Improvement of oxygen-containing functional groups on olive stones activated carbon by ozone and nitric acid for heavy metals removal from aqueous phase

Abstract

Recently, modification of surface structure of activated carbons in order to improve their adsorption performance toward especial pollutants has gained great interest. Oxygen-containing functional groups have been devoted as the main responsible for heavy metal binding on the activated carbon surface; their introduction or enhancement needs specific modification and impregnation methods. In the present work, olive stones activated carbon (COSAC) undergoes surface modifications in gaseous phase using ozone (O3) and in liquid phase using nitric acid (HNO3). The activated carbon samples were characterized using N2 adsorption-desorption isotherm, SEM, pHpzc, FTIR, and Boehm titration. The activated carbon parent (COSAC) has a high surface area of 1194 m(2)/g and shows a predominantly microporous structure. Oxidation treatments with nitric acid and ozone show a decrease in both specific surface area and micropore volumes, whereas these acidic treatments have led to a fixation of high amount of surface oxygen functional groups, thus making the carbon surface more hydrophilic. Activated carbon samples were used as an adsorbent matrix for the removal of Co(II), Ni(II), and Cu(II) heavy metal ions from aqueous solutions. Adsorption isotherms were obtained at 30 °C, and the data are well fitted to the Redlich-Peterson and Langmuir equation. Results show that oxidized COSACs, especially COSAC(HNO3), are capable to remove more Co(II), Cu(II), and Ni(II) from aqueous solution. Nitric acid-oxidized olive stones activated carbon was tested in its ability to remove metal ions from binary systems and results show an important maximum adsorbed amount as compared to single systems.

Synthesis and Characterization of Natural Extracted Precursor Date Palm Fibre-Based Activated Carbon for Aluminum Removal by RSM Optimization

“…Processes 2019, 7, x; doi: FOR PEER REVIEW www.mdpi.com/journal/processes 13 surface like -OH and -COOH which is matched with FTIR analysis [52]. Moreover, the pH of the adsorbent can be changed to negative or positive charge.…”

“…The effect of pH on the surface charge can be clearly observed in Figure 8. This phenomenon might be attributed to ionization of oxygen comprising of functional groups on the surface like -OH and -COOH which is matched with FTIR analysis [52]. Moreover, the pH of the adsorbent can be changed to negative or positive charge.…”

Production and applications of activated carbons as adsorbents from olive stones

“…Another phosphoric acid (PA)-activated carbon [171] from olive stone also had a significant cadmium adsorption capacity of 51.1 mg/g and the surface area was 1194 m 2 /g at pH = 5. The uptake of cobalt, nickel and copper on activated carbons obtained by treating olive stones with PA and PA + O 3 (ozone) provided capacities in the range 10 to 17.9 mg/g, but treatment with PA + HNO 3 (nitric acid) increased the nickel and copper capacities to 20.5 and 34.2 mg/g, respectively, by creating more oxidised sites in the form of surface carboxylic acid hydrogen ions for exchange with the metal ions [163]. In this study, the high capacity-activated carbon had the lowest surface area, 173 m 2 /g, indicating the importance of surface functional groups on carbon for heavy metal ion adsorption-ion exchange.…”

Simultaneous adsorption behavior of heavy metals onto microporous olive stones activated carbon: analysis of metal interactions

“…The main chemical and physical characteristics of the used activated carbon (COSAC) were presented in detail in our previous works (Bohli and Ouederni 2016;Bohli et al 2015). Total surface area was determined using the Brunauer-Emmett-Teller (BET) equation.…”