One-pot green synthesis of poly(hexamethylenediamine-tannic acid)-bacterial cellulose composite for the reduction, immobilization, and recovery of Cr(VI)

Hexavalent chromium Cr(VI) is one of the most toxic heavy metal pollutants in water due to its high water solubility, high toxicity, strong mutagenicity and carcinogenicity. To enable efficient Cr(VI) removal from wastewater, it remains difficult to fabricate advanced adsorbents with good selectivity and high adsorption capacity in large scale. Herein, a poly(hexamethylenediamine-tannic acid)-bacterial cellulose (denoted as HTA-BC) composite was prepared by using natural raw materials with abundance, low cost and nontoxicity in a facile one-step method and applied for the decontamination of highly toxic Cr(VI). The as-synthesized HTA-BC functionalized with abundant amino and phenolic hydroxyl groups had demonstrated high capacity (534.8 mg g(-1)) and good selectivity for Cr(VI) scavenging. Notably, the treatment of real water samples with the HTA-BC composite could efficiently reduce the concentration of the spiked Cr(VI) below the acceptable levels for drinking water. Moreover, high-purity Cr2O3 was obtained by calcination of the Cr species-laden HTA-BC to ensure that the toxic Cr(VI) residing in the spent adsorbents can't leak out into the surroundings, thus avoiding the secondary pollution. The natural abundance, low cost, easy availability, and sustainability of the raw materials, combined with the facile and green synthesis endowed the HTA-BC composite with great potential for not only decontaminating Cr(VI) wastewater, but also recycling Cr by calcination of the Cr-laden HTA-BC. Moreover, no secondary pollution would be brought during the synthesis and the post-treatment after the Cr(VI) removal, thus it is expected to be a green and sustainable approach for the purification of Cr(VI) containing wastewater.

Automated summary

The HTA-BC composite, synthesized from natural raw materials, exhibited high capacity and selectivity for removing toxic Cr(VI) from wastewater. Furthermore, the calcination of the Cr-laden HTA-BC produced high-purity Cr2O3, preventing secondary pollution and showing potential for recycling Cr. This green and sustainable approach avoids secondary pollution and has great potential for purifying Cr(VI) containing wastewater.