Novel lanthanum-modified activated carbon derived from pine cone biomass as ecofriendly bio-sorbent for removal of phosphate and nitrate in wastewater

Using predictive models unravel the potential of titanium oxide-loaded activated carbon for the removal of leachate ammoniacal nitrogen

The TiO2 nanocomposite efficiency was determined under optimized conditions with activated carbon to remove ammoniacal nitrogen (NH3-N) from the leachate sample. In this work, the facile impregnation and pyrolysis synthesis method was employed to prepare the nanocomposite, and their formation was confirmed using the FESEM, FTIR, XRD, and Raman studies. In contrast, Raman phonon mode intensity ratio ID/IG increases from 2.094 to 2.311, indicating the increase of electronic conductivity and defects with the loading of TiO2 nanoparticles. The experimental optimal conditions for achieving maximum NH3-N removal of 75.8% were found to be a pH of 7, an adsorbent mass of 1.75 mg/L, and a temperature of 30 °C, with a corresponding time of 160 min. The experimental data were effectively fitted with several isotherms (Freundlich, Hill, Khan, Redlich-Peterson, Toth, and Koble-Corrigan). The notably elevated R2 value of 0.99 and a lower ARE % of 14.61 strongly support the assertion that the pseudo-second-order model compromises a superior depiction of the NH3-N reduction process. Furthermore, an effective central composite design (CCD) of response surface methodology (RSM) was employed, and the lower RMSE value, precisely 0.45, demonstrated minimal disparity between the experimentally determined NH3-N removal percentages and those predicted by the model. The subsequent utilization of the desirability function allowed us to attain actual variable experimental conditions.

Phosphate recovery from aqueous phase using novel zirconium-based adsorbent

This study aims to document the phosphate ion (PO43-) adsorption capacity of a novel zirconium-based adsorbent. The physicochemical properties of the adsorbent are investigated using an array of methods and metrics such as electron microscopy, X-ray diffraction, thermal analysis, specific surface area, pore volume, pH point of zero charge (pHpzc), and surface hydroxyl groups. The batch method is used to elucidate PO43- adsorption capacity. Results suggested that the adsorption of PO43- was based on an internal diffusion and a monolayer adsorption. We also clarified that the pH of the solution significantly impacted the adsorption. Moreover, the adsorbent shows the ability to not only adsorb but also desorb PO43- for at least five cycles, based on an adsorption mechanism that we document. These findings indicate that this adsorbent could serve as a major industrial PO43- adsorbent.

Preparation of Lanthanum-Modified Tea Waste Biochar and Its Adsorption Performance on Fluoride in Water

In this study, tea waste was used as a raw material, and TBC (tea waste biochar) was prepared by pyrolysis at 700 °C. La(NO3)3·6H2O was used as the modifier to optimize one-way modification; the orthogonal experiment was undertaken to determine the optimal preparation conditions; and La-TBC (lanthanum-modified biochar) was obtained. The key factors for the adsorption of fluoride by La-TBC were investigated by means of batch adsorption experiments, and kinetics and isothermal adsorption experiments were carried out on the adsorption of fluoride in geothermal hot spring water. The adsorption mechanism of fluoride by La-TBC was analyzed via characterization methods such as SEM-EDS (Scanning Electron Microscope and Energy Dispersive Spectrometer), BET (Brunauer-Emmett-Teller), FTIR (Fourier transform infrared), XRD (X-ray diffraction), and so on. The results show that La-TBC had the best adsorption effect on fluoride at pH 7. The process of adsorption of fluoride follows the pseudo-second-order kinetics and Langmuir isothermal model, and the maximum theoretical adsorption quantity was 47.47 mg/g at 80 °C, while the removal rate of fluoride from the actual geothermal hot spring water reached more than 95%. The adsorption process was dominated by the monolayer adsorption of chemicals, and the mechanisms mainly include pore filling, ion exchange, and electrostatic interaction.

Common Buckthorn Engineered Biochar (Rhamnus Cathartica), Calcined Quagga Mussel Shells (Dreissena Rostriformis), Pickled Steel, and Steel Slag as Filter Media for the Sorption of Phosphorus from Agricultural Runoff

The reuse of waste residuals as reactive media is a sustainable solution to remove phosphorus (P) from wastewater and reduce eutrophication. Large reactive waste media filters incorporated in edge-of-field treatment systems could reduce P loading from agricultural fields. We measured the treatment potential of regionally available waste residuals (i.e., calcined quagga mussel shells (CSHELL), magnesium activated biochar (MGBC), pickled steel (PSTEEL), and steel slag (SLAG)) for dissolved P removal. CSHELL and MGBC had elevated sorption capacities (64,419 and 50,642 mg kg−1, respectively) in comparison to SLAG and PSTEEL (14,541 mg kg−1 and 736 mg kg−1, respectively). However, CSHELL requires long reaction times for removal (22% removal after 1.5 h) and P sorbed to MGBC is removed with DI, reducing treatment potential. SLAG and PSTEEL were the only media with significant reductions of agricultural runoff and had the greatest overall treatment potential. SLAG is recommended for removal and replacement systems while PSTEEL is suitable for larger systems designed for regeneration on site.

