Ultrasonic power combined with seed materials for recovery of phosphorus from swine wastewater via struvite crystallization process

Resource recovery of high value-added products from wastewater: Current status and prospects

Wastewater resource recovery not only allows the extraction of value-added products and offsets the operational costs of wastewater treatment, but it is also conducive to alleviating adverse environmental issues due to energy and chemical inputs and associated emissions. A number of attractive compounds such as alginate-like polymers, struvite, polyhydroxyalkanoates, and sulfated polysaccharides, were found and successfully obtained from wastewater and have a wide range of application prospects. The aim of this work is to provide a comprehensive review of recent advances in recovery of these popular products from wastewater, and their physicochemical properties, main sources, and current recovery status are summarized. Various factors influencing the recovery performance of these materials are thoroughly discussed. Moreover, the research needs and future directions towards wastewater resource recovery are highlighted. This study can provide valuable insights for future research endeavors aiming to improve wastewater resource recovery through the retrieval of high value-added products.

Efficient removal of phosphorus and nitrogen from aquatic environment using sepiolite-MgO nanocomposites: preparation, characterization, removal performance, and mechanism

Excessive phosphorus will lead to eutrophication in aquatic environment; the efficient removal of phosphorus is crucial for wastewater engineering and surface water management. This study aimed to fabricate a nanorod-like sepiolite-supported MgO (S-MgO) nanocomposite with high specific surface area for efficient phosphate removal using a facile microwave-assisted method and calcining processes. The impact of solution pH, adsorbent dosage, contact time, initial phosphate concentrations, Ca2+ addition, and N/P ratio on the phosphate removal was extensively examined by the batch experiments. The findings demonstrated that the S-MgO nanocomposite exhibited effective removal performance for low-level phosphate (0 ~ 2.0 mM) within the pH range of 3.0 ~ 10.0. Additionally, the nanocomposite can synchronously remove phosphate and ammonium in high-level nutrient conditions (> 2.0 mM), with the maximum removal capacities of 188.49 mg P/g and 89.78 mg N/g. Quantitative and qualitative analyses confirmed the successful harvesting of struvite in effluent with high-phosphate concentrations, with the mechanisms involved attributed to a synergistic combination of sorption and struvite crystallization. Due to its proficient phosphate removal efficiency, cost-effectiveness, and substantial removal capacity, the developed S-MgO nanocomposite exhibits promising potential for application in phosphorus removal from aquatic environments.

The competitive and selective adsorption of heavy metals by struvite in the Pb(II)-Cd(II)-Zn(II) composite system and its environmental significance

The prevalence of struvite and other phosphate minerals in eutrophic environments has a significant effect on the transport and transformation of environmental heavy metals, but their competitive immobilization characteristics and mechanisms for heavy metals remain unclear. Three different sources of struvite (BS, CSHS, and CSS) were obtained respectively by biosynthesis and chemical synthesis with or without humic acid to investigate their competitive immobilization characteristics and mechanism of heavy metals in the Pb(II)-Cd(II)-Zn(II) composite system. The results showed that the immobilization of heavy metals by struvite is physico-chemical adsorption and the affinity (in descending order) is Pb(II) >> Cd(II)/Zn(II). Cd(II) promotes the immobilization of Pb(II)/Zn(II) by BS. The order of the selective strength by struvite for Pb(II) is BS >> CSS ≈ CSHS. The study indicates that the difference between struvite holding heavy metal ions is related to the material composition and heavy metal types, and BS shows best selective immobilization for Pb(II) in the Pb(II)-Cd(II)-Zn(II) composite system. This study provides a theoretical basis for understanding the environmental geochemical role and eco-environmental effects of struvite.

