Adsorption Characteristics And Mechanism Of Active Coke In Advanced Treatment Of Dyeing Wastewater

According to the textile dyeing wastewater discharge standards had been further tightened,resulting in the need for upgrading of dyeing wastewater treatment technologies of related companies,and the transformation of treatment projects.However,most advanced treatment technologies for dyeing wastewater are not applicable due to problems such as processing costs and treatment effects.In this paper,dyeing wastewater was treated by adsorption method with activated coke?ACoke?,low-cost and widely used in flue gas purification treatment,which provided a certain basis for the practical application.The ACoke with the best performance was selected statically,and then compared with the special activated carbon?AC?for water treatment.The adsorption mechanism of ACoke and AC was discussed by means of SEM,FT-IR,GC-MS and Boehm titration..The effect of different dosages,adsorption time and pH value on the adsorption performance of ACoke was studied and the best kind of ACoke was found based on the result.The results show that the removal rate of COD for all types of ACoke decreases with increasing pH value;In terms of adsorption rate,bituminous coal has an advantage over anthracite,but in terms of adsorption capacity.The better adsorption performance is reflected on the ACoke with smaller particle size.Under the same conditions,Compound coal ACoke with 4mm particle size removal efficiency of dyeing and finishing wastewater is 4 to 7 times higher than the others.The influent average COD concentration C₀ and chroma were 80 mg/L,80 times,respectively.The adsorption breakthrough point was considered when the effluent COD concentration Ce over 50 mg/L.The results of dynamic adsorption experiments under different values of EBCT show that ACoke and AC have the largest number of empty beds at EBCT is15min,which are 28.5 and 27.9,respectively.Under this condition,the adsorption exhaustion point reaches when the ratio of C_e/C₀?0.85,and ACoke and AC system operating time are 61h and 49h,respectively.In addition,ACoke works better with UV254,and AC works better with color.Using the orthogonal test method with iodine adsorption value as standard,the optimal regeneration conditions for ACoke and AC?heating temperature,time,and loading amount?are determined to be:1000°C,5 min,6 g and 800°C,15 min,6 g.The adsorption kinetics results show that the adsorption behavior of ACoke is more in line with the intraparticle diffusion model,and the pseudo-first order equation can accurately describe the adsorption behavior of AC.Adsorption isotherm experimental results show that the adsorption system of ACoke and AC on wastewater COD is complex,and it has certain degree of agreement with the Langmuir model and Freundlich model.The adsorption pathway has both physical adsorption and chemical adsorption.The SEM images of ACoke and AC before adsorption indicate that the two have different surface morphology.After the adsorption,the accumulation of particulate matter is found on the ACoke surface,but not the AC surface.The BET characterization results show that the total specific surface area of ACoke after regeneration decreases with the regeneration process,while the specific surface area of AC first increases and then decreases.Both the mesopore ratio and pore volume gradually increase.AC surface chemical analysis show basically the same surface functional groups of ACoke and AC,mainly hydroxyl,ester,carbonyl and carboxyl,but AC surface acid functional groups slightly more.From the infrared spectra of AC before and after regeneration,the intensity of the surface functional absorption peak after regeneration significantly reduces,only a little change for ACoke after regeneration.The results of GC-MS show that ACoke is more effective in adsorbing complex organic matter in the dyeing wastewater.The main organic substances in raw water are aromatic hydrocarbons and alkane derivatives and the content exceedes 90%.After ACoke adsorption,the content of these substances reduces by 30%.After AC adsorption,the content is still more than 85%.