Research On Adsorption Of Hexavalent Chromium By Iron-loaded Activated Biochar And Its Use As Photocatalytic Carrier

Biochar is an attractive adsorbent due to its wide range of sources,ease of use,reusability and wide range of applications.Therefore,many researchers take biochar as themain body and modify it in different ways to improve its adsorption performance.At the same time,the modified biochar is also an ideal photocatalytic material carrier.Losts of studieshave shown that the biochar based photocatalytic has better removal effect on pollutants in water than the single photocatalytic.Chromium（Cr）is one of typical heavy metals inwastewater.Cr（Ⅵ）has a strong carcinogenicity and mutagenicity,the ecological environment and poses a serious threat to human health,its environmental toxicity is 100 times compared with Cr（Ⅲ）.Therefore,the treatment technology of Cr（Ⅵ）in wastewater is very important.Adsorption is a traditional method of treating heavy metal wastewater with low cost,goodeffect and flexible use conditions,which is suitable for actual wastewater treatment.In this study,biochar with high specific surface area was prepared by a series of pretreatment methods,such as crushing,soaking in alkali solution,cleaning,drying andpyrolysis at high temperature under nitrogen.In addition,acetone was used as the solvent and iron salt was loaded onto it to prepare iron-loaded activated biochar with better adsorptionperformance of Cr（Ⅵ）in aqueous solution.By adjusting the parameters of various conditions in the preparation process,various adsorption materials based on biochar were obtained.Meanwhile,the removal capacity of Cr（Ⅵ）in wastewater was studied and the application effect of the adsorption materials was comprehensively analyzed.The experimental part of this paper is mainly divided into the following three parts:The first part is the preparation and characterization of iron loaded activated biochar.The characterization showed that the surface properties of biochar were greatly improved byactivation treatment.The specific surface area of biochar after alkali activation increased greatly,and the pore structure also increased,which made the subsequent iron salt loading easier.The iron-loaded method is aslo effective,and the reduction of iron exists in theiron-loaded salt process.In the second part,the adsorption experiments of Cr（Ⅵ）in wastewater by differentbiochar were studied.The experimental results showed that the adsorption capacity of Cr（Ⅵ）of these two kinds of materials was higher than that of the original biochar,among which the adsorption capacity of Cr（Ⅵ）in solution by Fe/PBC-ND was 25.68mg/g.The adsorptionbehavior of Cr（Ⅵ）was consistent with Freundlich adsorption thermodynamic model and Elovich adsorption kinetic model,indicating that the adsorption was mainly chemisorption with high chemical reaction energy.At last,by means of several material characterizationmethods,the mechanism of preparing iron-loaded activated biochar and its removal of Cr（Ⅵ）was further speculated.In the third part,the improvement of the photocatalytic degradation of Rhodamine B by iron loaded activated biochar composite with carbon nitride（g-C₃N₄）was studied.Thecomposite was prepared by adding iron loaded activated biochar during the pyrolysis process of g-C₃N₄.The results of photodegradation experiments showed that the addition of biochar kept the high photodegradation efficiency of rhodamine B.Moreover,as a carrier,biochar still plays an important role in the recovery and reuse of photocatalytic materials.