Revealing the mechanism of quartz sand seeding in accelerating phosphorus recovery from anaerobic fermentation supernatant through vivianite crystallization

The recovery of phosphorus (P) through vivianite crystallization offers a promising approach for resource utilization in wastewater treatment plants. However, this process encounters challenges in terms of small product size and low purity. The study aimed to assess the feasibility of using quartz sand as a seed material to enhance P recovery and vivianite crystal characteristics from anaerobic fermentation supernatant. Various factors, including seed dosage, seed size, Fe/P ratio, and pH, were systematically tested in batch experiments to assess their influence. Results demonstrated that the effect of seed enhancement on vivianite crystallization was more pronounced under higher seed dosages, smaller seed sizes, and lower pH or Fe/P ratio. The addition of seeds increased P recovery by 4.43% in the actual anaerobic fermentation supernatant and also augmented the average particle size of the recovered product from 19.57 to 39.28 μm. Moreover, introducing quartz sand as a seed material effectively reduced co-precipitation, leading to a notable 12.5% increase in the purity of the recovered vivianite compared to the non-seeded process. The formation of an ion adsorption layer on the surface of quartz sand facilitated crystal attachment and growth, significantly accelerating the vivianite crystallization rate and enhancing P recovery. The economic analysis focused on chemical costs further affirmed the economic viability of using quartz sand as a seed material for P recovery through vivianite crystallization, which provides valuable insights for future research and engineering applications.

Leaching of phosphorus from phosphate tailings and extraction of calcium phosphates: Toward comprehensive utilization of tailing resources

Phosphate tailing is an extremely fine by-product during phosphate ore flotation. Due to the large quantities and relatively higher P2O5 content, the phosphate tailings have been considered as a potential P resource, compared to other P-bearing wastes. Besides, phosphate tailings also contain a large amount of available components, such as Ca, Mg, and Si. To explore a low-cost and efficient process for the utilization of phosphate tailings, the hydrochloric acid leaching-precipitation method was employed to recover phosphorus. The P in phosphate tailings can be selectively dissolved into leaching liquor, followed by the precipitation of calcium phosphates from the leaching liquor through pH adjustment. The results showed that P was predominantly concentrated in fluorapatite and its dissolution ratio increased with the decrease in pH. At pH 1.0, the P dissolution efficiency from phosphate tailings reached 96.3%, along with the majority of Mg and Ca. However, Si was hardly dissolved. It demonstrated that almost all the fluorapatite and dolomite were dissolved while the quartz was difficult to dissolve. Dolomite was more preferentially dissolved than fluorapatite. Increasing temperature contributed to the dissolution of dolomite while suppressing fluorapatite dissolution. The residue containing 87.9% SiO2 (quartz) and only 0.25% P2O5 has the potential as a building material. As the pH increased to 7.0, the collected precipitate consisted of 34.18% P2O5 and 56.10% CaO, which can serve as a source of a slow-released phosphate fertilizer. The highly efficient utilization of phosphate tailings was achieved via this process.

A review of struvite crystallization for nutrient source recovery from wastewater

Nutrient recovery from wastewater not only reduces the nutrient load on water resources but also alleviates the environmental problems in aquatic ecosystems, which is a solution to achieve a sustainable society. Besides, struvite crystallization technology is considered a potential nutrient recovery technology because the precipitate obtained can be reused as a slow-release fertilizer. This review presents the basic properties of struvite and the theory of the basic crystallization process. In addition, the possible influencing variables of the struvite crystallization process on the recovery efficiency and product purity are also examined in detail. Then, the advanced auxiliary technologies for facilitating the struvite crystallization process are systematically discussed. Moreover, the economic and environmental benefits of the struvite crystallization process for nutrient recovery are introduced. Finally, the shortcomings and inadequacies of struvite crystallization technology are presented, and future research prospects are provided. This work serves as the foundation for the future use of struvite crystallization technology to recover nutrients in response to the increasingly serious environmental problems and resource depletion.

