Pharmaceutical Residue Hydrochar Prepared By Hydrothermal Carbonization Coupled With Alkali Etching And The Application Of Dyeing Wastewater Purification

Under the background of "dual carbon",the use of fossil resources is gradually decreasing,and organic solid waste becomes an important carbon resources,so the efficient utilization of organic solid waste becomes the important task.The solid waste residue of Chinese pharmaceutical industry has a huge output and a wide range of sources.It contains many organic substances,and has the potential to transform into high-quality carbon materials.Pharmaceutical residue has high water content,high viscosity and complex composition.Therefore,conventional pyrolysis treatment has the problems of high energy consumption and serious waste gas pollution.It is urgent to develop an economical,feasible and environmentally friendly disposal technology.Hydrothermal carbonization(HTC)technology has the advantages of mild reaction conditions,low energy consumption,high carbon yield and stable product performance.It is highly suitable for the treatment of pharmaceutical residue.In this paper,an innovative method of treating pharmaceutical residue using HTC technology coupled with alkali etching is proposed,which can effectively recycle and reduce pharmaceutical residue,and the obtained hydrochar can have magnetic properties without adding additives.The effects of HTC conditions and alkali etching concentration on hydrochar were investigated.Then the hydrochar was applied in the field of printing and dyeing wastewater purification,and the adsorption property and mechanism of hydrochar were investigated.The study takes "Treat waste with waste" as the development concept and explores the industrial application of pharmaceutical residue.The main work carried out in this study is as follows:Firstly,the pharmaceutical residue alkali etching hydrochar was prepared.In view of the characteristics of pharmaceutical residue and the difficulties of disposal and utilization,HTC technology was selected as the basic way of treating pharmaceutical residue.The applicability and feasibility of HTC in the disposal of industrial pharmaceutical residue were verified by using HTC to prepare pharmaceutical residue hydrochar under appropriate solid-liquid ratio.The effect of HTC condition on the physicochemical properties of hydrochar was discussed and the structural properties of the material were characterized.Pharmaceutical residue hydrochar is a magnetic mesoporous material with a maximum specific surface area of 78.7 m2/g.KOH solution etching can effectively increase the surface roughness and regulate the physicochemical properties of hydrochar.In the process of HTC,the rich iron element in pharmaceutical residue is reduced to magnetic Fe3O4 by organic matter,resulting in certain magnetic properties of hydrochar.Secondly,based on the physicochemical properties of pharmaceutical residue alkali etching hydrochar,the hydrochar was used as adsorbent in the dyeing wastewater purification.The adsorption properties of alkaline etching hydrochar on single-component pollutant methylene blue(MB)and multi-component pollutant(MB、Pb2+、Cd2+)were investigated respectively.In the process of alkali etching hydrochar adsorption of single component pollutant MB,the optimal experimental parameters were as follows:HTC temperature was 260℃,HTC time was 2 h,KOH solution etching concentration was 1 mol/L.The maximum surface area of alkali etching hydrochar was 54.64 m2/g,the adsorption capacity of MB was 34.8 mg/g,and the removal rate reached 89.6%.In the multi-component pollutant adsorption,when the KOH solution was 3 mol/L,the comprehensive adsorption performance of hydrochar reached the best level:the highest removal rate of MB was 81.2%,the highest removal rate of Pb2+ was 99%,and the highest removal rate of Cd2+was 84.0%.The kinetic adsorption processes of MB,Pb2+ and Cd2+ can be properly described by the pseudo second-order(PSO)kinetic model,and the isothermal adsorption processes of MB and Pb2+ can be described by Langmuir model.Adsorption experiments show that pharmaceutical residue hydrochar has good compatibility and versatility in removing water pollutants.Finally,the glucose solid waste and pharmaceutical residue were doped by HTC reaction to improve the adsorption performance of co-hydrochar.The glucose waste with high carbon and nitrogen content and pharmaceutical residue in different proportions of co-hydrothermal reaction,which can introduce more carbon and nitrogen elements into the hydrochar products,increasing the heteroatomic functional groups,improving the material surface wettability and optimizeing the adsorption performance of carbon materials.The effects of different glucose waste doping ratio and etching concentration on the physicochemical properties of cohydrochar were investigated.The results showed that the removal rate of Cd2+increased to 93.6%when the proportion of solid waste doping was 50%.Compared with the original pharmaceutical residue hydrochar,the comprehensive adsorption performance of co-hydrochar was significantly improved.Therefore,the utilization of organic solid waste resources can be effectively realized by doping glucose solid waste with pharmaceutical residue to prepare cohydrochar.In this study,the HTC coupled alkali etching technology was used to dispose pharmaceutical residue,which successfully prepared hot carbon and achieved good results in the field of printing and dyeing wastewater purification,which effectively realized the reduction disposal and high value utilization of pharmaceutical residue,and provided a new idea for the resource disposal and sustainable development of industrial organic solid waste.