Biochar Promotes Arsenopyrite Weathering in Simulated Alkaline Soils: Electrochemical Mechanism and Environmental Implications.
Shuai WangPeng LiaoLing CenHongguang ChengQingyou LiuPublished in: Environmental science & technology (2023)
Oxidation dissolution of arsenopyrite (FeAsS) is one of the important sources of arsenic contamination in soil and groundwater. Biochar, a commonly used soil amendment and environmental remediation agent, is widespread in ecosystems, where it participates in and influences the redox-active geochemical processes of sulfide minerals associated with arsenic and iron. This study investigated the critical role of biochar on the oxidation process of arsenopyrite in simulated alkaline soil solutions by a combination of electrochemical techniques, immersion tests, and solid characterizations. Polarization curves indicated that the elevated temperature (5-45 °C) and biochar concentration (0-1.2 g·L -1 ) accelerated arsenopyrite oxidation. This is further confirmed by electrochemical impedance spectroscopy, which showed that biochar substantially reduced the charge transfer resistance in the double layer, resulting in smaller activation energy ( E a = 37.38-29.56 kJ·mol -1 ) and activation enthalpy (Δ H * = 34.91-27.09 kJ·mol -1 ). These observations are likely attributed to the abundance of aromatic and quinoid groups in biochar, which could reduce Fe(III) and As(V) as well as adsorb or complex with Fe(III). This hinders the formation of passivation films consisting of iron arsenate and iron (oxyhydr)oxide. Further observation found that the presence of biochar exacerbates acidic drainage and arsenic contamination in areas containing arsenopyrite. This study highlighted the possible negative impact of biochar on soil and water, suggesting that the different physicochemical properties of biochar produced from different feedstock and under different pyrolysis conditions should be taken into account before large-scale applications to prevent potential risks to ecology and agriculture.
Keyphrases
- heavy metals
- sewage sludge
- risk assessment
- health risk
- anaerobic digestion
- human health
- health risk assessment
- plant growth
- drinking water
- organic matter
- gold nanoparticles
- climate change
- municipal solid waste
- mass spectrometry
- antibiotic resistance genes
- electron transfer
- ionic liquid
- ultrasound guided
- magnetic resonance
- simultaneous determination
- liquid chromatography