Highly efficient and selective capture of heavy metals by poly(acrylic acid) grafted chitosan and biochar composite for wastewater treatment

By Lixun Zhang, Shengyin Tang, Fangxin He, Yang Liu, W. Mao, Y. Guan. Chemical Engineering Journal, 2019

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Abstract A novel poly(acrylic acid) grafted chitosan and biochar composite (PAA/CTS/BC) for highly efficient and selective capture of heavy metals (HMs) was prepared. PAA/CTS/BC showed efficient and rapid adsorption of Cu2+, Zn2+, Ni2+, Pb2+, Cd2+, Mn2+, Co2+, and Cr3+, well fitted by Langmuir and pseudo-second-order kinetic models, respectively, and it could be applied in a wide pH range (2–7) with high adsorption capacity. Attractively, PAA/CTS/BC showed strongly selective adsorption in the order of Cr3+ > Pb2+ > Cu2+ ≫ Cd2+ > Ni2+ > Zn2+ > Co2+ > Mn2+. The distribution coefficients of Cu2+, Pb2+, and Cr3+ (~104, ~106, and ~107 mL/g, respectively) nearly matched or exceeded that of reported adsorbents in literatures. Surface complexation via inner-sphere complexes with carboxyl, hydroxyl, or amine groups is proposed as the major removal mechanism of HMs by PAA/CTS/BC; however, the covalent bond strength between HMs and oxygen/nitrogen atoms significantly differed among HMs based on the principle of hard and soft acids and bases, essentially determining the adsorption affinity and selectivity of HMs on PAA/CTS/BC. Surface precipitation was also an important mechanism for adsorption of Cr3+ by PAA/CTS/BC. Additionally, Cr3+ adsorbed on PAA/CTS/BC was almost completely resistant to desorption by 0.01 mol/L Na2EDTA solution, while other HMs could be mostly recovered (>80%) by the same method, indicating its promising potential of recycling pure Cr3+ and excellent reusability. Finally, the case study on the treatment of metal finishing wastewater confirmed that PAA/CTS/BC could efficiently achieve both wastewater purification and metal recycling for specific industrial wastewater.

Subfields: Industrial and Manufacturing Engineering, Mechanical Engineering, Water Science and Technology

View Paper: https://www.semanticscholar.org/paper/7fd8578b60e26495e5ea2148bae40f21f0845511