Wastewater treatment is a topic of primary interest with regard to the environment. Diclofenac is a common analgesic drug often detected in wastewater and surface water. In this paper, three commonly available agrifood waste types (artichoke agrowaste, olive-mill residues, and citrus waste) were reused as sorbents of diclofenac present in aqueous effluents. Citrus-waste biomass for a dose of 2 g·L⁻¹ allowed for removing 99.7% of diclofenac present in the initial sample, with a sorption capacity of 9 mg of adsorbed diclofenac for each gram of used biomass. The respective values obtained for olive-mill residues and artichoke agrowaste were around 4.15 mg·g⁻¹. Advanced oxidation processes with UV/H₂O₂ and UV/HOCl were shown to be effective treatments for the elimination of diclofenac. A significant reduction in chemical oxygen demand (COD; 40–48%) was also achieved with these oxidation treatments. Despite the lesser effectiveness of the sorption process, it should be considered that the reuse and valorization of these lignocellulosic agrifood residues would facilitate the fostering of a circular economy.

Nitrate (NO₃⁻) pollution of surface and groundwater bodies is a global problem of increasing concern, which has stimulated significant research interest. Nitrogen is crucial for life as a macronutrient for living organisms on Earth, but the global nitrogen cycle has been seriously altered by intensification of human activities, leading to eutrophication and hypoxic conditions of aquatic ecosystems. Due to nitrogen overfertilization, intensive agricultural practices generate huge nitrate fluxes that inadvertently deteriorate water quality. Different industrial processes also contribute to NO₃⁻ pollution in the environment. There are multiple technologies capable of achieving effective denitrification of waterbodies to ensure safe NO₃⁻ levels. Either separation-based or transformation-based denitrification technologies must address the challenges of by-product generation, increased energy demand, and reduced environmental footprint. This paper highlights the most used approaches, along with some promising alternatives for remediation of nitrate-polluted waters.

The sustainable management of biomass is a key global challenge that demands compliance with fundamental requirements of social and environmental responsibility and economic effectiveness. Strategies for the valorization of waste biomass from agrifood industries must be in line with sustainable technological management and eco-industrial approaches. The efficient bioremoval of the pesticides imazalil and thiabendazole from aqueous effluents using waste biomass from typically Mediterranean agrifood industries (citrus waste, artichoke agrowaste and olive mill residue) revealed that these residues may be transformed into cost-effective biosorbents. Agrifood wastes present irregular surfaces, many different sized pores and active functional groups on their surface, and they are abundant in nature. The surface and adsorptive properties of olive mill residue, artichoke agrowaste and citrus waste were characterized with respect to elemental composition, microstructure, crystallinity, pore size, presence of active functional groups, thermal stability, and point of zero charge. Olive mill residue showed the highest values of surface area (Brunauer–Emmett–Teller method), porosity, crystallinity index, and pH of zero point of charge. Olive mill residue showed the highest efficiency with sorption capacities of 9 mg·g⁻¹ for imazalil and 8.6 mg·g⁻¹ for thiabendazole.

Adsorption process is widely used for the removal of wastewater contaminants. Classic adsorption units are fixed beds and membrane filtration systems. In this work a novel configuration of a bench scale spinning adsorber submerged filter is proposed. Different prototypes of cylindric, truncated cone or prismatic spinning adsorbers were studied using activated carbon of different particle sizes GAC (1.5 mm, Granulated), μGAC (0.475 mm, microGranulated), and cPAC (0.237 mm, coarse Powder) as adsorbent, and azorubine as model adsorbate. High maximum azorubine adsorptions per unit mass of adsorbent of 214, 225 and 275 mg/g for GAC, μGAC and cPAC, respectively, were obtained using the Langmuir isotherm adsorption model. Batch adsorption followed pseudo-second order kinetics, and adsorbate uptake rate increased with decreasing adsorbent particle size. Best adsorption unit was a tank equipped with a spinning rectangular prism adsorber prototype all made of stainless-steel woven wire filter of 180 mesh size. Running at 600 rpm and filled with a high cPAC concentration (25 g/L), adsorber can remove azorubine at similar rates that the use of free moving cPAC. Adsorber unit can run in continuous mode and works even better as a novel spinning submerged filter where filtered flow exits from a central pipe axis. This integrated adsorption-submerged filtration operation mode offer the possibility of adding a high initial dose or a continuous dosing of adsorbent in the tank, increasing the adsorbent concentration of the unit. This system can also offer novel opportunities for wastewater contaminants removal using different adsorbent materials located separately.

The removal of antibiotics from wastewater is receiving considerable attention to fulfill water quality parameters required for reuse. This study compares a spinning submerged filter adsorber with a fixed bed adsorber for continuous antibiotic removal. Adsorbers were evaluated with micro granular activated carbon (μGAC: 508 μm), coarse powder activated carbon (cPAC: 197 μm), powder activated carbon (PAC: 77 μm), and a domestic wastewater effluent spiked with a mixture of amoxicillin, sulfamethoxazole, and levofloxacin with concentrations ranging from 10 to 50 mg/L. The fixed bed adsorber packed with cPAC was the most efficient adsorber running with wastewater spiked with 50 mg/L of each antibiotic and an empty bed contact time (EBCT) of 4.5 min. The spinning submerged filter adsorber configuration also provided high removal effectiveness using a 15 g/L concentration of PAC but with a lower hydraulic retention time (HRT) of 40 min. This adsorption unit can be filled with small PAC particles, unlike packed beds, and PAC concentrations can be increased up to 150 g/L if necessary. It combines adsorption and filtration with a completely mixed mode of operation in which the PAC concentration can be adapted to effluent micropollutant concentrations, making it an interesting alternative for adsorption processes.

Olive mill residues have been valorized by chemical modification with amines to improve their adsorption capacity and to be used as a low-cost bioadsorbent for nitrate removal. The Taguchi method was used to optimize the process. By performing a three-factor analysis with three levels, it was possible to significantly reduce the number of experiments to be performed and to obtain the best working conditions. The results of the Taguchi method showed that the highest adsorption capacity was 110 mg·g⁻¹ with a functionalized biomass dose of 1 g·L⁻¹ using an initial nitrate concentration of 500 mg·L⁻¹. Field emission scanning electron microscopy (FESEM) and Fourier transform infrared spectroscopy (FTIR) were used to characterize the surface morphology and study the chemical changes that occurred in the biomass. For the best conditions of the Taguchi approach, the kinetic and equilibrium aspects of the adsorption process were analyzed. The adsorption isotherms obtained were successfully fitted to the Freundlich (R² = 0.98) and Langmuir (R² = 0.97) models. The kinetics of the process were studied, and the data obtained fit very well to the pseudo-second-order model (R² = 0.99). The adsorption values obtained suggest that it is a bioadsorbent with great potential for nitrate retention in aqueous solutions.