Chitosan-Modified Biochars to Advance Research on Heavy Metal Ion Removal: Roles, Mechanism and Perspectives

Abstract

The chitosan-modified biochars BC-CS 1-1, BC-CS 2-1 and BC-CS 4-1 were subjected to the synthetic application of biochar from agriculture waste and chitosan for the adsorption of Cu(II), Cd(II), Zn(II), Co(II) and Pb(II) ions from aqueous media. The results displayed a heterogeneous, well-developed surface. Additionally, the surface functional groups carboxyl, hydroxyl and phenol, determining the sorption mechanism and confirming the thermal stability of the materials, were present. The sorption evaluation was carried out as a function of the sorbent dose, pH, phase contact time, initial concentration of the solution and temperature. The maximum value of qt for Pb(II)-BC-CS 4-1, 32.23 mg/g (C0 200 mg/L, mass 0.1 g, pH 5, 360 min), was identified. Nitric acid was applied for the sorbent regeneration with a yield of 99.13% for Pb(II)-BC-CS 2-1. The produced sorbents can be used for the decontamination of water by means of the cost-effective and high-performance method.

Recent trends and economic significance of modified/functionalized biochars for remediation of environmental pollutants

“…The most commonly used alkaline agents are sodium hydroxide (NaOH) and potassium hydroxide (KOH) 34 , 35 . Alkali activation of biochar using NaOH and KOH can enhance the surface basicity and O content while dissolving condensed organic matter (such as cellulose, and lignin) and ash to aid subsequent modification 36 . After alkaline activation, blocked pores are cleansed, causing higher porosity 24 .…”

Black Tea Waste as Green Adsorbent for Nitrate Removal from Aqueous Solutions

“…Due to the long drying time, physical regeneration methods such as water regeneration and heat regeneration are less effective, less stable, and therefore more costly. The adsorbent is frequently regenerated using straightforward chemical reagents such as acid, alkali, and salts, because the chemical regeneration method offers the advantages of high regeneration efficiency and low cost [ 29 , 42 ].…”

“…The values of the thermodynamic parameters of Gibbs free energy (∆G), change in enthalpy (∆H), and change in entropy (∆S) were calculated by using the Langmuir isotherm constant K L at different temperatures (Table 4). The following expression can be used to associate the Langmuir adsorption constant with the free energy of adsorption ∆G [31,42,43]:…”

“…where T is temperature (Kelvin), R is the gas constant (8.314 • 10 −3 kJ/mol•K), and K L is the equilibrium constant obtained from the Langmuir isotherm model. Enthalpy and entropy changes are also related to the Langmuir equilibrium constant by the following equation [3,10,42]:…”

Determination of the Ni(II) Ions Sorption Mechanism on Dowex PSR2 and Dowex PSR3 Ion Exchangers Based on Spectroscopic Studies

“…Using the formulae provided in [ 22 ], the thermodynamic parameters’ entropy change ΔS° (kJ/mol), free energy change ΔG° (kJ/mol), and enthalpy change ΔH° (kJ/mol) were calculated and interpreted.…”