Study On Formation And Stability Of Natural Organic Matter-Antimony-Iron Colloid In Acid Mine Drainage

Due to the migration and cumulative variability of antimony（Sb）in acid mine drainage（AMD）,Sb pollution caused by the change of environmental medium has been widely concerned.As an important pollutant adsorption and transport carrier in the environment,Colloid plays a key role in the migration and transformation of Sb in natural water.Studies on the interaction between natural organic matter（NOM）and Sb are mainly focused on the oxidation of organic matter and Sb as well as the formation and influence of NOM-Sb（III）complex,and most of the studies are focused on neutral conditions.The mechanism of NOM-Sb（III）colloid formation and aggregation stabilization in acid mine wastewater containing NOM has not been studied.And in the process of AMD repair,p H gradually from acidic to neutral,environmental changes,and how the formation and migration of colloid,is not clear.Based on this,this study explored the formation and stability mechanism of NOM-Sb（III）colloid in AMD from the perspective of colloid science,revealed the environmental geochemical behavior of NOM-Sb（III）colloid in acidic mine wastewater,and explained the formation and migration of NOM-Fe-Sb colloid under different C/Fe molar ratios and different p H conditions.This study will help deepen the understanding and understanding of Sb in acid mine wastewater rich in organic matter,provide new insights for Sb migration and transformation in AMD,and provide theoretical guidance for Sb pollution prediction and prevention.Therefore,this paper mainly carries out the following work through batch experiment combined with actual AMD and column experiment method,and mainly obtains the following aspects of understanding:（1）In the NOM-Sb（III）colloid formation experiment,different sources of NOM formed different NOM-Sb（III）colloid under the condition of p H3±0.2,humic acid（AHA）formed more colloid with Sb than fulic acid（FA）,and Sb mainly existed in the dissolved form under this condition.（2）In the effect of NOM-Sb（III）colloidal aggregation,due to different sources of NOM,NOM-Sb（III）colloidal suspension in different electrolyte solutions will have different degrees of aggregation and complexation.FA is more sensitive to Fe（III）and Fe（II）,while AHA is more sensitive to Ca²⁺and Mg²⁺.When NOM-Sb（III）was introduced into actual AMD for aggregation kinetics,aggregation complexation was observed,and its stability was strongly dependent on electrolyte concentration.AHA-Sb（III）colloid had a more dominant effect on aggregation in actual AMD than FA-Sb（III）colloid.This advantage may also be influenced by other ions besides the study.（3）NOM-Fe-Sb colloid formation is mainly dependent on AHA and Fe（III）concentration.Colloid can be formed under different C/Fe molar ratios.It was found that the change trend of colloid decreased with the increase of C/Fe mole ratio,and the decrease of gel size was the increase of granular state.The presence of Fe（III）would produce some free radicals with oxidation activity,which would transform the Sb（III）in the colloid into Sb（V）with higher order stability.The formation of nom-Fe-Sb colloid is also affected by different p H.When p H>4,Fe（III）and Sb（OH）3 particles mainly form Fe（OH）₃（S）and Sb（OH）₃ particles,and adsorptive co-precipitation occurs,but colloid cannot be formed.When p H≤4,Sb and Fe（III）mainly exist in colloidal form.（4）In the migration of NOM-Fe-Sb colloid under different p H conditions,the ionic strength will affect the aggregation stability of the colloid.When p H>4,antimony and iron are deposited as particles at the bottom of the column and cannot migrate upward in the quartz sand column.No Sb and Fe（III）contents are detected in the suspension at the exit of the column.When p H≤4,the Zeta potential of NOM-Fe-Sb colloid becomes larger gradually,which makes the colloid have stronger electrostatic repulsive force,which is conducive to the migration of AHA-Fe-Sb colloid in the medium,and leads to the increase of the outflow ratio of Sb and Fe（III）.The results of this study will help deepen the knowledge and understanding of Sb in acid mine wastewater rich in organic matter,provide new insights for Sb migration and transformation in AMD,and provide theoretical guidance for Sb pollution prediction and prevention.