Abstract
Since adsorption is one of the best ammonium removal methods, great efforts have been made to identify new low-cost and efficient adsorbents from agricultural waste and by-products due to their abundant availability, low-cost and eco-friendly advantages, in addition to the possibility of recycling ammonium back into agricultural processes. In this study, a series of batch experiments were performed to detect new bio-adsorbents for ammonium ions removal. Among the materials tested, pomegranate peel powder showed a high affinity to adsorb ammonium ions and, furthermore, available information on ammonium adsorption by this biomaterial is still missing from the literature. First, pomegranate peel powder was characterized by the determination of different parameters such as zeta potential, iodine number, Fourier-transform infrared spectroscopy analysis, scanning electron microscopy, particle size distribution and porosity. Then, the impact of various parameters, such as pH, contact time, stirring speed, adsorbent dose and adsorbate concentration in the adsorption process, was investigated. The highest ammonium removal capacity was obtained at pH = 4 using 400 mg of pomegranate peel powder and a stirring speed of 150 rpm for an initial concentration of ammonium of 30 mg/L. The system (adsorbent, adsorbate and solution) reached equilibrium after 2 h and the data fit well with the Langmuir model with a maximum monolayer adsorption capacity of 6.18 mg/g, while kinetics were well described by the pseudo-second-order model. These results introduce pomegranate peel powder as a promising bio-adsorbent to remove and recover ammonium from aqueous solutions.
Highlights
Nitrogen compounds discharged into water systems have different sources such as municipal and industrial wastewater, leaching waste disposal systems and agricultural runoff
The purpose of this study is to investigate the capacity for ammonium ion adsorption by agricultural waste/by-products (AWBs), as raw materials without any modifications
The surface properties of pomegranate peel powder (PPP) were investigated by zeta potential measurements, as illustrated in Fig. 2a, b; PPP surface groups are negatively charged in the studied range of pH and solution concentrations
Summary
Nitrogen compounds discharged into water systems have different sources such as municipal and industrial wastewater, leaching waste disposal systems and agricultural runoff. International Journal of Environmental Science and Technology (2021) 18:711–722 which is the predominant nitrogen source and the most common pollutant encountered in water streams and among these methods adsorption is well known as the most simple and cost-effective process (Karri et al 2018). Connected with these environmental challenges, and as a result of the expanding agricultural activities and food production, million tons of agricultural and food waste are disposed worldwide every year. In spite of the growing interest given to the application of these bio-adsorbents, there are many obstacles concerning deep investigation on adsorption mechanisms and comparative studies under defined conditions to prove their efficiency as alternative adsorbents for wastewater treatment (Worch 2012)
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