Biosorption Mechanism of Aqueous Pb²⁺, Cd²⁺, and Ni²⁺ Ions on Extracellular Polymeric Substances (EPS)

Abstract

Heavy metal pollution has been a focus with increasing attention, especially Pb2+, Cd2+, and Ni2+ in an aqueous environment. The adsorption capacity and mechanism of extracellular polymeric substances (EPS) from Agrobacterium tumefaciens F2 for three heavy metals were investigated in this study. The adsorption efficiency of 94.67%, 94.41%, and 77.95% were achieved for Pb2+, Cd2+, and Ni2+ adsorption on EPS, respectively. The experimental data of adsorption could be well fitted by Langmuir, Freundlich, Dubinin–Radushkevich isotherm models, and pseudo-second-order kinetic model. Model parameters analysis demonstrated the great adsorption efficiency of EPS, especially for Pb2+, and chemisorption was the rate-limiting step during the adsorption process. The functional groups of C=O of carboxyl and C-O-C from sugar derivatives in EPS played the major role in the adsorption process judged by FTIR. In addition, 3D-EEM spectra indicated that tyrosine also assisted EPS adsorption for three heavy metals. But EPS from strain F2 used the almost identical adsorption mechanism for three kinds of divalent ions of heavy metals, so the adsorption efficiency difference of Pb2+, Cd2+, and Ni2+ on EPS could be correlated to the inherent characteristics of each heavy metal. This study gave the evidence that EPS has a great application potential as a bioadsorbent in the treatment of heavy metals pollution.

Agricultural waste of sugarcane bagasse as efficient adsorbent for lead and nickel removal from untreated wastewater: Biosorption, equilibrium isotherms, kinetics and desorption studies

“…The presence of heavy metals in the environment is a serious problem to be addressed in the world today due to their high toxicity, mobility in the environment and non-biodegradability [ 1 , 2 ]. Heavy metals which originates from the mining, electroplating, refinery and other industrial wastewater can cause potential damage to the ecosystem, human and animal health even at low concentration [ [3] , [4] , [5] ].…”

“…Lead which exist in several oxidation states (0, +1, +2 and +4), is known for its toxicity and environmental impact. It can be accumulated and adsorbed by the body through inhalation, ingestion, skin contact and transfer through the placenta [ 1 , 3 ]. Long-term exposure of lead to children, not only impacts their biological systems, but also has long-term effects, such as damage to central nervous system and chronic respiratory diseases [ [8] , [9] , [10] ].…”

Assessment of resistance and biosorption ability of Lactobacillus paracasei to remove lead and cadmium from aqueous solution

“…In addition to functional groups, extracellular polymeric substances (EPS) comprising protein and carbohydrate assist the bacterial species in metal resistance and absorption (Shameer, 2016). Besides, the divalent metal cations such as Pb (II) and Cd (II) tend EPS because of their small radius, which eventually decreased in the environment (Cui et al, 2020). In this regard, evaluated Lactobacillus acidophilus ATCC 4356 for Cd (II) and Pb (II) removal and elucidated their higher and prompt accumulation potential, which was consistent with the results of the current study.…”

Flocculation Efficiency and Mechanism of Carbamazepine by Microbial Flocculant Extracted from Klebsiella pneumoniae J1

“…There are numerous chemical groups (e.g. hydroxyl, carboxyl, and amino) in MFX, which allow MFX to have good combining capacity with pollutants and have good flocculation efficiency [ 12 – 15 ]. In addition to the removal of turbidity of wastewater, it has been proved that MFX can treat wastewaters that contain heavy metals [ 16 – 18 ] and antibiotics [ 19 – 21 ].…”