The aim of the study was to screen the waste wood biomass of 10 wood species as biosorbents for synthetic dye Congo Red (CR) removal from water and to single out the most efficient species for further batch biosorption experiments. Euroamerican poplar (EP), the most efficient species achieving 71.8% CR removal and biosorption capacity of 3.3 mg g−1, was characterized by field emission scanning electron microscopy (FE-SEM) and Fourier transform infrared spectroscopy (FTIR). Different factors affecting the biosorption process were investigated: initial biosorbent concentration (1–10 g dm−3), contact time (5–360 min), initial CR concentration (10–100 mg dm−3), and the initial pH (pH = 4–9). The results showed that CR removal efficiency increased with the increase of biosorbent concentration and contact time. Increase of initial CR concentration led to an increase of the biosorption capacity, but also a decrease of CR removal efficiency. The highest CR removal efficiency was achieved at pH = 4, while at pH = 9 a significant decrease was noticed. The percentage of CR removal from synthetic wastewater was 18.6% higher than from model CR solution. The Langmuir model fitted well the biosorption data, with the maximum biosorption capacity of 8 mg g−1. The kinetics data were found to conform to the pseudo-second-order kinetics model.

No abstract

Background and purpose: Wood and wood processing industries are generators of a substantial amount of waste wood biomass, such as wood chips, shavings and sawdust. Such waste is often unused and its disposal can be a serious environmental problem. Different lignocellulosic waste materials have been successfully used as low-cost adsorbents (biosorbents) for the removal of synthetic dyes, as well as other contaminants, from wastewater. The aim of this study was to valorise the waste wood biomass of ten tree species, out of which seven are the most represented species of the Croatian growing stock, as biosorbents for the removal of synthetic dye methylene blue (MB) from model solutions. Materials and Methods: The waste wood biomasses (shavings or sawdust) of ten tree species, namely common beech, pedunculate oak, sessile oak, common hornbeam, narrow-leafed ash, poplar, European silver fir, Norway spruce, European larch and Douglas fir, were dried and milled prior to characterisation and adsorption experiments. Characterisation of the biosorbents was performed by chemical analysis and Fourier transform Fourier transform infrared spectroscopy (FTIR). Upon characterisation, batch adsorption experiments were conducted in order to survey waste wood biomass as potential adsorbents for the removal of synthetic dye MB. The colour removal was monitored spectrophotometrically at predetermined time intervals. Further adsorption experiments were performed using poplar sawdust. The effects of contact time, biosorbent concentration, initial dye concentration, and pH on the adsorption process were investigated. The experimental data obtained by batch adsorption experiments were analysed using adsorption isotherm models (Freundlich and Langmuir). Results: All the tested biosorbents were found to be very effective for the removal of MB from model dye solution, achieving high removal percentages ranging from 93.25 to 98.50%. Poplar sawdust proved to be the most effective. It was shown that MB adsorption process onto poplar sawdust could be interpreted in terms of Langmuir and Freundlich adsorption isotherm models. conclusions: Taken together, these results suggest that waste wood biomass has the potential to be used as a low-cost biosorbent for MB removal from aqueous solutions.

The aim of the study was to prepare a novel adsorbent by chemical modification of hazelnut shells and evaluate its potential for the nitrate removal from model solutions and real wastewater. The characterization of the novel adsorbent, i.e., modified hazelnut shell (MHS) was performed. The adsorbent characterization included the analysis of elemental composition and the surface characteristics analysis by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). The adsorption experiments (batch technique) were performed to investigate the effects of adsorbent concentration, contact time, initial nitrate concentration, and solution pH. The nitrate removal efficiency increased with the increase in MHS concentration and decreased with the initial nitrate concentration. MHS was found to be effective in nitrate removal over a wide pH range (from 2 to 10), and the highest amount of nitrate adsorbed was 25.79 mg g−1 in a model nitrate solution. Depending on the aqueous medium (model solutions or real wastewater samples), it was shown that both Langmuir and Freundlich adsorption isotherm models can be used to interpret the adsorption process. It was found that the kinetics are well described by a pseudo-second order model and the nitrate adsorption process can be controlled by chemisorption. The intraparticle diffusion model has been used to identify an adsorption-controlled process by diffusion mechanisms. Adsorption/desorption experiments in column confirmed that MHS could be successfully used in multiple cycles (at least three), indicating the potential of MHS as an alternative to costly commercial adsorbents for the removal of nitrates from wastewater.

One of the major challenges in sustainable waste management in the agri-food industry following the “zero waste” model is the application of the circular economy strategy, including the development of innovative waste utilization techniques. The conversion of agri-food waste into carriers for the immobilization of enzymes is one such technique. Replacing chemical catalysts with immobilized enzymes (i.e., immobilized/heterogeneous biocatalysts) could help reduce the energy efficiency and environmental sustainability problems of existing chemically catalysed processes. On the other hand, the economics of the process strongly depend on the price of the immobilized enzyme. The conversion of agricultural and food wastes into low-cost enzyme carriers could lead to the development of immobilized enzymes with desirable operating characteristics and subsequently lower the price of immobilized enzymes for use in biocatalytic production. In this context, this review provides insight into the possibilities of reusing food industry wastes, namely, eggshells, coffee grounds, and brown onion skins, as carriers for lipase immobilization.