Study of the Digestate as an Innovative and Low-Cost Adsorbent for the Removal of Dyes in Wastewater

Abstract

Digestate, as an urban solid waste, was considered as an innovative adsorbent for colorant polluted wastewater. Batch adsorption experiments were carried out using digestate as an adsorbent material to remove various dyes belonging to different categories. The removal rate and adsorption capacity of dyes were evaluated and the dose of digestate, contact time, and initial dye concentration were studied. The maximum removal rate was approximately 96% for Methylene Blue. The equilibrium time for the Methylene Blue was 4 h, while for other dyes, a longer contact time was required to reach the equilibrium. The suspicion of colloidal matter release into the solution from solid fraction of the digestate led to the investigation of the consequence of a washing step of the digestate adsorbent upstream the adsorption experiment. Washed and not washed adsorbents were tested and the differences between them in terms of dye removal were compared. Moreover, experimental data were fitted by pseudo-first order, pseudo-second order, and intra-partial diffusion kinetic models as well as Langmuir, Freundlich, and Sips isotherm models. The results from fitted models showed that the adsorption of various dyes onto the digestate was mostly well fitted by the Langmuir isotherm and pseudo-second-order kinetic model.

Recent Advances on Innovative Materials from Biowaste Recycling for the Removal of Environmental Estrogens from Water and Soil

“…DG has also been directed to bio-oxidative conversion processes such as composting and vermicomposting [ 60 ], used in the preparation of biofilters and biobeds in mixtures with other C-rich substrates [ 61 ] or converted thermically to produce BC [ 41 ]. However, recent studies have shown that some DG properties, such as the presence of surface reactive functional groups, porosity and a fairly large surface area, can make this material a good candidate for the removal of inorganic and organic contaminants by adsorption [ 12 , 62 ].…”

“…The first work (on Scopus database) on the use of DG for decontamination purposes was carried out by Mukherjee et al [ 61 ], who used soil/DG biomixtures to obtain biobeds and biofilters to immobilize pesticides with contrasting physicochemical properties. Yao et al [ 62 ] used an unmodified DG from OFMW for the removal of dyes from textile wastewater and reported the satisfactory performance of this material, thus demonstrating that DG could be a promising renewable and cost-effective decontaminant. A very recent study on adsorption/desorption of EEs on/from DG demonstrated that this material has a remarkable efficiency in removing BPA and, especially, OP from water and that the occurrence of a positive hysteresis guarantees a long-lasting retention of the pollutants [ 12 ].…”

Use of the Solid By-Product of Anaerobic Digestion of Biomass to Remove Anthropogenic Organic Pollutants with Endocrine Disruptive Activity

“…Recently, Yao et al [35], investigating the capacity of a DIG to remove various dyes from a wastewater, reported an increase in the adsorption capacity as the solution/DIG ratio increased. The authors commented that this could be due to the large number of sites not occupied by the dye when the DIG was at a high dosage, thus reducing the adsorption capacity of the latter [35]. Considering the physicochemical properties of the four molecules, as expected, the affinity for the DIG (MET < BPA < BOS < OP) was inversely related to their solubility in water.…”

“…At the highest ratio (500), the percentages of MET, BPA, BOS and OP adsorbed on the DIG after 24-h interaction were approximately 11, 45, 24 and 66% of the initial compound added (40 µg), respectively. Recently, Yao et al [35], investigating the capacity of a DIG to remove various dyes from a wastewater, reported an increase in the adsorption capacity as the solution/DIG ratio increased. The authors commented that this could be due to the large number of sites not occupied by the dye when the DIG was at a high dosage, thus reducing the adsorption capacity of the latter [35].…”

Using N-Ovel Coated Sand as Reactive Bed in Permeable Barrier for Elimination of Methyl Orange Dye From Groundwater*

“…It forms type of azo dyes that have high resistance to biodegradability. Thus, this dye is utilized as a model for investigation the cleanup of environment (31). The continuous up-to-date for methods of remediation must be conducted to control of this contamination.…”