Study On The Preparation Of Sludge Adsorbent And Its Adsorption Performance For Dyes

Water-based ink printing wastewater dewatered sludge was used as raw material to prepare adsorbents by common carbonization-activation method?C₁?and one-step carbonization-activation method?C₂?.Based on the characterization of adsorbents,the adsorption kinetics and thermodynamic properties of cationic blue X-GRRL dyes were studied by static adsorption experiments.The adsorption effect of adsorbents on mixed dyes and the adsorption effect of adsorbents on cationic blue X-GRRL dyes after thermal regeneration were also investigated.The comparative experiments of C₁ and C₂ show that the adsorption rate and amount of C₂ are better than C₁ under the same conditions.For 300 mg/L cationic blue X-GRRL dye solution,the adsorption amount of C₂ reaches 489.56 mg/g and the adsorption amount of C₁ is 221.85 mg/g.Therefore,C₂ is mainly discussed and studied.Through single factor experiment and response surface experiment,the optimum process conditions for preparing adsorbent C₂ were selected according to the adsorption amount of cationic blue X-GRRL.The dosage of K₂CO₃ was 15 g/L,the dosage ratio of KOH was 1:1(m _{dry sludge}:m_KOH),the carbonization-activation temperature was 700?,and the carbonization-activation time was 120 min.The adsorption capacity of the adsorbent for cationic blue X-GRRL reached 489.56 mg/g,the specific surface area was 258.64 m²/g,the pore volume was 0.362 cm³/g,and the average pore size was 5.594 nm.The pore size of the adsorbent was mainly concentrated in the range of 2-10 nm,with mesoporous structure,which was suitable for adsorbing dye molecules.Energy dispersive spectroscopy?EDS?showed that the adsorbent contained only a small amount of Cu,K,Al and other metal elements.The adsorbent had a certain degree of safety.FT-IR spectra show that the adsorbent has polar groups such as-OH,-NH₂,-C=O.These polar groups can adsorb dyes on the adsorbent by forming hydrogen bonds and ion bonds with dye molecules.The static adsorption experiment of adsorbent C₂ on cationic blue X-GRRL showed that the optimal treatment conditions for cationic blue X-GRRL dye wastewater with concentration of 300 mg/L were adsorption time 420 min,adsorption temperature 25?,pH5.4 and adsorbent dosage 0.6 g/L.At this time,the adsorbent adsorption capacity was489.56 mg/g,and the decolorization rate of the solution reached 97.24%.Kinetic studies show that the quasi-second-order kinetics model can describe the adsorption kinetics of cationic blue X-GRRL by adsorbents.Intra-particle diffusion process is an important factor affecting the adsorption rate,but with the increase of temperature,the effect of intra-particle diffusion of adsorbent decreases,and the adsorption rate constant of intra-particle diffusion increases with the increase of temperature.Thermodynamic studies show that the adsorption of cationic blue X-GRRL by adsorbent is in accordance with Langmuir isothermal equation,mainly monolayer adsorption.Adsorption is an endothermic process??H⁰>0?.Increasing temperature is conducive to the adsorption process,which proceeds spontaneously??G⁰<0?.Adsorption process is accompanied by the increase of adsorption entropy??S⁰>0?.Static adsorption experiments of adsorbents on mixed dyes show that the mixture of cationic blue X-GRRL?CB?and acid orange?AO?is beneficial to the removal rate,and is mixed with CB?200 mg/L?and AO?200 mg/L?.The removal rates of dyes,AO and CB were 99.11%and 99.01%,respectively,while the removal rates of AO and CB in single dye adsorption under the same conditions were 56.89%and 48.59%,respectively;the adsorbents for cationic blue X-GRRL and cationic pink FG The removal rate of the mixed dye is not much different from the single dye removal rate.The optimum regeneration conditions were as follows:temperature 551.7?,time59.35 min,heating rate 10.1?/min,static adsorption capacity before and after multiple regeneration were 475.1 mg/g,345.5 mg/g,256.7 mg/g and 218.5 mg/g,respectively.The results show that the adsorbent prepared from the sludge of water-based ink printing wastewater has good adsorption performance.It can be used as an efficient,safe and economical adsorbent to treat cationic dye wastewater,thus realizing the purpose of sludge recycling and waste treatment..