Zeolite Cotton in Tube: A Simple Robust Household Water Treatment Filter for Heavy Metal Removal

Abstract

It is challenging to develop a low-cost household water treatment (HWT) that simultaneously deliver an effective and robust way for safe and reliable water supply. Here, we report a simple flow-through filter made by zeolite-cotton packing in a tube (ZCT) as low-cost HWT device to remove heavy metal ions from contaminated water. The zeolite-cotton is fabricated by an on-site template-free growth route that tightly binds mesoporous single-crystal chabazite zeolite onto the surface of cotton fibers. As a result, the ZCT set-up with optimized diameter achieves both high adsorption efficiency, proper flow rate, reliable supply and strong stability at the same time. After flowed through the set up packed with 10 g of zeolite-cotton, 65 mL 1000 ppm Cu²⁺ solution was purified down to its safety limit (<1 ppm). Notably, their efficiency remains unaltered when filtering several ions simultaneously. In a simulated purification process, 8 L of water contaminated by Cu²⁺, Cd²⁺ and Pb²⁺ could be transformed into drinking water and it enables the removal of heavy metals to concentrations of below 5 ppb (μg L^-1). We also show that the ZCT can be used for disinfection by introducing Ag-exchanged zeolite-cotton without contaminating the water with Ag ions (<0.05 ppm).

Figure 1

Characterization of ZC (a) XRD patterns. (b) TG analysis of ZC and cotton only. (c,d) SEM images of ZC, hemi-spherical like particle is CHA and plate like particle is FAU, indicating that majority of zeolite is indexed to CHA.

Figure 2

The set up of HWT filter ZCT and its application procedure to collect drinking water.

Figure 3

Comparison of granular zeolite, powder zeolite, impregnated zeolite and ZC. (a) Schematic of these four kinds of zeolite packing in the tube. (b) Cu²⁺ remaining concentration and removal efficiency of four zeolite and the optical images of the collected water (inset). (c) Residual weight of zeolite on impregnated zeolite and ZC after ultrasonic clean. (d) Cu²⁺ static adsorption performance of impregnated zeolite and ZC before and after hand-washing.

Figure 4

Performance of four ZCT with different tube diameters (20 mm, 15 mm, 10 mm and 5 mm). (a) Schematic of 10 g ZC packing in those four tubes. (b) Volume of safety water obtained by four tubes, starting concentration: Cu²⁺ = 1000 ppm. (c) The volume of the safety water purified by four tubes within 2 h. (d) Remaining concentration for long-term flowing with three ions (Cu²⁺, Cd²⁺ and Pb²⁺) with a starting concentration: Cu²⁺ = 4.29 ppm, Cd²⁺ = 3.12 ppm and Pb²⁺ = 14.19 ppm. The flowed through water is below the safety limit for drinking water.

Figure 5

(a) The Schematic of dual-bed HWT filter used for anti-bacteria. (b) Number of E. Coli colony and remained Ag⁺ concentration after filtered through the beds of 10 g ZC, 5 g AgZC and 5 g AgZC + 5 g ZC, respectively.