Performance of surfactant‐modified activated carbon prepared from dates wastes for nitrate removal from aqueous solutions

Abstract

New material (AC‐CTABr) was successfully prepared from chemical activation of dates wastes (AC), followed by cationic surfactant modification and was used to enhance nitrate removal from aqueous solutions. Brunauer, Emmett and Teller (BET) analysis revealed good binding of quaternary ammonium groups on the surface (1407 m2/g for the AC and 569 m2/g for the AC‐CTABr). Batch experiments were conducted to examine the effect of contact time, solution pH, adsorbent dose, and initial concentration of nitrate. Preliminary results showed an improvement of nitrate removal from 14% to 60% for the AC and the AC‐CTABr, respectively. Also, the adsorption kinetic was very fast; the equilibrium was achieved within the first 5 min of contact time between the adsorbents and the nitrate solution. Application of several isotherm models has shown that Langmuir and Freundlich models described well the experimental data with a maximum adsorption capacity of 83.33 mg/g. Three simplified kinetic models were tested to investigate the adsorption mechanism. The pseudo‐second order model was found to describe adequately the experimental kinetic data. Results showed that the new adsorbent material is a suitable adsorbent for nitrate removal. © 2018 American Institute of Chemical Engineers Environ Prog, 38: S403–S411, 2019

Assessment of Surfactant Modified Activated Carbon for Improving Water Quality

“…Similarly, Allalou et al [28] recorded an increase in the specific nitrate uptake from 32 to 80 mg/g but decrease in percentage anion removed from 92% to 40% as the initial concentration increased from 100 to 600 mg/L. For a fixed mass of adsorbent, at low initial adsorbate concentration, active binding sites are under saturated but tend towards saturation as the initial concentration increases [28]. This will make the ratio of adsorbed concentration to initial concentration decreases as the initial adsorbate concentration increases [16].…”

“…For instance, Kakavandi et al [26] observed that at pH 7, 1.2 g/L adsorbent concentration, 20˚C, 200 rpm, Co (II) specific uptake by SDS modified activated carbon increased from 16.4 to 40.8 mg/g while the percentage cation removed decreased from 98.2% to 49% as the initial Co (II) concentration increased from 20 to 100 mg/L. Similarly, Allalou et al [28] recorded an increase in the specific nitrate uptake from 32 to 80 mg/g but decrease in percentage anion removed from 92% to 40% as the initial concentration increased from 100 to 600 mg/L. For a fixed mass of adsorbent, at low initial adsorbate concentration, active binding sites are under saturated but tend towards saturation as the initial concentration increases [28].…”

“…This usually increases the specific anions uptake by cationic modified activated carbon. However, excessive increase in the pH far below pH pzc reduced specific uptake of nitrate by CTAB modified activated carbon [28] and perchlorate by CTAC modified activated carbon [20] possibly due to repulsion between the protonated anions and positively charged amines groups on the cationic modified activated carbon [36].…”

“…This is due to pore blockage as the surfactant anchors its hydrophobic group onto the activated carbon via the micropores. Allalou et al [28] observed that a virgin activated carbon with initial BET specific surface of 1407 m 2 /g reduced to 569 m 2 /g after CTAB modification.…”

“…However, adsorption rate of such modified activated carbons has no definite pattern. Surfactant modification could increase adsorption rate [22], reduce rate [25] [29] or maintain rate [28] when compared to virgin activated carbons.…”