Over the past few decades, researchers have established artificial enzymes as highly stable and low-cost alternatives to natural enzymes in a wide range of applications. A variety of materials including cyclodextrins, metal complexes, porphyrins, polymers, dendrimers and biomolecules have been extensively explored to mimic the structures and functions of naturally occurring enzymes. Recently, some nanomaterials have been found to exhibit unexpected enzyme-like activities, and great advances have been made in this area due to the tremendous progress in nano-research and the unique characteristics of nanomaterials. To highlight the progress in the field of nanomaterial-based artificial enzymes (nanozymes), this review discusses various nanomaterials that have been explored to mimic different kinds of enzymes. We cover their kinetics, mechanisms and applications in numerous fields, from biosensing and immunoassays, to stem cell growth and pollutant removal. We also summarize several approaches to tune the activities of nanozymes. Finally, we make comparisons between nanozymes and other catalytic materials (other artificial enzymes, natural enzymes, organic catalysts and nanomaterial-based catalysts) and address the current challenges and future directions (302 references).

Nanomaterials with enzyme-like characteristics (nanozymes): next-generation artificial enzymes

Adsorption of methylene blue on low-cost adsorbents: A review

A review on modification methods to cellulose-based adsorbents to improve adsorption capacity

Adsorptive removal and photocatalytic degradation of organic pollutants using metal oxides and their composites: A comprehensive review

Industries generating wastewater with elevated concentrations of pollutants (e.g. metals, dyes, phenolic compounds, anions, etc.) need specialized atreatment systems. Adsorption is one of the most extensively applied techniques for the removal of pollutants from the industrial effluents. The prominent and emerging trend of subjecting biosorbent in the adsorption technology is mainly because of their natural existence, abundance, renewable, biodegradable and economic features. The adsorption isotherm equations used to describe the experimental data and the thermodynamic assumptions of the models often provide some insight into the sorption mechanism, the surface properties and affinity of the biosorbent. This paper presents a state of the art on the review of adsorption isotherm models in an exhaustive manner on the basis of two, three, four and five parameters respectively. Focuses on the various sources of agricultural byproducts as biosorbents and describes on the potential applications of different adsorption isotherm models for the evaluation of the wastewater pollutants biosorption. It is evident from the literature survey that various adsorption isotherm models have been considered under study by the researchers but mostly two and three parameter isotherm model were best fitted the equilibrium data. This paper reviews the adsorption isotherm models on the basis of parameters that can be applied for exploring a novel biosorbents.

Relevance of isotherm models in biosorption of pollutants by agricultural byproducts

Removal of basic (Methylene Blue) and acid (Egacid Orange) dyes from waters by sorption on chemically treated wood shavings.

Cerium dioxide as a new reactive sorbent for fast degradation of parathion methyl and some other organophosphates

Removal of metal ions from aqueous solutions by sorption onto untreated low-rank coal (oxihumolite)

Iron humate (IH) produced as a waste by-product during the industrial manufacture of humic substances from young brown coal was tested as a new cost-effective sorbent for the removal of inorganic arsenic from waters. Its removal efficiency was compared with that of two other non-conventional sorbents – magnetite and oxihumolite (weathered brown coal). Magnetite and IH have been found to be effective in removing both forms of inorganic arsenic (arsenite and arsenate) from aqueous solutions. The removal efficiency was only slightly affected by the pH value in an acidic to neutral working pH range of the sorbents. It was found that the arsenic removal with the aid of IH is a rather slow process requiring several days to attain equilibrium; however it is much more rapid (with equilibrating times not exceeding four hours) with magnetite and oxihumolite. The examined sorbents were successfully applied to the removal of arsenic from real groundwater heavily contaminated by arsenic leaching from mine tailings. The low-cost sorbents in combination with the commonly employed oxidation/precipitation processes could enhance the overall efficiency of arsenic removal from contaminated effluents by approximately 10-30 %.

Vera Pilarova

Papers

Removal of basic (Methylene Blue) and acid (Egacid Orange) dyes from waters by sorption on chemically treated wood shavings.

Cerium dioxide as a new reactive sorbent for fast degradation of parathion methyl and some other organophosphates

Removal of metal ions from aqueous solutions by sorption onto untreated low-rank coal (oxihumolite)

Comparison of some non-conventional sorbents for the removal of arsenic from waters