Pistachio (Pistacia vera) waste as adsorbent for wastewater treatment: a review

The by-product from pistachio (Pistachia vera) has been valorised over the years as an adsorbent material for water treatment. The aim of this review was to synthesise the empirical findings on the uptake of different pollutants using adsorbents developed from pistachio waste. This was done to evaluate the progress of research on the subject matter, identify knowledge gaps and propose interesting areas for future work. Iran was observed to be a major source country (31%) of pistachio feedstock for adsorbent preparation. The highest reported specific surface area for pistachio adsorbent was 1884 m(2)/g for a carbon activated by NH4NO3 + NaOH and carbonised at 800 degrees C. Pistachio adsorbents showed very good removal efficiencies (> 90% in most cases) for both dyes, heavy metals, pharmaceuticals and other compounds. Isotherm and kinetics modelling was always best-fit to the classical Langmuir and Freundlich models and the pseudo-second-order kinetics model, respectively. HCl was the regularly used eluent for heavy metals desorption, while alkalis and organic acids were more regularly used for dyes. Interesting areas for future work include adsorbent preparation by physical activation, research interest in emerging contaminants, improvement of adsorbent desorption, utilisation of statistical physics modelling tools and the investigation of spent adsorbent disposal.

Automated summary

Adsorbent materials developed from pistachio waste have shown high removal efficiencies for various pollutants, with Iran being a major source country. Studies have found that the adsorption behavior of pistachio adsorbents often align well with the Langmuir and Freundlich models, as well as the pseudo-second-order kinetics model.