Preparation of Activated Carbons from Spent Coffee Grounds and Coffee Parchment and Assessment of Their Adsorbent Efficiency

Gustavo A Figueroa Campos,Sorel Tchewonpi Sagu,Pedro Saravia Celis,Inga Block,Andreas Taubert,Harshadrai M Rawel,Jeffrey Paulo H Perez

doi:10.3390/pr9081396

Abstract

The valorization of coffee wastes through modification to activated carbon has been considered as a low-cost adsorbent with prospective to compete with commercial carbons. So far, very few studies have referred to the valorization of coffee parchment into activated carbon. Moreover, low-cost and efficient activation methods need to be more investigated. The aim of this work was to prepare activated carbon from spent coffee grounds and parchment, and to assess their adsorption performance. The co-calcination processing with calcium carbonate was used to prepare the activated carbons, and their adsorption capacity for organic acids, phenolic compounds and proteins was evaluated. Both spent coffee grounds and parchment showed yields after the calcination and washing treatments of around 9.0%. The adsorption of lactic acid was found to be optimal at pH 2. The maximum adsorption capacity of lactic acid with standard commercial granular activated carbon was 73.78 mg/g, while the values of 32.33 and 14.73 mg/g were registered for the parchment and spent coffee grounds activated carbons, respectively. The Langmuir isotherm showed that lactic acid was adsorbed as a monolayer and distributed homogeneously on the surface. Around 50% of total phenols and protein content from coffee wastewater were adsorbed after treatment with the prepared activated carbons, while 44, 43, and up to 84% of hydrophobic compounds were removed using parchment, spent coffee grounds and commercial activated carbon, respectively; the adsorption efficiencies of hydrophilic compounds ranged between 13 and 48%. Finally, these results illustrate the potential valorization of coffee by-products parchment and spent coffee grounds into activated carbon and their use as low-cost adsorbent for the removal of organic compounds from aqueous solutions.

Highlights

20 g of calcium carbonate were added prior the treatments and before calcination, washing and drying steps; final masses after calcination of 16.4 and 17 g of activated carbons were obtained for spent coffee grounds and parchment, respectively
The yield decreased after washing the material with HCl and distilled water to 9.1% for spent coffee grounds and parchment
The results showed that, after treatment, protein content decreased when compared this study, activated carbons were prepared from spent coffee withIncoffee wastewater

Summary

Introduction

Fresh coffee cherries generally undergo several processing steps from harvest to final consumption, including hulling, drying, milling, polishing and roasting. The coffee hulling consists of the removal of the parchment skin from the coffee bean and is generally processed in two main different ways: the dry method, known as the unwashed method, and the wet method, called the washing method. Namely the pulped natural method and the prime washed method, exist, but are less common All these methods involve elimination of the different layers of coffee (coffee pulp, mucilage, and parchment) to produce green coffee beans. Coffee layers are successively removed through a sequence of steps including pulping (coffee pulp), fermentation (mucilage), washing and drying (coffee parchment) [5]

Objectives

Methods

Results

Conclusion