Novel Regenerative Hybrid Composite Adsorbent with Improved Removal Capacity for Lead Ions in Water

Abstract

Lead is one of the most toxic heavy metals in water systems which poses critical effects on human health. To meet the 10 ppb limit in drinking water recommended by the World Health Organization, a highly efficient adsorbent with extremely lowconcentration removal capability is needed. Herein, we develop a hybrid composite adsorbent βCD-AC-CaBent that is composed of βcyclodextrin, activated carbon, and calcium-enhanced bentonite clay via a chemical method. The enlarged surface area of 41.56 m 2 /g and increased negative charge of −45.04 mV greatly improved the attraction of Pb 2+ to the porous surface, while the large amount of active Ca 2+ sites further increased the ion-exchange capacity. By varying the initial Pb 2+ concentration, pH value, and contact time, the adsorbent's lead removal capacity was studied in batch tests, whose results were fitted with pseudo-first-order, pseudo-second-order, and intraparticle diffusion kinetic models and Langmuir/Freundlich isotherms. In parallel, breakthrough curves with Pb 2+ concentrations from 12 to 100 mg L −1 , flow rates from 10 to 100 mL min −1 , and bed heights from 1.2 to 3.2 cm were obtained in a continuous fixed-bed column, which were fitted with Thomas, Yoon−Nelson, and Bohart−Adam models, respectively. The hybrid adsorbent displayed excellent removal efficiency after regeneration, which indicates its promising potential in sustainable applications. The results showed that the capacities of 174.5 mg g −1 at a dosage of 1.0 g L −1 and 434.78 mg g −1 at a dosage of 0.25 g L −1 were, respectively, achieved within about 60 min, which are higher than those of pure bentonite and most of the commercial adsorbents. In column tests, an adsorption capacity of up to 39.78 mg g −1 was obtained. More importantly, the removal uptake capacity of 10.5 mg g −1 at 0.5 ppm Pb 2+ concentration and 4.3 mg g −1 at 50 ppb Pb 2+ concentration was achieved upon treatment of 75 L of water. As high as 100% Pb 2+ ions were removed at the beginning and still 70% Pb 2+ ions were removed upon saturation in industrial wastewater. The current results suggest a new hybrid adsorbent that can deliver a high lead removal capacity in water under differential conditions especially with extremely low-ion concentrations.

A carbon dot-based clay nanocomposite for efficient heavy metal removal

“…To test the regeneration capacity of the B–CDs material via Pb( ii ) removal, the reusability of the used adsorbent was investigated by performing five successive adsorption–desorption cycles; a procedure was carried out by desorbing the lead ions from B–CDs using acid treatment. 35 The clay was centrifuged in 0.1 M nitric acid for 30 min and then used for the adsorption study as done initially. This cycle was repeated four times, and the removal efficiency percentage of each cycle has been calculated and is displayed in Fig.…”

Selective Removal of Iron, Lead, and Copper Metal Ions from Industrial Wastewater by a Novel Cross-Linked Carbazole-Piperazine Copolymer

“…When the data show several linear plots, it implies that adsorption was caused by more than one mechanism. As a result, these rate-determining processes may be split into multiple linear curve segments throughout time, each having control over the entire process [47,48]. The discovery of the rate-limiting step provides new insights into the mechanism of the adsorption process.…”