Pine-derived Biochar as Option for Adsorption of Сu, Zn, Cr, Pb, Ni and Decreasing of BOD5 in Landfill Leachate

Abstract

Landfill leachate is a highly toxic and hazardous form of wastewater due to its complex composition characteristics, e.g. ammonia, metals, organic compounds. Landfill leachate treatment technologies, such as flotation, coagulation/flocculation, precipitation, oxidation, micro-, ultra-, nanofiltration, reverse osmosis, are too expensive, because they require frequent regeneration of the media or generate secondary brine wastes that may pose a disposal problem. In the present study removal of Zn, Ni, Cr, Pb, Cu from Kazokiškės landfill leachate was studied. Kazokiškės landfill is the main site for disposal of Vilnius region municipal wastes. Operator of the landfill is interested in the alternative ways for the primary treatment of the landfill leachate for reducing the load on the expensive reverse osmosis. One of the proposed options for the primary landfill leachate treatment was adsorption by biochar. Due to the high specific surface area, well-developed porous structure and surface functionality biochar has been used as low-cost adsorbent for adsorption of PTEs from aqueous solutions. Biochar was produced from Scots pine (Pinus sylvestris L.) trunk wood (after debarking) by pyrolysis at the highest heating temperature of 700 °C for 45 min in the low-oxygen environment. Laboratory analysis showed that PTEs, such as Zn, Ni, Cr, Pb, Cu, were present in the landfill leachate before water treatment plant. Thus, the aim of the study was to evaluate PTEs (Zn, Ni, Cr, Pb, Cu) removal efficiency by adsorption by pine-derived biochar. Factors, affecting adsorption efficiency, such as biochar particle size (1, 2.5, 4, 5 mm) and dosage of the biochar (1.01, 3.5, 6.05, 9.45, 13.25, 17.82 g/100 ml of leachate) were studied. Effects of the biochar on pH of the landfill leachate, BOD5, PTEs adsorption were analyzed. The findings showed that optimal parameters for decreasing of BOD5 and retention of Cr and Pb were particle size 1 mm and dosage 6.05 g/100 ml of leachate and 1 mm and more than 13.25 g/100 ml of leachate, respectively. No positive effect on Cu and Zn was observed.