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Equilibrium Processes in Nutrient Removal Technologies from Wastewater, Waste Reuse in Construction Materials

A special issue of Water (ISSN 2073-4441). This special issue belongs to the section "Wastewater Treatment and Reuse".

Deadline for manuscript submissions: closed (1 December 2021) | Viewed by 12137

Special Issue Editor

Dr. Ivar Zekker

E-Mail Website
Guest Editor
Institute of Chemistry, University of Tartu, 50090 Tartu, Estonia
Interests: pyrolysis-related adsorbents; biomass-based adsorbents; chemically modified adsorbents; wastewater field study
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Phosphorus and nitrogen in the effluent of wastewater treatment plants (WWTPs) lead to eutrophication and the deterioration of the receiving water environments. Municipal wastewater discharge, which increases with the urbanization process, has become a serious threat to aquatic ecosystems in urban areas. However, existing wastewater treatment remains at a low level. Therefore, it has become a trend to upgrade municipal WWTPs and to implement more stringent discharge standards for water environmental regulation. The carbon-to-nitrogen ratio (C/N) is generally low in wastewater treatments plants using biogas, which leads to insufficient carbon sources for nutrient removal in WWTPs. An anaerobic ammonium oxidation process can be applied to nutrient-rich wastewater after biogas plant applications as well as after organic carbon has been used in microbial fuel cells for generating energy or enhancing nitrogen and phosphorus removal. Equilibrium processes would define the amounts of ions present in different waste streams. Denitrifying phosphorus removal enables energy savings from the aerobic stage using nitrate as an electron acceptor to capture phosphorus.

Dr. Ivar Zekker
Guest Editor

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Keywords

  • Anammox
  • Equilibrium processes
  • Phosphorus removal
  • Nutrient removal
  • Biotechnology
  • Wastewater treatment
  • Construction Materials

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Published Papers (3 papers)

