**1. Introduction**

Hexavalent chromium (Cr(VI)), a typical toxic contaminant, is normally discharged by industrial plants, which has strong teratogenicity and carcinogenicity [1–3]. Various technologies have been developed and, among them, adsorption is a popular choice for Cr(VI) owing to its feasibility of operation and cost effectiveness [4–11]. The adsorbent is very important in the adsorption technique, but the current adsorbent mainly suffers from the trade-off between mass transfer and recoverability [12–15]. Typically, high mass transfer requires a good dispersion of adsorbent, but this would decline the recovery efficiency. While high recoverability needs relatively strong noncovalent interaction between adsorbent building blocks, which in turn brings down mass transfer.

Bacteria cellulose (BC), a naturally nanofiber-arranged hydrogel, is a promising candidate adsorbent, exhibiting high mechanical strength and chemical stability [16–23]. Moreover, the highly porous network is of high advantage in boosting the mass transfer within bacteria cellulose. Most recently, a polymer with rich functional groups was adopted to modify the bacteria cellulose to improve the adsorption performance. For example, Jin, X et al. and Wang, J et al. used polyethyleneimine to graft on the bacteria cellulose skeleton for the adsorption of cations (e.g., Cu(II), Pb(II), Hg(II)) [24,25]. Jahan, K et al. and Yang, Z et al. reported the in-situ fabrication of poly(aromatic amine) on bacteria cellulose for effectively separating Cr(VI) from the aqueous solution via reduction and chelation [26,27]. Unfortunately, bacteria cellulose must be dispersed firstly to allow the ultimate interaction between cellulose and polymers [24,27]. This complicates the procedures and moreover weakens the mechanical strength of the final macroscopic product [28]. Moreover, though the batch adsorption performance of these adsorbents were proven to be fine, the dynamic adsorption using macroscopic adsorbent was satisfied to practically purify continuous-flow industrial wastewater, which was scarcely reported.

Here, we report a facile fabrication of bacteria cellulose uniformly coated with poly Schiff base. The pretreatment by sodium silicate was applied first to modify the bacteria cellulose to increase the mass transfer efficiency without breaking the macroscopic structure. As a result, the polymerization of Schiff base proceeded effectively within the body of bacteria cellulose to achieve a uniform coating of polymer. The macroscopic composite monolith exhibits attracting performance in adsorption of Cr(VI) and other typical pollutants in batch and dynamic adsorption tests.
