Adsorptive removal of nitrate from synthetic and commercially available bottled water samples using De-Acidite FF-IP resin

Modified Hazelnut Shells as a Novel Adsorbent for the Removal of Nitrate from Wastewater

The aim of the study was to prepare a novel adsorbent by chemical modification of hazelnut shells and evaluate its potential for the nitrate removal from model solutions and real wastewater. The characterization of the novel adsorbent, i.e., modified hazelnut shell (MHS) was performed. The adsorbent characterization included the analysis of elemental composition and the surface characteristics analysis by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). The adsorption experiments (batch technique) were performed to investigate the effects of adsorbent concentration, contact time, initial nitrate concentration, and solution pH. The nitrate removal efficiency increased with the increase in MHS concentration and decreased with the initial nitrate concentration. MHS was found to be effective in nitrate removal over a wide pH range (from 2 to 10), and the highest amount of nitrate adsorbed was 25.79 mg g−1 in a model nitrate solution. Depending on the aqueous medium (model solutions or real wastewater samples), it was shown that both Langmuir and Freundlich adsorption isotherm models can be used to interpret the adsorption process. It was found that the kinetics are well described by a pseudo-second order model and the nitrate adsorption process can be controlled by chemisorption. The intraparticle diffusion model has been used to identify an adsorption-controlled process by diffusion mechanisms. Adsorption/desorption experiments in column confirmed that MHS could be successfully used in multiple cycles (at least three), indicating the potential of MHS as an alternative to costly commercial adsorbents for the removal of nitrates from wastewater.

Modified Grape Seeds: A Promising Alternative for Nitrate Removal from Water

The aim of this work was to investigate grape seeds as a potential adsorbent for nitrate removal from water. Grape seeds were modified by quaternization and the applicability of the modified grape seeds (MGS) was evaluated in batch adsorption experiments. Fixed bed adsorption and regeneration studies were carried out to determine the regeneration capacity of MGS. The maximum adsorption capacity of 25.626 mg g⁻¹ at native pH (6.3) for nitrate removal by MSG was comparable to that of the commercial anion exchange resin Relite A490 under similar conditions. The percent removal of nitrate from model nitrate solution was 86.47% and 93.25% for MGS, and Relite A490, respectively, and in synthetic wastewater 57.54% and 78.37%. Analysis of the batch adsorption data using isotherm models revealed that the Freundlich model provided a better fit to the data obtained than the Langmuir model, indicating multilayer adsorption. In kinetic terms, the results showed that the adsorption followed the pseudo-first order model. By investigating the adsorption mechanism, the results suggest that the intraparticle diffusion model was not the only process controlling the adsorption of nitrate on MGS. In column experiments (adsorption/desorption studies), three adsorption cycles were tested with minimal decrease in adsorption capacities, implying that this alternative adsorbent can be successfully regenerated and reused.

Modified biogas residues as an eco-friendly and easily-recoverable biosorbent for nitrate and phosphate removals from surface water

Effective managements of organic solid waste and surface water eutrophication can reuse/reduce solid waste resources, and ensure surface water safety. Herein, an easily-recoverable amine-functionalized biosorbent was developed from biogas residue (BR-N) for nitrate and phosphate removals from surface water. Physicochemical characteristics revealed that BR-N has a cross-staggered structure with abundant quaternary-amine groups to enhance the diffusion and electrostatic attraction of nitrate/phosphate. In batch studies, nitrate/phosphate could be effectively removed by the BR-N within a wide pH range of 5.0-9.0, and the maximum adsorption capacities of BR-N were 64.12 mg/g for nitrate and 34.40 mg P/g for phosphate. After continuous 8 cycles of adsorption-desorption, BR-N still exhibited >82% adsorption capacity for nitrate/phosphate removals, implying the high chemical stability and reusability for water treatment. Whereafter, BR-N has real application prospect in water treatment, which could effectively treat ˜380, ˜260 and ˜760 bed volumes (BV) of three actual eutrophic surface water to satisfy the surface water standard of China (GB3838-2002). The cost of BR-N was 2.89 $/kg evaluated by energy-economy assessment, indicating the low-cost production of biogas residue-based adsorbent for treating eutrophic surface water. Overall, this study provides a new idea for high-value utilization of organic solid waste and purification of eutrophic water.