Recycling phosphorus and calcium from aquaculture waste as a precursor for hydroxyapatite (HAp) production: a review

Water contaminated with phosphorus needs to be managed efficiently to ensure that clean water sources will be preserved. Aquaculture plays an essential role in supplying food and generating high revenue. However, the quantity of phosphorus released from aquaculture effluents is among the major concerns for the environment. Phosphorus is a non-renewable, spatially concentrated material essential for global food production. Phosphorus is also known as a primary source of eutrophication. Hence, phosphorus recovery and separation from different wastewater streams are mandatory. This paper reviews the source of phosphorus in the environment, focusing on aquaculture wastewater as a precursor for hydroxyapatite formation evaluates the research progress on maximizing phosphorus removal from aquaculture wastewater effluents and converting it into a conversion. Shrimp shell waste appears to be an essential resource for manufacturing high-value chemicals, given current trends in wealth creation from waste. Shrimp shell waste is the richest source of calcium carbonate and has been used to produce hydroxyapatite after proper treatment is reviewed. There have been significant attempts to create safe and long-term solutions for the disposal of shrimp shell debris. Through the discussion, the optimum condition of the method, the source of phosphorus, and the calcium are the factors that influence the formation of hydroxyapatite as a pioneer in zero-waste management for sustainability and profitable approach. This review will provide comprehensive documentation on resource utilization and product development from aquaculture wastewater and waste to achieve a zero-waste approach.

Carbonaceous materials for removal and recovery of phosphate species: Limitations, successes and future improvement

The carbonaceous materials have gained significant interest for the phosphorus species remediation and recovery in the last decade. Carbonaceous materials present many unique features, such as cost effective, availability, environmentally friendly, and high removal efficiency that make them a promising adsorbent. In this review, the recent application of carbonaceous materials including activated carbon (AC), graphene and graphene oxide (GO), lignin, carbon nanotubes (CNTs), and gC₃N₄ for phosphate removal and recovery were comprehensively summarized. The kinetics and isotherm models, removal mechanisms, and effects of operating parameters are reported. The reusability, lifetime of carbonaceous materials, and impact of modification were also considered. The modified carbonaceous materials have significantly high phosphate adsorption capacity compared to unmodified adsorbents. Namely, MgO-functionalized lignin-based bio-charcoal exhibited a 906.8 mg g^-1 of capacity as the highest one among other reviewed materials. The modification of carbonaceous materials with various elements has been presented to improve the surface functional groups, surface area and charge, and pore volume and size. Among these loaded elements, iron has been effectively used to provide a prospect for magnetic recovery of the adsorbent as well as increase phosphate adsorption. Furthermore, the phosphate recovery methods, phosphate removal efficiency of carbonaceous materials, the limitations, important gaps in the literature, and future studies to enhance applicability of carbonaceous materials in real scale are also discussed.

Removal and recovery of phosphate using a novel calcium silicate hydrate composite starch cryogel

Phosphate is a major pollutant that deteriorates water quality and causes eutrophication, a novel calcium silicate hydrate composite cryogel (Cry-CSH) was thus successfully prepared for phosphate removal and recovery in this work. Calcium silicate hydrate (C-S-H) was mixed with the gel precursor (7.5% w/w) prepared from native starch and limewater (saturated calcium hydroxide solution as the cross-linker). The mixture was frozen and thawed for 3 cycles giving an interconnected macroporous composite. This had C-S-H nanoparticles (75 mg) immobilized on a monolithic floatable cryogel network (2.5 cm diameter × 1.0 cm height) enabling an easier recovery and without the losses that occur when using C-S-H nanoparticles. The phosphate adsorption reaches equilibrium at 120 min with adsorption capacity of 2.50 mgPO₄^3-/g_Cry-CSH (65.42 mgPO₄^3-/g_C-S-H) under optimum conditions. Adsorption equilibrium data were well fit by the Freundlich isotherm model, while kinetic results were well fit by the pseudo second-order model. The calculated activation energy (E_a) of 43.9 kJ/mol indicates chemical adsorption, while a positive change in enthalpy (ΔH⁰, 19.3 kJ/mol) indicates the endothermic nature of phosphate adsorption. Cry-CSH can remove phosphate from wastewater and effluent samples with excellent removal efficiency (>98%). It can float on water surface for at least 105 days without damage, while its phosphate adsorbed form can be biodegraded within 10 days under soil buried conditions. Thus, this work demonstrated the significant potential of Cry-CSH for practical and environmentally friendly phosphate removal and recovery.

