A template synthesized strategy on bentonite-doped lignin hydrogel spheres for organic dyes removal

A super-adsorbent bentonite-doped lignin hydrogel spheres (LHS-BT) were synthesized in 2 min via a simple template method to remove cationic dyes in wastewater. In this process, acrylic acid (AA) and 2-acrylamido-2methyl-propanesulfonic acid (AMPS) are grafted onto lignosulfonate through free radical reaction to construct polymer cross-linking network and enhance the adsorption capacity of lignin. Moreover, polyethersulfone was designed as a template to protect the internal crosslinking and maintain the spherical shape. Then, the template shell was ingeniously removed through heat shrinkage. The shell separation and drying process was completed in one step, reducing the post-processing process. A series of characterization methods were used to evaluate the structural characteristics of LHS-BT. The influences of dye concentration, initial pH value, temperature and contact time on adsorption procedure were systematically studied. The adsorption kinetics and equilibrium adsorption isotherms are in accordance with the pseudo-second-order kinetic model and Langmuir isotherm model, respectively. Adsorption experiments showed that LHS-BT have ultra-high adsorption capacity (2541.76 mg/g for malachite green, 1284.46 mg/g for methylene blue and 1047.72 mg/g for rhodamine B) and faster adsorption rate within 85 min. Additionally, LHS-BT exhibited excellent recyclability without significant efficiency loss for at least five cycles. The mechanism of dyes molecular capture onto LHS-BT might be principally ascribed to electrostatic attraction, 7C -7C interaction and hydrogen bonding. Thus, LHS-BT exhibits great potential for used in efficient, environmental, and economical wastewater remediation. Lastly, it is proved that LHS-BT is suitable for adsorption column to quickly purify wastewater containing dyes.

Automated summary

A super-adsorbent bentonite-doped lignin hydrogel spheres (LHS-BT) were synthesized for the removal of cationic dyes in wastewater. LHS-BT exhibited ultra-high adsorption capacity, fast adsorption rate, excellent recyclability, and multiple adsorption mechanisms. It has great potential for application in efficient and environmentally friendly wastewater remediation.