Source-oriented risks apportionment of toxic metals in river sediments of Bangladesh: a national wide application of PMF model and pollution indices

Intense human activities, particularly industrial and agricultural output, has enriched metal(loid)s in riverine sediment and endangered aquatic ecosystems and human health. Promoting proper river management requires an assessment of the possible ecological hazards and pollution posed by metal(loid)s in sediments. However, there are limited large-scale risk assessments of metal(loid)s contamination in riverine sediment in heavily populated nations like Bangladesh. This study compiled data on sediment metal(loid)s, for example, Cd, As, Cu, Ni, Cr, Pb, Mn, and Zn, from 24 major rivers located across Bangladesh between 2011 and 2022 and applied positive matrix factorization (PMF) to identify the critical metal(loid)s sources and PMF model-based ecological risks. Based on studied metal(loid)s, 12-78% of rivers posed higher contents than the upper continental crust and 8% of the river sediments for Cr and Ni, whereas 4% for Cd and As exceeded probable effect concentration. Cr and Ni in the sum of toxic units (STU), whereas Mn, As and Cd in potential ecological risk (PER) posed the highest contribution to contaminate sediments. In the studied rivers, sediment contaminant Mn derived from natural sources; Zn and Ni originated from mixed sources; Cr and Cu were released from the tannery and industrial emissions and Cd originated from agricultural practices. Source-based PER and NIRI indicated that mixed source (4% rivers) and tannery and industrial emission (4% rivers) posed very high risks in sediments. For the creation of macroscale policies and the restoration of contaminated rivers, our national-scale comprehensive study offers helpful references.

Efficient removal and recovery of phosphorus from industrial wastewater in the form of vivianite

With the shortage of phosphorus resources, the concept of phosphorus recovery from wastewater is generally proposed. Recently, phosphorus recovery from wastewater in the form of vivianite has been widely reported, which could be used as a slow-release fertilizer as well as the production of lithium iron phosphate for Li-ion batteries. In this study, chemical precipitation thermodynamic modeling was applied to evaluate the effect of solution factors on vivianite crystallization with actual phosphorus containing industrial wastewater. The modeling results showed that the solution pH influences the concentration of diverse ions, and the initial Fe²⁺ concentration affects the formation area of vivianite. The saturation index (SI) of vivianite increased with the initial Fe²⁺ concentration and Fe:P molar ratio. pH 7.0, initial Fe²⁺ concentration 500 mg/L and Fe:P molar ratio 1.50 were the optimal conditions for phosphorus recovery. Mineral Liberation Analyzer (MLA) accurately determined the purity of vivianite was 24.13%, indicating the feasibility of recovering vivianite from industrial wastewater. In addition, the cost analysis showed that the cost of recovering phosphorus by the vivianite process was 0.925 USD/kg P, which can produce high-value vivianite products and realize "turn waste into treasure".

Nicotine consumption rate through wastewater-based epidemiology: a systematic review, meta-analysis and probabilistic risk assessment

Wastewater-based epidemiology (WBE), as a rapid tool, is used to measure and monitor illicit drug consumption in the population. This method is also used to bridge biomarkers of exposure, contaminants, and human health. Smoking cigarettes and tobacco use are everyday habits in nowadays community. This systematic review and meta-analysis aimed to calculate nicotine consumption globally. The related studies were retrieved within international databases including Scopus, Google Scholar, and Web of Science, up to February 2021. It included twenty-one articles containing 87 measurements covering 275.3 million people with total wastewater samples of 2250. Results showed that the highest and lowest nicotine consumption rate (mg/1000 inh./day) was in Portugal (5860) and Vietnam (1201), respectively. The global pooled nicotine consumption rate was 2476 mg/1000 inh./day (95% CI (2289-2663). Based on WBE results, the average daily cigarette smoked per smoker is 14 (95% CI: 10-18 cigarettes/inh./day), close to the value of 14.2 reported by the survey and interview studies. Risk assessment of the nicotine consumption rate through WBE was calculated by the margin of exposure (MOE) approach. In total, 82% of nicotine consumption measurements were located in the "risk" level (MOE < 100), and 18% of the MOE values were between 100-1000. The results reveal that nicotine consumption risks need immediate global and local action strategies. Finally, these findings are helpful for healthcare agencies and policy-makers to take action against tobacco use prevalence.

