Chromium Removal from Aqueous Solution Using Natural Clinoptilolite

Abstract

This work investigates the applicability of clinoptilolite, a natural zeolite, as a low-cost adsorbent for removing chromium from aqueous solutions using fixed bed studies. To improve its removal performance for the inorganic pollutant, the adsorbent is pretreated with NaCl to prepare it in the homoionic form of Na+ before undertaking ion exchange with Cr3+ in aqueous solution. This work also evaluates if treated effluents could meet the required effluent discharge standard set by legislation for the target pollutant. To sustain its cost-effectiveness for wastewater treatment, the spent adsorbent is regenerated with NaOH. It was found that the clinoptilolite treated with NaCl has a two-times higher Cr adsorption capacity (4.5 mg/g) than the as-received clinoptilolite (2.2 mg/g). Pretreatment of the clinoptilolite with NaCl enabled it to treat more bed volume (BV) (64 BV) at a breakthrough point of 0.5 mg/L of Cr concentration and achieve a longer breakthrough time (1500 min) for the first run, as compared to as-received clinoptilolite (32 BV; 250 min). This suggests that pretreatment of clinoptilolite with NaCl rendered it in the homoionic form of Na+. Although pretreated clinoptilolite could treat the Cr wastewater at an initial concentration of 10 mg/L, its treated effluents were still unable to meet the required Cr limit of less than 0.05 mg/L set by the US Environmental Protection Agency (EPA).

Fixed-Bed Studies of Landfill Leachate Treatment Using Chitosan-Coated Carbon Composite

“…The accuracy of the data was considered ideal, as indicated by the standard deviation of their removal being less than 1.0% [53]. A low standard deviation suggests that the results were consistent and reliable across the replicated experiments and indicates a high level of precision in the measurements.…”

High-Strength Organic–Inorganic Composites with Superior Thermal Insulation and Acoustic Attenuation

“…The hybrid nature of these PUC composites (0.9−1.2 g/ cm 3 ) contributes to their low densities, compared to OPC (1.5 g/cm 3 ). Despite the innately higher density of clinoptilolite (2−2.2 g/cm 3 ), 24,25 the low density of the PUC composites can be attributed to their porous structure and the presence of the organic components. The effect of porosity on the density is more pronounced at higher excess TDI contents (and lower clinoptilolite contents) owing to a lower solid loading and increased foaming.…”

Synthesis, characterization and analytical prospects of cellulose-derived nanoparticles of Ferric-oxide (Fe2O3/cellulose) and Copper-oxide (CuOx)

“…One of the most hazardous heavy metal contaminants is Chromium Cr(VI), which has been utilized extensively and on a massive scale in a number of sectors, including metal cleaning, dyes, leather, textiles, and plating. Cr(VI) is a transition metal, steel-gray, lustrous, stiff, and having brittle appearance [1][2][3][4]. Cr(VI) has a high degree of oxidation resistance even at high temperatures.…”

“…The Maximum Contaminant Limit (MCL) for chromium in drinking water is 0.05 mg/L, according to a 2013 report from the California Department of Public Health. The public health objective for Cr(VI) is 0.02 ppb; however the maximum contamination level is established at 10 ppb [4,5]. The quick removal of Cr(VI) ions from contaminated water has been focused from the last few decades and numerous techniques has been utilized such as electrochemical deposition, ion exchange, adsorption, biological methods, and membrane separation.…”