A Review of Adsorbents for Heavy Metal Decontamination: Growing Approach to Wastewater Treatment

Abstract

Heavy metal is released from many industries into water. Before the industrial wastewater is discharged, the contamination level should be reduced to meet the recommended level as prescribed by the local laws of a country. They may be poisonous or cancerous in origin. Their presence does not only damage people, but also animals and vegetation because of their mobility, toxicity, and non-biodegradability into aquatic ecosystems. The review comprehensively discusses the progress made by various adsorbents such as natural materials, synthetic, agricultural, biopolymers, and commercial for extraction of the metal ions such as Ni2+, Cu2+, Pb2+, Cd2+, As2+ and Zn2+ along with their adsorption mechanisms. The adsorption isotherm indicates the relation between the amount adsorbed by the adsorbent and the concentration. The Freundlich isotherm explains the effective physical adsorption of the solute particle from the solution on the adsorbent and Langmuir isotherm gives an idea about the effect of various factors on the adsorption process. The adsorption kinetics data provide valuable insights into the reaction pathways, the mechanism of the sorption reaction, and solute uptake. The pseudo-first-order and pseudo-second-order models were applied to describe the sorption kinetics. The presented information can be used for the development of bio-based water treatment strategies.

Preparation of Magnetic MIL-68(Ga) Metal–Organic Framework and Heavy Metal Ion Removal Application

“…So far, precipitation [ 6 , 7 ], membrane process [ 8 , 9 ], ion exchange [ 10 , 11 ] and adsorption [ 12 , 13 ] techniques have been demonstrated to effectively eliminate heavy metal ions from contaminated water. Among them, adsorption is a promising and effective method for practical use due to its high efficiency, simple design and easy operation [ 14 , 15 , 16 , 17 ]. Various adsorbents, such as carbon materials (activated carbon, nanotubes), polymers, metallic and metal compounds (nanoparticles, metal–organic frameworks, and magnetic materials), and minerals (silica, zeolites, and clays) have been developed to remove heavy metal ions in water [ 18 , 19 , 20 , 21 ].…”

Influences of Biochar on Bioremediation/Phytoremediation Potential of Metal-Contaminated Soils

“…Because ionic metals and metalloids can occur in both anionic and cationic aspects, their behavior will be influenced by interactions with anionic and cationic charges of the biochar surface ( Fijałkowska et al, 2021 ). When combined with topsoil, biochar with negative charges can strongly adsorb positive components (e.g., Cd 2+ and Pb 2+ ), whereas biochar with cationic charges can maintain anionic metal(loid)s (e.g., arsenite and arsenate) ( Gupta et al, 2021 ). Adsorption mechanism, surface (co)precipitation, and surface complexation with active functional moieties are the major mechanisms for the immobilization of cationic metals (including Pb 2+ ) and metalloids through biochar ( Gupta et al, 2021 ).…”

“…When combined with topsoil, biochar with negative charges can strongly adsorb positive components (e.g., Cd 2+ and Pb 2+ ), whereas biochar with cationic charges can maintain anionic metal(loid)s (e.g., arsenite and arsenate) ( Gupta et al, 2021 ). Adsorption mechanism, surface (co)precipitation, and surface complexation with active functional moieties are the major mechanisms for the immobilization of cationic metals (including Pb 2+ ) and metalloids through biochar ( Gupta et al, 2021 ). Thus, the biochar-stimulated improvements in soils, including increased soil pH, can reduce the bioavailability of cationic metals and metalloids even further.…”

“…Since the physical and chemical attributes of biochar depend on the raw material type and pyrolysis circumstances (e.g., temperature and frequency of temperature rise), it is essential to recognize appropriate raw materials for biochar fabrication that have the efficiency to remediate various metals and metalloids in specific soils ( Akhil et al, 2021 ). Anionic metalloids, including Cr, Se, and As, are frequently found as dominant species in soils with alkaline pH compared to cationic metalloids that are poorly adsorbed by negatively charged soil ( Gupta et al, 2021 ).…”

Biochemical Fulvic Acid Modification for Phosphate Crystal Inhibition in Water and Fertilizer Integration

“…Among the various modifiers, AA is chosen because it is easy to polymerize and able to provide the necessary carboxylic groups [ 38 , 39 , 40 , 41 ]. Potassium peroxydisulfate is a quite effective initiator in grafting copolymerization [ 42 , 43 , 44 ]. So, in the paper, the grafting copolymerization experiments were designed for improving the chelating and adsorption capacity of BFA, in which AA was used as modifier and potassium peroxydisulfate as initiator.…”