Preparation Of Cassava Alcohol Sludge-based Biochar And Its Adsorption Study On Tetracycline In Water

Sludge is the main by-product in the sewage treatment process.Cassava is often used as a raw material for preparing bio-alcohol as an inedible crop in China,and a large amount of organic dehydrated sludge is produced in the production process.In recent years,with the increasing demand for bio-alcohol in China,the annual output of cassava alcohol sludge is rapidly increasing,causing serious pollution to the environment.Since cassava alcohol sludge has a large output and is rich in fat,protein,cellulose and other organic matter,it is a potential matrix material for the preparation of biochar.Based on this,from the perspective of green environmental protection and resource reuse,this article used cassava alcohol sludge as a precursor,strong alkali and weak acid salt sodium bicarbonate as an activating agent to produce cassava alcohol sludge-based biochar.And the study will focus on the material’s adsorption performance and influence mechanism of tetracycline in water.This study is mainly divided into two parts.The first part investigates the influence of different factors during the pyrolysis process of cassava alcohol sludge,and at the same time this section also determines the best pyrolysis conditions,and analyzes its physical and chemical properties through various characterization instruments.In the second part,tetracycline,an emerging antibiotic pollutant,was used as the target to discuss the impact of environmental factors on the removal of tetracycline by the adsorbent,and to analyze the adsorption mechanism and efficiency of cassava alcohol sludge-based biochar for tetracycline adsorption.To investigate the effect of preparation conditions on the performance of cassava alcohol sludge-based biochar,through the preparation of a single factor test,the effects of the three preparation factors on the performance of the adsorbent material were:activation temperature>activation time>addition ratio of raw material to activator.Pyrolysis temperature has a direct effect on the pore development and surface functional groups of sludge-based biochar,and affects the activation effect of different activation methods.A reasonable activation time and the addition ratio of raw materials and activator will increase the stability of the biochar solid phase product.Orthogonal test results show that the best preparation conditions of cassava alcohol sludge-based biochar are:activation temperature is 800℃,mass ratio of sodium bicarbonate activator to sludge raw material is0.5:1,and activation time is 60 min.Characterization analysis showed that,compared with the original sludge,the biochar prepared with sodium bicarbonate as the activator had an increase in BET specific surface area,micropore volume and area,and S_BET was 375.75 m²/g.FTIR analysis showed that cassava alcohol sludge obtianed the functional groups on the surface of the basic biochar are mainly-OH,C=O,C=C,CO and Si-O-Si.Boehm titration shows that the acidic groups on the surface of the adsorbent are 2.07 mmol/g,which is higher than the basic groups of0.93 mmol/g.Heavy metal content analysis（TCLP）showed that the cassava alcohol sludge-based biochar leachate has almost no heavy metal content and will not cause secondary pollution.Zeta potential measurement surface zero point charge p Hpzc is 2.38.EDS analysis showed that the aroma of the adsorbent surface changes large,enhanced hydrophobicity.XRD analysis showed that cassava alcohol sludge-based biochar is amorphous carbon.Environmental factors such as the initial concentration of tetracycline solution,the initial p H of the solution,the biochar addition,and different anions and cations have a certain effect on the adsorption of tetracycline in cassava alcohol sludge-based biochar.The response surface test showed that the significant order of the factors affecting the removal of tetracycline was:tetracycline concentration solution>dosage of biochar>p H>adsorption time.The interaction between the p H of the solution and the amount of biochar added is significant.The optimal process parameters for tetracycline adsorption on biochar are:p H 3.26,tetracycline concentration 53.27 mg/L,biochar consumption 1.39 g/L,and adsorption time 4.05 h.Under the best conditions,the maximum removal rate of tetracycline was 97.87%.After 5 times of adsorption-desorption regeneration,the adsorption capacity of cassava alcohol sludge-based biochar to tetracycline still exceeds 71.4%of the initial adsorption capacity,and it has good regeneration performance.The adsorption process of cassava alcohol sludge-based biochar to tetracycline conformed to the Elovici adsorption kinetic model,its adsorption behavior is heterogeneous adsorption,and there is uneven energy distribution on the surface of the adsorbent.The Langmuir adsorption isotherm model fitted the experimental data more closely good,the maximum equilibrium adsorption capacity is 154.45 mg/g.Intragranular diffusion is the main adsorption rate limiting step in the process of adsorbing tetracycline.Thermodynamic results showed that the higher the temperature,the better the adsorption of tetracycline on biochar,and the adsorption is an endothermic reaction.The adsorption mechanism analysis shows that the adsorption type of cassava alcohol sludge-based biochar to remove tetracycline is mainly physical adsorption,and the adsorption mechanism mainly included hydrogen bonding,electrostatic attraction,π-πaccumulation,pore filling,and van der Waals force.In summary,cassava alcohol sludge-based biochar can effectively adsorb tetracycline in water and can be applied to the treatment of tetracycline antibiotic wastewater.It not only realizes the harmless treatment and reduction treatment of waste cassava alcohol solid sludge,but also realizes the resource reuse of sludge and achieve the purpose of waste control and certain economy.