Guidelines for selecting efficient lead ion adsorbents: an overview

Recently, significant attention has been given to the development of adsorbents for the removal of lead ion from wastewater due to its toxicity and persistence. This review compiles and assesses 143 adsorbents, all demonstrating high Pb retention capacity. To aid in practical selection, a guideline was developed based on the following primary metrics: (a) uptake capacity (500–2000 mg/g), (b) reusability (5–15 cycles with 80–90% removal efficiency), (c) activity for Pb ions in the presence of common ions in wastewater, and (d) activity for multiple pollutant types. Based on this framework, CuFe₂O₄–sepiolite emerged as an excellent Pb adsorbent, with an uptake capacity of 1285 mg/g, a treatment time of 90 min, reusability for 5 cycles with a final efficiency of 95%, a high anti-interference ability for Ca²⁺, Mg²⁺, K⁺, and Na⁺, and simple isolation from the treated solution via an external magnet. Similarly, chitosan and amino-modified hydrogel were also identified as practical adsorbents, with uptake capacities ranging from 930 to 990 mg/g, reusability over 3–15 cycles with final efficiencies of 87%, high anti-interference ability for wastewater ions like Ca²⁺, Mg²⁺, and K⁺, and activity for removing Cu²⁺ and Fe³⁺. While the focus is on lead ions, the proposed guide is adaptable for identifying practical adsorbents targeting other pollutants, including dyes, phenols, and pesticides. The current review contributes an organized evaluation framework that creates key performance indicators, introducing a broader, more flexible comparison than typically existed in the literature.

Graphical abstract