Removal Efficiencies of Manganese and Iron Using Pristine and Phosphoric Acid Pre-Treated Biochars Made from Banana Peels

Abstract

The purpose of this study was to compare the removal efficiencies of manganese (Mn) and iron (Fe) using pristine banana peel biochar (BPB) and phosphoric acid pre-treated biochars (PBPB) derived from banana peels. The removal efficiencies of Mn and Fe were investigated under different adsorbent dosages (0.4–2 g L−1), temperatures (15–45 °C), and ionic strengths (0–0.1 M), and were directly correlated to the differences in physicochemical properties of BPB and PBPB, to identify the removal mechanisms of heavy metals by adsorption processes. The removal of Mn by PBPB obeyed the Freundlich isotherm model while the removal of Mn and Fe by BPB followed the Langmuir isotherm model. However, the removal of Fe by PBPB followed both Freundlich and Langmuir isotherm models. The removal efficiencies of Mn and Fe by BPB and PBPB increased with increasing temperatures and decreased with increasing ionic strengths. PBPB more effectively removed Mn and Fe compared to BPB due to its higher content of oxygen-containing functional groups (O/C ratio of PBPB = 0.45; O/C ratio of BPB = 0.01), higher surface area (PBPB = 27.41 m2 g−1; BPB = 11.32 m2 g−1), and slightly greater pore volume (PBPB = 0.03 cm3 g−1; BPB = 0.027 cm3 g−1). These observations clearly show that phosphoric acid pre-treatment can improve the physicochemical properties of biochar prepared from banana peels, which is closely related to the removal of heavy metals by adsorption processes.

Adsorption Characteristics of Phosphate Ions by Pristine, CaCl2 and FeCl3-Activated Biochars Originated from Tangerine Peels

“…A similar result was previously observed for the removal of the pharmaceuticals with NaOH-activated biochars [48]. The adsorption affinities of PO 4 3− to the TB, CTB, and FTB were evaluated using the n values (dimensionless adsorption intensity) of the Freundlich isotherm model: (i) n > 1.0 (favorable), (ii) n = 1.0 (linear), and (iii) n < 1.0 (unfavorable) [49]. The adsorption of PO 4 3− by TB (n value = 0.766) was unfavorable, whereas the adsorptions of PO 4 3− by CTB (n value = 1.523) and FTB (n value = 7.530) were favorable.…”

Effects of NaOH Activation on Adsorptive Removal of Herbicides by Biochars Prepared from Ground Coffee Residues

“…Langmuir Freundlich The adsorption affinities of herbicides to the GCRB and GCRB-N were estimated using the n values and the R L values, respectively. The n values (dimensionless) of the Freundlich model using the GCRB were used to examine the adsorption affinity of the herbicides under the batch experiments: (i) n > 1.0 (favorable), (ii) n = 1.0 (linear), and (iii) n < 1.0 (unfavorable) [36]. The n values of ALA (1.15), DIU(1.10), and SIM (1.11) were favorable.…”

Enhanced Adsorptive Removal of Dyes Using Mandarin Peel Biochars via Chemical Activation with NH4Cl and ZnCl2

“…All adsorption experiments were repeated three times to minimize errors. The amount of MO and FG solution adsorbed per unit of mass adsorbent, Q t (mg/g), was calculated using the following equation [29]:…”

“…All mandarin peel biochars well fitted with the multilayer adsorption characteristics of the Freundlich isotherm model [44] than those of the Langmuir isotherm model, which was monolayer adsorption for MO and FG [45]. The n values (the dimensionless adsorption intensity) of the pristine and chemically activated mandarin peel biochars were used to evaluate the adsorption affinity toward MO and FG using the Freundlich isotherm model: (i) n > 1 (favorable), (ii) n = 1 (linear), and (iii) n < 1 (unfavorable) [29]. The adsorption of MO by M-biochar (n = 4.71), MN-biochar (n = 1.81), and MZ-biochar (n = 1.68), and the adsorption of FG by MZ-biochar (n = 1.38) was favorable.…”