Remediation of Acid Rock Drainage by Regenerable Natural Clinoptilolite

Abstract

Clinoptilolite is investigated as a possible regenerable sorbent for acid rock drainage based on its adsorption capacity for Zn, adsorption kinetics, effect of pH, and regeneration performance. Adsorption of Zn ions depends on the initial concentration and pH. Adsorption/Desorption of Zn reached 75% of capacity after 1-2 h. Desorption depended on pH, with an optimum range of 2.5 to 4.0. The rank of desorption effectiveness was EDTA>NaCl>NaNO 3 > NaOAc>NaHCO 3 >Na 2 CO 3 >NaOH>Ca(OH) 2 . For cyclic absorption/desorption, adsorption remained satisfactory for six to nine regenerations with EDTA and NaCl, respectively. The crystallinity and morphology of clinoptilolite remained intact following 10 regeneration cycles. Clinoptilolite appears to be promising for ARD leachate treatment, with significant potential advantages relative to current treatment systems.

Regeneration of natural zeolite polluted by lead and zinc in wastewater treatment systems

“…During the first three adsorption/desorption cycles the amount of metal adsorbed on the mineral was enhanced since the use of KCl enhanced the metal adsorption on zeolite. This finding agrees with previous research work [14]. Several reasons can account for this behaviour.…”

“…The most effective solution for zinc desorption was 1 M KCl and for lead it was 3 M KCl. Table 5 summarizes the desorption efficiencies reported in the literature for various minerals, metals and desorbing solutions [10,11,14,[51][52][53][54]. It is evident that the desorption efficiencies obtained in this study for lead and zinc were very high (>98.5%).…”

“…Cui et al [13] studied the adsorption/desorption of zinc on/from clinoptilolite in a laboratory slurry bubble column using NaCl as desorbent accomplishing a desorption efficiency of 56%. Li et al [14] investigated the desorption of Zn(II) from clinoptilolite and found that EDTA was the most effective desorbing medium followed by NaCl.…”

The effect of different extractants on lead desorption from a natural mineral

“…For this reason, 0.2 M EDTA complexing agent was mixed with a 0.01 M acetic buffer of pH value 3.0 in the ratio 1:1. The application of EDTA as complexing agent for the extraction of Cu 2+ -and Zn 2+ -ions from natural clinoptilolite was described and tested by Li et al [24]. Pb 2+ -ions have a low hydratation energy (-1481 kJ/mol) and high rate coefficient for water exchange (≈1 × 10 1 s −1 ), which means that there will be a high affinity to lose water molecules and interact with another ligand [25].…”

“…Not much data exit in the literature related to lead desorption from natural sorbents [21,23,24]. The aim of this study was to investigate the optimal purification solution for lead extraction from a mixture of mineral components.…”