Abstract
Ammonium (NH4+) is a main constituent of landfill leachates (50–2200 mg L−1) which has to be removed prior to indirect (<200 mg L−1) or direct discharge (<10 mg L−1) during landfill operation and aftercare, i.e., for more than 100 years after the end of waste disposal. In this study, lab-scale experiments regarding the sorption of NH4+ from landfill leachates using natural and modified clinoptilolite (Ca0.5,Na,K)6(Al6Si30)O72·20H2O) were conducted to assess the applicability of the innovative ion exchanger loop stripping (ILS) process for ammonium recovery. Samples of 20 g clinoptilolite after different pre-treatments (Ca loading, Na loading, natural loading) were shaken with 500 mL of each leachate from ten Austrian landfills (75 mg L−1 < c(NH4+) < 2805 mg L−1; 7.7 < pH < 8.7) for 24 h. Between 13% and 61% of the dissolved NH4+ was adsorbed to the clinoptilolite, which remained stable during the experiment. In summary, our study indicates that the ILS process is highly promising with respect to NH4+ recovery from landfill leachates, but further research is needed to reach threshold values for direct discharge.
Highlights
Ammonium (NH4 + ) is a main constituent of leachates from municipal solid waste (MSW) landfills (50–2200 mg L−1 ) [1]
We investigated the applicability of a natural zeolite from Slovakia for NH4 + removal from a wide range of different Austrian landfill leachates, which has not been presented elsewhere
A comparison of the chemical composition of the used clinoptilolites [24,30] shows that our zeolite has a higher K/Ca ratio which suggests that the lower average charge of the initially present cations allows for an easier exchange against NH4 +
Summary
Ammonium (NH4 + ) is a main constituent of leachates from municipal solid waste (MSW) landfills (50–2200 mg L−1 ) [1]. It is formed in the landfill from MSW The MSW which was landfilled prior to 2004 still releases 1.4 billion liters of leachate per year [6], which corresponds to 1134 ta−1 NH4 + assuming an NH4 + concentration of 800 mg L−1. NH4 + concentrations in leachate decrease [10], but residual
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