A detailed insight into the adsorption efficiency of Cr(VI) by a novel polypyrrole modified kendu (Diospyros melanoxylon Roxb) seed biochar

Abstract

The occurrence of heavy metals in drinking water is a foremost health concern in today’s world. The use of naturally occurring biomass for the removal of toxic pollutants from water is a proficient and inexpensive treatment method. Based on a comprehensive study of the pyrolysis features, pore configuration, chemical functionality, and carbon framework, we report a cost-effective polypyrrole-modified kendu (Diospyros melanoxylon Roxb) seed-derived biochar (PPY-KSC) via oxidative polymerization. The potentiality of hexavalent chromium decontamination from an aqueous solution was assessed by applying PPY-KSC as a bio-adsorbent. Synthetic steps were designed and the reusability of biomass was investigated by taking the minimum toxicity of the environment into account. The 1:1 V/W (volume/weight) ratio of pyrrole and KSC was optimized for the production of PPY-KSC considering the effectiveness of Cr(VI) removal. All the synthesized biochar were characterized following several techniques such as TEM, SEM, FTIR, XRD, Raman, Zeta potential, BET, and TGA analysis. SEM, TEM, and BET analysis proposes that PPY-KSC exhibited a spherical polypyrrole chain with an uneven microporous structure having an elevated surface area (81.55 m2/g) than KSC. PPY-KSC showed efficient Cr(VI) adsorption (98.8%) for 30 mg adsorbent dose in 100 mL of 10 ppm of Cr(VI) solution in 70 min at room temperature. Cr(VI) adsorption was following the pseudo-second-order kinetic model besides obeying the Langmuir isotherm model with R2 = 0.99 and a Langmuir adsorption capacity of 81.96 mg/g. Furthermore, a simultaneous physio-chemical process along with microporous capture governs adsorption. The Intraparticle diffusion model demonstrates the chemical interaction between polypyrrole and chromium through the electrostatic force of attraction. The thermodynamic parameters signify the remediation of Cr(VI) was irreversible, spontaneous, feasible and endothermic. The present approach allows reusability and studies showed that PPY-KSC owes the sorption property being 81.5% efficient up to five consecutive cycles.