Potential toxic elements in costal sediment of the Persian Gulf: a systematic review-meta-analysis, non-dietary risk assessment and ecological risk assessment

Potential toxic element (PTE) contamination in the Persian Gulf has become an important health concern in recent decades. This investigation aimed to meta-analyses of potential toxic elements including lead (Pb), inorganic arsenic (As), cadmium (Cd), nickel (Ni), and mercury (Hg) in the coastal sediment of the Persian Gulf. In this study, an attempt was made to retrieve papers conducted on the concentration of PTE in the coastal sediment of the Persian Gulf by searching in international databases including Web of Science, Scopus, Embase, and PubMed. Meta-analysis concentration of PTE in the coastal sediment of the Persian Gulf was conducted using random effects model based on the country subgroup. Additionally, non-dietary risk assessment including non-carcinogenic and carcinogenic risks from ingestion, inhalation and dermal contact routes and ecological risk assessment was estimated. Seventy-eight papers with 81 data-reports (1650 sample size) were included in our meta-analysis. The rank order of heavy metals in coastal sediment of the Persian Gulf based on pooled concentration was Ni (65.44 mg/kg) > Pb (58.35 mg/kg) > As (23.78 mg/kg) > Cd (1.75 mg/kg) > Hg (0.77 mg/kg). The highest concentration of As, Cd, Pb, Ni, and Hg was observed in the coastal sediment of Saudi Arabia, Arab Emirates, Qatar, Iran, and Saudi Arabia, respectively. Although the I_geo index in coastal sediment of the Persian Gulf was in grade 1 (uncontaminated) and grade 2 (slightly contaminated) but total target hazard quotient (TTHQ) of adults and adolescent was higher than 1 value in Iran, Saudi Arabic, United Arab Emirates, and Qatar. Total cancer risk (TCR) for adults and adolescent due to As was higher than 1E-6 in Iran, United Arab Emirates, and Qatar but TCR for adolescents due to As was higher than 1E-6 in Saudi Arabic. Therefore, it is recommended to monitor the concentration of PTE and implementation of programs to reduce the emission of PTE from resources in the Persian Gulf.

Progresses in lignin, cellulose, starch, chitosan, chitin, alginate, and gum/carbon nanotube (nano)composites for environmental applications: A review

Water sources are becoming increasingly scarce, and they are contaminated by industrial, residential, and agricultural waste-derived organic and inorganic contaminants. These contaminants may pollute the air, water, and soil in addition to invading the ecosystem. Because carbon nanotubes (CNTs) can undergo surface modification, they can combine with other substances to create nanocomposites (NCs), including biopolymers, metal nanoparticles, proteins, and metal oxides. Furthermore, biopolymers are significant classes of organic materials that are widely used for various applications. They have drawn attention due to their benefits such as environmental friendliness, availability, biocompatibility, safety, etc. As a result, the synthesis of a composite made of CNT and biopolymers can be very effective for a variety of applications, especially those involving the environment. In this review, we reported environmental applications (including removal of dyes, nitro compounds, hazardous materialsو toxic ions, etc.) of composites made of CNT and biopolymers such as lignin, cellulose, starch, chitosan, chitin, alginate, and gum. Also, the effect of different factors such as the medium pH, the pollutant concentration, temperature, and contact time on the adsorption capacity (AC) and the catalytic activity of the composite in the reduction or degradation of various pollutants has been systematically explained.

Synthesis and Characterization of Biodegradable Poly(vinyl alcohol)-Chitosan/Cellulose Hydrogel Beads for Efficient Removal of Pb(II), Cd(II), Zn(II), and Co(II) from Water

