A versatile alginate aerogel with spatially separated sorption sites for simultaneously and collaboratively scavenging Pb(II) and tetracycline in wastewater: Insight into behavior and mechanisms in the mixture system.

Alleviating combined pollution caused by heavy metals and antibiotics is of great significance for ecological sustainability and human health. It is still quite challenging to simultaneously and efficiently scavenge both pollutants due to their completely different physicochemical properties and the fierce competition between multi-pollutants faced by traditional adsorbents. In present work, a novel alginate-based aerogel microbead (GO/Fe-Ca-Alg) with specific sorption sites toward these two sorts of pollutants was fabricated via a 'multi-site coupling' strategy. It was found that multifarious sorption sites in the composite synergistically enhanced removal performance of Pb(II) and TC. The adsorption process of Pb(II) was better described by pseudo-second-order kinetics model (R = 0.968-0.989) and Langmuir isotherm model (R = 0.966-0.996). The maximum adsorption capacity of Pb(II) and TC in their individual systems was 268.04 and 1664.04 mg/g, respectively, superior to most reported sorption materials. Interestingly, in Pb(II)-TC binary system, Pb(II) capture was enhanced by co-existing TC and its adsorption capacity was positively correlated with concentration of co-existing TC, assigning to the formation of ternary complex (adsorbent-TC-Pb(II) or adsorbent-Pb(II)-TC). However, the removal of TC was enhanced with 10 mg/L Pb(II), and hindered with 20-80 mg/L Pb(II) because of the competition effect of Pb(II) and TC. Sequential adsorption as well as Zeta potential experiments were further performed to verify mutual interaction between Pb(II) and TC. More importantly, the as-designed material was applied in treatment of simulated aquaculture wastewater with removal rates above 80 %, showing its great potential for simultaneous and collaborative elimination of Pb(II) and TC in complex wastewater. This work provided unique insights into designing integrated adsorbents for wastewater bearing heavy metals and antibiotics.