2019 | Singapore | Haiyi Wang

Novel Hybrid Regeneration Process for Adsorbent used in Wastewater Treatment

Water issue adressed: Too dirty

Research on adsorbent has been intensively studied to remove pollutants from wastewater, and layered double hydroxide (LDH) has shown remarkable performance. However, regeneration of exhausted LDH, being the most difficult part of adsorption technology, is often overlooked. This project developed an innovative method, electrochemical (EC) regeneration, to regenerate LDH and adsorbed products. It has very low energy expenditure and can be done on-site with simple setup. It was discovered that LDH activated through calcination has a remarkable adsorption capacity which is 60 times than that of activated carbon. Capacity of LDH can be fully recovered for 6 cycles consecutively. This project successfully developed effective regeneration methods, thus turning wastewater and adsorbed products into resources again.

This is how I came up with the idea for this project:

Adsorbents can effectively remove soluble contaminants from wastewaters. However, it can create more waste as there is no effective way to clean and reuse adsorbed pollutants. Therefore, I aimed to develop ways to reuse the water, adsorbent and adsorbate thus making the adsorption technology more environmentally friendly and economically viable.

DOCUMENTATION

Novel Hybrid Regeneration Process for Adsorbent used in Wastewater Treatment A waste is not considered a resource as it is contaminated with other pollutants or has too low a concentration to be considered a resource. This project looks at a novel way of synthesizing a powerful adsorbent layered double hydroxide (LDH) to purify wastewater. It also develops an innovative method called electrochemical (EC) regeneration to regenerate the adsorbed products. An optimized voltage of -0.6V has been identified to repel the intercalated pollutants out of the interlayer of LDH without causing material degradation. It demonstrated a 185% boost in recovery rate compared to conventional desorption method. This environmentally friendly process can be operated on-site since little energy is consumed. A second method, calcination is optimized as activation and regeneration method. It was discovered that LDH activated at 400°C has a remarkable adsorption capacity of 418 mg/g for Congo Red which is 60 times than that of activated carbon. Fourier Transform Infrared (FTIR) showed that the “memory effect” of LDH is triggered which accounts for the drastic increase in capacity. Exhausted LDH was regenerated afterwards and it was found that 400°C is the most suitable temperature. The reusability of LDH was studied using 400°C calcination and recovery rate was above 95% up till the 6th cycle. It reduces capacity loss per cycle by 80%. SEM images and FTIR spectrum of LDH were obtained to study the degradation mechanism. Calcination is as an effective method to be employed in regenerating exhausted LDH. This project successfully develops effective regeneration methods, thus turning wastewater and adsorbed products into resources again.

CONTACT WATERTANK

Ania Andersch

Programme manager ania.andersch@siwi.org +46 8 121 360 59