Electrodialytic remediation of fly ash from co-combustion of wood and straw

Abstract

The heavy metal content in fly ash from biomass combustion, such as straw, wood and sludge, often needs reducing before the ash can be used as fertilizer for agricultural land or as a component in the production of construction materials. In this study, fly ash from a boiler fueled with wood chips and straw was treated either by electrodialytic remediation (EDR) directly or by a combination of EDR and pre-wash with distilled water to investigate the possibilities of reducing the heavy metal content and reusing nutrients as fertilizer and bulk material in construction materials. Different experimental set-ups were tested for EDR treatment primarily of Cd and Pb as well as of Cu and Zn.Elemental contents such as K, P and Ni were compared in ash samples before and after treatment.The results showed that pre-washing caused an increase in total concentrations of most heavy metals because the highly soluble fraction, mainly KCl and K 2 SO 4 , was removed. After EDR treatment, the Cd concentration was reduced to below 2 mg kg -1 in all ash samples with high and stable average removal of above 95%, no matter how high the initial concentration was. The amount of Pb removed varied from 12% to 67%. Even though Pb was extracted from the ash samples, its concentrations in the treated ash samples were elevated due to the ash dissolution, except in the case of pre-washed ash treated in a two-compartment EDR cell, where the mass of Pb removed was the highest with a final concentration of about 100 mg kg -1 . The two-compartment EDR cell probably performed better due to a fast acidification process. In addition, this process was less energy-consuming. However, the fast acidification did in turn affect the leaching property of the treated ash, such as As and Ni, exceeding the limiting concentrations. The EDR/pre-wash-EDR treated ash mainly contained quartz, and the X-ray diffraction (XRD) peaks of K salts had disappeared. This shows that the potassium fertilizer potential was lost in the treated ashes, but the quartz mineral is beneficial in construction materials, such as ceramics. The K fertilizer could be recovered from the water after pre-washing and also from the catholyte through chemical operations, including a separation step.

Microbial Stress: From Model Organisms to Applications in Food, Microbiotechnology and Medicine

“…Several techniques have been tested to reduce contamination. The most common are: decomposition treatment with the addition of inorganic acids; phosphoric acid stabilization (Vavva et al, 2017), elution with nitric acid (HNO 3 ) , application with diluted sulfuric acid (H 2 SO 4 ) (Kashiwakura et al, 2010), washing with hydrochloric acid (HCl) (Weibel et al, 2018); using citric acid for stabilization , using chelating agents for electroplating processes (Chen et al, 2015), and using hydrothermal processes (Ullah et al, 2018).…”

Experimental Treatment of Hazardous Ash Waste by Microbial Consortium Aspergillus niger and Chlorella sp.: Decrease of the Ni Content and Identification of Adsorption Sites by Fourier-Transform Infrared Spectroscopy

“…Several techniques have been tested to reduce contamination. The most common are: decomposition treatment with the addition of inorganic acids; phosphoric acid stabilization ( Vavva et al, 2017 ), elution with nitric acid (HNO 3 ) ( Wang Y. et al, 2015 ), application with diluted sulfuric acid (H 2 SO 4 ) ( Kashiwakura et al, 2010 ), washing with hydrochloric acid (HCl) ( Weibel et al, 2018 ); using citric acid for stabilization ( Wang H. et al, 2018 ), using chelating agents for electroplating processes ( Chen et al, 2015 ), and using hydrothermal processes ( Ullah et al, 2018 ).…”

Phytometric characteristics and chlorophyll index of “Paiaguás” grass (Urochloa brizantha) as a function of wood ash doses and soil water stress

“…BRS Paiaguás presents as an alternative for pasture diversification in tropical regions, mainly during the dry season, as it has a high yield of leaves with good nutritive value, resulting in higher weight gains per animal per area (Valle et al, 2013;Euclides et al, 2016). Wood ash has been shown to neutralize soil acidity and provide nutrients such as calcium, magnesium, potassium, phosphorus and micronutrients, which are essential for plant growth and development (Chen et al, 2015;Symanowicz et al, 2018). Most of the bioenergy produced in the world is derived from plant biomass (Souza et al, 2017).…”