Globally, water contamination by heavy metals is a serious problem that affects the environment and human health. Adsorption is the most efficient way of water treatment for eliminating heavy metals. Various hydrogels have been prepared and used as adsorbents to remove heavy metals. By taking advantage of poly(vinyl alcohol) (PVA), chitosan (CS), cellulose (CE), and the process for physical crosslinking, we propose a simple method to prepare a PVA-CS/CE composite hydrogel adsorbent for the removal of Pb(II), Cd(II), Zn(II) and Co(II) from water. Structural analyses of the adsorbent were examined by Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy-energy dispersive X-ray (SEM-EDX) analysis, and X-ray diffraction (XRD). PVA-CS/CE hydrogel beads had a good spherical shape together with a robust structure and suitable functional groups for the adsorption of heavy metals. The effects of adsorption parameters such as pH, contact time, adsorbent dose, initial concentration of metal ions, and temperature on the adsorption capacity of PVA-CS/CE adsorbent were studied. The adsorption characteristics of PVA-CS/CE for heavy metals may be completely explained by pseudo-second-order adsorption and the Langmuir adsorption model. The removal efficiency of PVA-CS/CE adsorbent for Pb(II), Cd(II), Zn(II), and Co(II) was 99, 95, 92, and 84%, respectively, within 60 min. The heavy metal's hydrated ionic radius may be crucial in determining the adsorption preference. After five consecutive adsorption-desorption cycles, the removal efficiency remained over 80%. As a result, the outstanding adsorption-desorption properties of PVA-CS/CE can potentially be extended to industrial wastewater for heavy metal ion removal.

Phenol red dye removal from wastewater using TiO2-FSM-16 and Ni-FSM-16 photocatalysts

In this study, the performance of Ni-FSM-16 and TiO₂-FSM-16 photocatalysts in phenol red removal was explored. The XRD, FE-SEM, and BET tests were used to characterize the catalysts. All experiments were performed at ambient temperature and under UV (20 W). The parameters including dye concentration (20-80 mg/L), photocatalyst concentration (0-8 g/L), UV exposure duration, and contact time (0-160 min) were optimized using RSM software. BET values of Ni-FSM-16 and TiO₂-FSM-16 were 718.63 m²/g and 844.93 m²/g, respectively. TiO₂-FSM-16 showed better performance in dye removal than Ni-FSM-16. At pH 3, the maximum dye removal by TiO₂-FSM-16/UV and Ni-FSM-16/UV was obtained 87% and 64%, respectively. The positive hole species had the main role in photocatalytic phenol red removal. The reusability study was done for up to 7 cycles, but the catalysts can be reused effectively for up to 3 cycles. The synergistic factor for the TiO₂-FSM-16 and TiO₂-FSM-16/UV processes were calculated to be 1.55 and 2.12, respectively. The dye removal efficiency by TiO₂-carbon and Ni-carbon was slightly lower than those obtained by the FSM-16 ones. The TiO₂-FSM-16 and Ni-FSM-16 catalysts had a suitable surface and acceptable efficiency in phenol red removal.

Assessment of graphene-based polymers for sustainable wastewater treatment: Development of a soft computing approach

Since graphene possesses distinct electrical and material properties that could improve material performance, there is currently a growing demand for graphene-based electronics and applications. Numerous potential applications for graphene include lightweight and high-strength polymeric composite materials. Due to its structural qualities, which include low thickness and compact 2D dimensions, it has also been recognized as a promising nanomaterial for water-barrier applications. For barrier polymer applications, it is usually applied using two main strategies. The first is the application of graphene, graphene oxide (GO), and reduced graphene oxide (rGO) to polymeric substrates through transfer or coating. In the second method, fully exfoliated GO or rGO is integrated into the material. This study provides an overview of the most recent findings from research on the use of graphene in the context of water-barrier applications. The advantages and current limits of graphene-based composites are compared with those of other nanomaterials utilized for barrier purposes in order to emphasize difficult challenges for future study and prospective applications.

On the removal efficiency of copper ions in wastewater using calcined waste eggshells as natural adsorbents

