Efficient ammonia nitrogen removal from groundwater sources using natural Clinoptilolite: Multi-stage Series Micro-adsorption Columns

Ammonia nitrogen pollution in aqueous media is a challenging treatment, which poses significant health concerns to humans and degrades pristine water environments due to eutrophication. Clinoptilolite shows a highly selective adsorption capacity toward in situ treatment of ammonia nitrogen (NH4+-N) contaminated groundwater compared to other methods, as they can be easily injected, high ion exchange capacity, selectivity and compatibility with the natural environment. A Japanese natural Clinoptilolite with a particle size of 0.55 similar to 1.30 mm filled in a Multi-stage Series Micro-adsorption Columns was adopted to treat simulated groundwater containing NH4+-N at a concentration of about 10 ppm through exchange adsorption until the adsorption reached saturation. The final effluent NH4+-N concentration reached 1 +/- 0.20 L mg N/L, the treated water volume was 92.67 +/- 3.00 L, and the treatment time was 32.5 h. The saturated adsorption capacity was 12.76 +/- 0.25 mg-N/(g zeolite), and processing volume SV per unit time per unit volume reached 421.6 m3/m3<middle dot>d. Clinoptilolite was efficiently regenerated with a saturated NaCl solution when full of adsorption. Regenerate the saturated zeolite with a neutral NaCl-saturated solution. Effluent NH4+-N concentration reached a maximum of 4966 +/- 63.64 mg N/L. The regeneration recovery rate increased by more than 90% after 130 min. The saturated NaCl solution was very effective in regenerating the zeolite. The regenerant consumption was 1.875 +/- 0.18 L kg NaCl/(1L zeolite), and the amount of waste brine was 1.24 +/- 0.10 L (7.76 BV). Again, regenerated Clinoptilolite was used for NH4+-N removal. 193.28 +/- 6.21 water was treated within 63 h. The maximum adsorption capacity and SV were 15.56 +/- 0.34 mg-N/(g zeolite) and 460.19 m3/m3<middle dot>d. Clinoptilolite saturated with NH4+ was again regenerated. The recovery rate increased above 90% after 150 min. About 300.4 g NaCl was used to regenerate 90 g of Clinoptilolite, and the waste brine had about 10.3 BV. There was an accumulation of NH4+-N in brine in one column after another, and the maximum level could be 6000 mg N/L. The system is efficient, safe, cost-effective, has no secondary pollution, and is highly suitable for small-scale water supply systems and engineering applications.