Effect Of Natural Organic Matter On The Reduction Of Hexavalent Chromium By Iron-rich Clay Minerals At Different PH

Chromium pollution is a common heavy metal pollutant in the environment.Because the toxicity and carcinogenicity of chromium are closely related to its element valence,the morphological transformation of chromium has received extensive attention in the field of chromium pollution remediation.Previous studies have shown that iron elements such as dissolved ferrous iron,zero-valent iron,iron-bearing minerals such as pyrite,clay minerals,etc.play an important role in the chromium cycle conversion and chromium pollution treatment projects.Clay is generally present in mineral soils and sediments,and its total iron content accounts for about 50% of the total soil / sediment iron content,and the structural iron in the mineral can be reduced,which has a high reactivity and can be used in the environment.The conversion of various heavy metals such as chromium and uranium has an impact.At present,there are many reports on the interaction and reaction mechanism of clay minerals alone with chromium,but there are often many environmental factors such as organic matter and microorganisms in the natural environment.Very few reports have focused on the reduction reaction and mechanism of chromium in the system where multiple environmental factors coexist and they are mostly limited to acidic conditions.In this paper,we studied the effect of chromium-contaminated site in situ organic matter on the reduction of hexavalent chromium by iron-rich clay minerals at four pH values ??from acidic to alkaline,and under neutral conditions,the effect of fulvic acid standard,Humic acid standard and soluble organic matter in black soil of Northeast China on the process of hexavalent chromium reduction by iron-rich clay minerals in different concentration.The research results are as follows:(1)When the pH of the system is between 6 and 8,the reduction rate of hexavalent chromium reduction by iron-rich clay minerals decreases as the pH value increases,but within this pH range,the iron-rich clay minerals have all reduced hexavalent chromium to trivalent chromium at the end of the reaction;(2)When the in-situ organic matter in the chromium-contaminated site is involved in the process of reducing hexavalentchromium by iron-rich clay minerals,the reduction rate is significantly reduced,but the total reduction has no obvious changes,and the reduction rate still decreases with increasing system pH;(3)Under neutral conditions,when the humic acid standard and the soluble organic matter in the black soil of Northeast China intervene to reducing hexavalent chromium by iron-rich clay minerals,the reduction rate decreases with the increase in the concentration of organic matter,and there is no significant change in the total reduction.There is no obvious oxidation and reduction process when the two act on hexavalent chromium and iron-rich clay minerals alone;(4)Fulvic Acid shows a promoting effect on the reduction of hexavalent chromium by iron-rich clay minerals under high concentration conditions,but it has no significant effect on the total reduction.This paper shows that in the organic-rich environment,the use of iron-containing clay minerals as a carrier in the treatment of chromium pollution needs to consider the influence of organic matter on the reduction rate of hexavalent chromium,the total reduction and the reduction products.