Enhanced recovery of phosphate as a value-added product from wastewater by using lanthanum modified carbon-fiber

The aim of this study is to present the potential of activated carbon fiber (CF) impregnated with lanthanum (La) as a novel adsorbent (La-CF) of phosphate-phosphorus (P) and to assess the value-added due to P-recovery from wastewater using La-CF. The CF were loaded with La and the loaded CF was then calcined at 500 °C. The La-CF adsorbent was used in a series of batch experiments to characterize the adsorption of P at pH of 6-10 and P concentrations of 1-200 mg/L. Physical-chemical properties such as surface morphology, surface charge, surface area, and surface chemistry were determined for the La-CF. The La-CF exhibited adsorption capacity of 196.5 mg/g, fast sorption kinetics and high selectivity for P removal from aqueous solution. La-CF removed 97.3% of P from wastewater and achieved P-level to below 2 mg/L. It was repetitively reused over 10 times in successive cycles to remove P from wastewater. The value-added by recovery of P from wastewater was calculated at around 0.12 US$/L, demonstrating economic benefits of La-CF. In conclusion, the successful removal, recycling, and recovery value-added of P using La-CF adsorbent displayed good potential for developing the technology for treatment of wastewaters to recover valuable compounds such as phosphorus.

Natural core-shell structure activated carbon beads derived from Litsea glutinosa seeds for removal of methylene blue: Facile preparation, characterization, and adsorption properties

In this study, natural core-shell structure activated carbon beads (ACBs) from Litsea glutinosa seeds were successfully produced, characterized, and applied for adsorption of methylene blue (MB). The ACBs were prepared using single-step carbonization-activation with NaHCO₃ at the optimized activation temperature, time, and activating agent concentration of 450 °C, 60 min, and 5%, respectively. Batch experiments were performed to determine the optimum adsorption conditions, suitable kinetic and isotherm models, and thermodynamic parameters for the adsorption of MB onto ACBs. The results showed that the ACBs were displayed as highly porous natural core-shell spheres with a diameter of about 5 mm. The adsorption of MB dye on ACBs was a spontaneous endothermic process, followed the Langmuir isotherm and the pseudo-second-order kinetic models with the rate-controlling step of both external diffusion and intra-particle diffusion. At the optimum conditions (pH of 9, the contact time of 10 h, the temperature of 40 °C, and an adsorbent dosage of 6 g/L), the maximum adsorption capacity reached 29.03 mg/g. The thermal method turned out to be more suitable for regenerating ACBs compared to the chemical method. The ACBs exhibited high reusability and stability, its adsorption efficiency could maintain more than 90% after five consecutive cycles of use. The electrostatic attraction, π-π interaction, hydrogen bonding, and pore-filling were identified as primary contributions to the adsorption mechanism. The overall results revealed that the ACBs could be used as a potential adsorbent for removing MB from water media.

Review of phosphate removal from water by carbonaceous sorbents

In the last decades, phosphate is considered the main cause of eutrophication and has received substantial attention from the scientific community. Phosphate is a major pollutant that deteriorates water quality, which has been increasing in water resources, primarily due to the increasing global population and corresponding activities. Adsorption technology is amongst the different technologies used to decrease the phosphate levels in water, and has been found to be highly effective even at low phosphate concentrations. Carbonaceous materials and their composites have been widely used for phosphate removal due to their exceptional surface properties and high phosphate sorption capacity. Considering the importance of the topic, this study reviews the reported literature in the field of adsorptive removal of phosphate over various carbon-based adsorbents such as activated carbon, charcoal, graphene, graphene oxide, graphite and carbon nanotubes. Moreover, insights into the adsorption behaviour, experimental parameters, mechanisms, thermodynamics, effect of coexisting ions and the possible desorption processes of phosphate onto modified and unmodified carbonaceous adsorbents are also considered. Finally, research challenges and gaps have been highlighted.

Assessment of the Composition of Forest Waste in Terms of Its Further Use

This paper presents the results of the analysis of the chemical composition and content of heavy metal contamination in forest logging residues, in order to assess the possibility for their further utilisation. The samples were divided into 9 groups, which included coniferous tree cones, wood, and other multi-species logging residues. The elementary composition, ash content, and calorific value were determined as energy use indicators for the samples. Additionally, the content of heavy and alkali metals, which may affect combustion processes and pollutant emissions, was tested. The high content of heavy metals may also disqualify these residues for other uses. The research shows that the test residues are suitable for energy use due to their high calorific value and low content of heavy metals. However, an increased ash content in some samples and the presence of alkali metals, causing high-temperature corrosion of boilers, may disqualify them as a potential fuel in the combustion process. The forest residues may be used in other thermal processes such as pyrolysis or gasification. A low content of heavy metals and a high content of organic matter permit the use of these residues for the production of adsorbents or composite materials.

New frontiers from removal to recycling of nitrogen and phosphorus from wastewater in the Circular Economy

Nutrient recovery technologies are rapidly expanding due to the need for the appropriate recycling of key elements from waste resources in order to move towards a truly sustainable modern society based on the Circular Economy. Nutrient recycling is a promising strategy for reducing the depletion of non-renewable resources and the environmental impact linked to their extraction and manufacture. However, nutrient recovery technologies are not yet fully mature, as further research is needed to optimize process efficiency and enhance their commercial applicability. This paper reviews state-of-the-art of nutrient recovery, focusing on frontier technological advances and economic and environmental innovation perspectives. The potentials and limitations of different technologies are discussed, covering systems based on membranes, photosynthesis, crystallization and other physical and biological nutrient recovery systems (e.g. incineration, composting, stripping and absorption and enhanced biological phosphorus recovery).