One-step synthesis of amino-functionalized attapulgite clay nanoparticles adsorbent by hydrothermal carbonization of chitosan for removal of methylene blue from wastewater

• A green synthesis strategy of one-step HTC process was developed for the preparation of ATP@CCS adsorbent.
• Two low-cost, ecofriendly materials (i.e., ATP, rich in nature and chitosan, a cheap, green chemical) were used as raw material.
• The maximum adsorption capacity could be up to 226.24 mg g−1 at 318.15 K.
• The presence of ionic strength had no significant effect on the MB adsorption.
• The ATP@CCS could be regenerated easily and reused for five times without visible loss of its original capacity.

A new kind of amino-functionalized attapulgite clay nanoparticle adsorbent (ATP@CCS) was fabricated by hydrothermal carbonization of chitosan at a mild temperature and their application for the Methylene Blue (MB) removal from wastewater was studied in this work. Characterization of material was examined by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscope (SEM) and zeta potential analysis. The adsorption properties of the ATP@CCS was investigated as a function of pH of solution, ionic strength, contact time, initial concentration of MB and temperature. It is revealed that the composites pretreated in the solution with higher pH value exhibited larger adsorption capacities. The ionic concentration in MB solution slightly impacted the removal of MB by the ATP@CCS composite. Kinetic studies showed that the composites could adsorb MB rapidly and reached the equilibrium in 120 min, the adsorption process followed pseudo second order kinetics and involvement of particle diffusion mechanism. Adsorption isotherms indicated that Langmuir model was more suitable than the Freundlich model for well elucidation of the experimental data, the calculated maximum adsorption capacity could be up to 215.73 mg g−1 at 318.15 K. Moreover, thermodynamic analysis indicated an exothermic nature of adsorption and a spontaneous and favorable process. Regeneration experiments revealed that the ATP@CCS could be regenerated easily and reused for five times without visible loss of its original capacity. The study suggests that the ATP@CCS is a promising adsorbent for removal of cationic dyes from aqueous solution.

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