Abstract
The search for safer and sustainable management of animal manure is a global and topical challenge, in particular for the reduction of nitrogen (N) content. The use of natural adsorbents as zeolite-rich tuffs is recognized as a valid method to recover N, in the form of ammonium (NH4+), from animal manure. While the scientific literature is rich in studies performed on synthetic solutions and using clinoptilolite zeolites as adsorbent, it lacks information concerning adsorption in real liquid manure and using other types of zeolite-rich tuffs (e.g., chabazite). This work aims at exploring the NH4+ adsorption process from raw liquid swine manure, using a chabazite-rich zeolite tuff as adsorbent. The effects of temperature, contact time, and grain size have been assessed. Isotherms, kinetic models, and thermodynamic parameters have been investigated. Harkins-Jura isotherm correlates well with the observed data, in accordance with the formation of an adsorption multilayer. Kinetic data have been explained by intraparticle diffusion and pseudo-second-order models. In conclusion, the natural chabazite tuff has proven to be a valid material for NH4+ adsorption from raw liquid swine manure. In particular, to reach the highest adsorption capacities and adsorption rates, it is recommended to use it at a fine particle size and with dosages < 6 %.
Highlights
The intensification of agricultural activities to meet the increasing demand for food and agricultural products is leading to rapid soil degradation and severe environmental problems like GHG emissions and water pollution
We present a series of experiments in which we followed a similar protocol to characterize the isotherms, kinetics, and thermodynamics of NH4 + adsorption using a chabazite zeolite-rich tuffs (ZRT) in real animal liquid manure
The evaluation of qe is important in kinetic analyzes to test the validity of the kinetic models applied [37], we have considered that a “near-equilibrium” condition was achieved at 420 min from the beginning of the experiment
Summary
The intensification of agricultural activities to meet the increasing demand for food and agricultural products is leading to rapid soil degradation and severe environmental problems like GHG emissions and water pollution. The Food and Agriculture Organization of the United Nations (FAO) has declared that “to satisfy the expected food and feed demand, it will require a substantial increase of global food production of 70 percent by 2050, involving an additional quantity of nearly 1 billion tons of cereals and 200 million tons of meat” [1]. The need to improve fertilizer use efficiency (FUE) represents one of the major challenges for the upcoming years and it is essential for achieving more sustainable agriculture. Another global challenge that we are forced to face in the immediate future is the increasing demand for meat, which is rising according to the economic growth of countries like South America, India, and China. As a direct consequence of increased meat demand, large amounts of zootechnical
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