content. The Sphagnum peat sample removed 37-77% of the Zn and 80-100% of the Cu content. The differences found between Sphagnum and Carex peat were attributed to the original chemistry of the plant material and the habitat conditions at the time of peat formation. Generally, the combination of glauconite or clinoptilolite with the peat samples in column experiments gave a minor improvement in metal removal. r

Mechanisms of competitive adsorption of Pb, Cu, and Cd on peat

“…The results suggest that the affinity of Pb for peat were higher than that of Cu and Cd. The respective optimum pH for adsorption of Pb, Cu, and Cd on peat was graphically determined as 4, 4, and 6, which correlated with the results of Brown et al (2000) and Ringqvist et al (2002). The different maximum adsorption pH of Pb, Cu, and Cd highlights the importance of pH in the treatment of wastewaters containing different metals.…”

Municipal Wastewater Treatment With Bentonite From Milos Island, Greece

“…Recently, low cost materials, including rice-husk, maple sawdust, soya cake, coal ash, peat and bone char, have been investigated as adsorbents for wastewater treatment (Ahsan et al, 2001;Daneshvar et al, 2002;Ringqvist et al, 2002;Daifullah et al, 2003;Yu et al, 2003;Kirk et al, 2003). Additionally, the purification of industrial and urban wastewaters using a HEU-type zeolite (clinoptilolite) has been successfully applied (Filippidis et al, 2008a, Filippidis et al,2008b.…”

Characterization and Comparison of Saprist and Fibrist Newfoundland Sphagnum Peat Soils

“…Poorly humified or fibrist peat (horticultural peat) has been well studied as an adsorbent for heavy metals [27][28][29] although the highly humified or saprist peat has not been studied to the same extent and the peat-metal bonding mechanisms have not been fully understood or Activated Carbon ~2.54 (production, quality and source dependent) [11] Zeolites 0.03 -0.14 (quality and end-use dependent) [12] Clay 0.03 -0.375 (quality and type dependent) [13] Peat 0.024 -0.052 (peat type and processing level dependent) [14] established [30], possibly due in part to the destructive characterization procedures employed. Saprist peat can be used as an agricultural enhancement for improving the water holding capacity of sandy soils [23] and possess a higher metal adsorptive capacity than the widely studied fibrist peat [31].…”