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Research

19 pages, 6371 KiB  
Article
Preparation of Pd–Ni Nanoparticles Supported on Activated Carbon for Efficient Removal of Basic Blue 3 from Water
by Sultan Alam, Muhammad Sufaid Khan, Ali Umar, Rozina Khattak, Najeeb ur Rahman, Ivar Zekker, Juris Burlakovs, Sergio S. dC Rubin, Makarand Madhao Ghangrekar, Gourav Dhar Bhowmick, Anna Kallistova, Nikolai Pimenov, Abbas Khan and Muhammad Zahoor
Water 2021, 13(9), 1211; https://doi.org/10.3390/w13091211 - 27 Apr 2021
Cited by 41 | Viewed by 4508
Abstract
Pd–Ni nanoparticles supported on activated carbon (Pd–Ni/AC) were prepared using a phase transfer method. The purpose of synthesizing ternary composites was to enhance the surface area of synthesized Pd–Ni nanoparticles, as they have a low surface area. The resulting composite was characterized by [...] Read more.
Pd–Ni nanoparticles supported on activated carbon (Pd–Ni/AC) were prepared using a phase transfer method. The purpose of synthesizing ternary composites was to enhance the surface area of synthesized Pd–Ni nanoparticles, as they have a low surface area. The resulting composite was characterized by scanning electronic microscopy (SEM), X-ray diffraction (XRD) and energy-dispersive X-ray spectroscopy (EDX) for investigating its surface morphology, particle size, percentage of crystallinity and elemental composition, respectively. The XRD data and EDX analysis revealed the presence of Pd–Ni alloys impregnated on the AC. Pd–Ni/AC was used as an adsorbent for the removal of the azo dye basic blue 3 from an aqueous medium. Kinetic and isotherm models were used to calculate the adsorption parameters. The most suitable kinetic model amongst the applied models was the pseudo-second-order model, confirming the chemisorption characteristics of the process, and the most suitable isotherm model was the Langmuir model, with a maximum adsorption capacity of 333 mg/g at 333 K. Different experimental parameters, such as the adsorbent dosage, pH, temperature and contact time, were optimized. The optimum parameters reached were: a pH of 12, temperature of 333 K, adsorbent dosage of 0.01 g and optimum contact time of 30 min. Moreover, the thermodynamics parameters of adsorption, such as Gibbs free energy (ΔG°), enthalpy (ΔH°) and entropy (ΔS°), showed the adsorption processes being exothermic with values of ΔH° equal to −6.206 kJ/mol and being spontaneous with ΔG° values of −13.297, −13.780 and −14.264 kJ/mol, respectively at 293, 313 and 333 K. An increase in entropy change (ΔS°) with a value of 0.0242 kJ/mol K, indicated the enhanced disorder at a solid–solution interface during the adsorption process. Recycling the adsorbent for six cycles with sodium hydroxide and ethanol showed a decline in the efficiency of the selected azo dye basic blue 3 up to 79%. The prepared ternary composite was found effective in the removal of the selected dye. The removal of other pollutants represents one of the possible future uses of the prepared adsorbent, but further experiments are required. Full article
(This article belongs to the Special Issue Equilibrium Processes in Nutrient Removal Technologies from Wastewater, Waste Reuse in Construction Materials)
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17 pages, 23801 KiB  
Article
Synthesis and Characterization of Pd-Ni Bimetallic Nanoparticles as Efficient Adsorbent for the Removal of Acid Orange 8 Present in Wastewater
by Ali Umar, Muhammad Sufaid Khan, Sultan Alam, Ivar Zekker, Juris Burlakovs, Steven S. dC Rubin, Gourav Dhar Bhowmick, Anna Kallistova, Nikolai Pimenov and Muhammad Zahoor
Water 2021, 13(8), 1095; https://doi.org/10.3390/w13081095 - 15 Apr 2021
Cited by 48 | Viewed by 4193
Abstract
In this study palladium-nickel (Pd-Ni) nanoparticles supported on carbon and cerium oxide (Pd-Ni/AC-CeO2) were synthesized by a transfer phase method and characterized by scanning electronic microscopy (SEM), X-ray diffraction (XRD), and energy-dispersive X-ray spectroscopy (EDX). The XRD and SEM data concluded [...] Read more.
In this study palladium-nickel (Pd-Ni) nanoparticles supported on carbon and cerium oxide (Pd-Ni/AC-CeO2) were synthesized by a transfer phase method and characterized by scanning electronic microscopy (SEM), X-ray diffraction (XRD), and energy-dispersive X-ray spectroscopy (EDX). The XRD and SEM data concluded the presence of alloy formation between Pd and Ni. The synthesized particles were used as an adsorbent for removal of azo dye acid orange-8 (AO-8) from water and were found to be effective in removal (over 90% removal efficiency) of the selected dye. Different kinetics and equilibrium models were applied to calculate the adsorption parameters. The most suitable model that best fitted the equilibrium data was the Langmuir model and maximum adsorption capacities were 666.6, 714 and 769 mg/g at 293, 313 and 333 K, respectively, with R2 values closed to 1 while in the case of the kinetics data the best fit was obtained with a pseudo-second order kinetics model with a high R2 value. Furthermore, the adsorption thermodynamics parameters such as free energy, enthalpy, and entropy were calculated and the adsorption process was to found be exothermic with a value of ΔH° (−7.593 kJ mol−1), spontaneous as ΔG° values were negative (−18.7327, −19.4870, and −20.584 kJ/mol at 293, 313 and 333 K, respectively). A positive entropy change ΔS° with a value of 0.0384 kJ /mol K indicates increased disorder at the solid–solution interface during the adsorption process. An attempt was made to recycle the Pd-Ni/AC-CeO2 with suitable solvents and the recycled adsorbent was reused for 6 cycles with AO-8 removal efficiency up to 80%. Based on findings of the study, the synthesized adsorbent could effectively be used for the removal of other pollutants from wastewater, however, further studies are needed to prove the mechanisms. Full article
(This article belongs to the Special Issue Equilibrium Processes in Nutrient Removal Technologies from Wastewater, Waste Reuse in Construction Materials)
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9 pages, 652 KiB  
Article
Relationship between Phase Composition and Mechanical Properties of Peat Soils Stabilized Using Oil Shale Ash and Pozzolanic Additive
by Ergo Rikmann, Ivar Zekker, Tõnis Teppand, Vello Pallav, Merrit Shanskiy, Uno Mäeorg, Toomas Tenno, Juris Burlakovs and Jüri Liiv
Water 2021, 13(7), 942; https://doi.org/10.3390/w13070942 - 30 Mar 2021
Cited by 10 | Viewed by 2562
Abstract
Construction of road embankments in peatlands commonly involves replacement of the peat with a fill-up soil of an adequate load-bearing capacity. This usually requires a lowering of the water level, turning a peatland from a carbon sink to a source of greenhouse gases. [...] Read more.
Construction of road embankments in peatlands commonly involves replacement of the peat with a fill-up soil of an adequate load-bearing capacity. This usually requires a lowering of the water level, turning a peatland from a carbon sink to a source of greenhouse gases. Thus, alternatives are sought that are less costly in both economic and ecological terms. Mass-stabilization technology can provide a cheap substitute for Portland cement. Calcareous ashes (waste materials), supplemented with pozzolanic and alkali additives to facilitate and accelerate the setting and hardening processes, are attractive alternatives to soil excavation or replacement techniques. Silica fume and waterglass were used as pozzolanic agents and KOH as a soil-alkalizing agent. X-ray fluorescence (XRF), Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) analyses and stress–strain tests were performed for the hardened samples. Crystallization of alkali feldspars was observed in all test samples. Comparable hardening of peat soil was achieved for both ashes. It was shown that the ashes of Estonian kukersite (oil shale) from both pulverized firing and a circulating fluidized bed incineration process (produced in energy sector as quantitatively major solid waste in Estonia) can be used as binding agents for peat stabilization, even without the addition of Portland cement. Hardened peat soil samples behaved as a ductile material, and the cellulose fibers naturally present in peat gave the peat–ash composite plasticity, acting mechanically in the same way as the steel or glass fiber in ordinary reinforced concrete. The effect of peat fiber reinforcement was higher in cases of higher load and displacement of the composite, making the material usable in ecological constructions. Full article
(This article belongs to the Special Issue Equilibrium Processes in Nutrient Removal Technologies from Wastewater, Waste Reuse in Construction Materials)
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