Eggshells offer many advantages as adsorbents, such as affordability without special preparations other than pulverization and calcination. However, the manufacturing industry generally has a severe problem with high concentrations of heavy metals in wastewater. The purpose of this study was to use eggshell byproducts and calcined eggshell treatment for the adsorption of copper in an aqueous solution. The reaction time, metal concentration, adsorbent dose, temperature, and pH were evaluated using primary factors followed by the response surface method (RSM) to investigate the optimum conditions for eggshell byproducts and calcined eggshell adsorption treatment. The results of the one-factor-at-a-time experiment showed that the optimal adsorption rate was obtained from treatment at 24 h, 25 mg/L, 10 mg, and 25 °C. In addition, the effect of pH on the adsorption rates of eggshells and eggshells with membrane were detected at pH values of 5 and 5.9 and found to be 95.2, 90.5, and 73.3%. The reaction surface experiment showed that the best adsorption rate reached 99.3% after calcination at 900 °C for 2 h and a 20 min reaction. The results showed that eggshells, eggshell membranes, eggshells with membrane, and calcined eggshells could be applied to remove copper ions from industrial wastewater. The adsorption capacity of the calcined eggshell is better than that of the non-calcined eggshell and has good neutrality in acidic industrial wastewater. Therefore, it is convenient and practical for practical production and application. Likewise, this study conveys promising findings in the context of improving wastewater treatment based on a circular economy approach to waste reuse in the food industry and represents a valuable direction for future research.

Bamboo Nanocellulose/Montmorillonite Nanosheets/Polyethyleneimine Gel Adsorbent for Methylene Blue and Cu(II) Removal from Aqueous Solutions

In recent years, the scarcity of pure water resources has received a lot of attention from society because of the increasing amount of pollution from industrial waste. It is very important to use low-cost adsorbents with high-adsorption performance to reduce water pollution. In this work, a gel adsorbent with a high-adsorption performance on methylene blue (MB) and Cu(II) was prepared from bamboo nanocellulose (BCNF) (derived from waste bamboo paper) and montmorillonite nanosheet (MMTNS) cross-linked by polyethyleneimine (PEI). The resulting gel adsorbent was characterized by Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (SEM), X-ray photoelectron spectroscopic (XPS), etc. The results indicated that the MB and Cu(II) adsorption capacities of the resulting gel adsorbent increased with the solution pH, contact time, initial concentration, and temperature before equilibrium. The adsorption processes of MB and Cu(II) fitted well with the fractal-like pseudo-second-order model. The maximal adsorption capacities on MB and Cu(II) calculated by the Sips model were 361.9 and 254.6 mg/g, respectively. The removal of MB and Cu(II) from aqueous solutions mainly included electrostatic attraction, ion exchange, hydrogen bonding interaction, etc. These results suggest that the resulting gel adsorbent is an ideal material for the removal of MB and Cu(II) from aqueous solutions.

Spatial green growth in China: exploring the positive role of investment in the treatment of industrial pollution

The industrial sector of China is critical to the country's economic growth. On the other side, industrialisation has resulted in a high rate of emissions, pushing China to spend extensively on industrial pollution remediation. As a result, this study looks at the relationship between investment completed in the treatment of industrial pollution and economic development. Initially, the study used the global Moran's I test (Queen's contiguity matrix) to find spatial autocorrelation for the 'investment completed in the treatment of industrial pollution' factor, where the study found a positive association across Chinese provinces, and suggest the existence of spatial autocorrelation. Thereafter, a time-fixed effect spatial error model was used due to the lowest Akaike information criterion and Bayesian information criterion to analyse regional data of China from 1999 to 2018. The data reveal a positive association between investment completed in the treatment of industrial pollution and regional economic growth, both in the short and long term. Furthermore, the negative consequences of urban wages and foreign investment on investment completed in the treatment of industrial pollution are having the reverse effect on regional green development, necessitating ecologically friendly actions to mitigate the negative environmental effects of both. The results highlight the need for policymakers in other countries to review their plans for economic expansion and create environmentally friendly legislation. By implementing the Chinese green economic growth model, policymakers in industrially polluting nations can reduce industrial pollution and foster green growth in their nation.

Application of nano remediation of mine polluted in acid mine drainage water using machine learning model

Acid mine drainage (AMD) is the term used to describe drainage from coal mines with high sulfur-bearing rocks. The oxidative weathering of metal sulfides leads to AMD. The acidic environment corrodes more harmful compounds in the soil, which is spread throughout the working area. One such significant metal is copper, which is extracted in massive quantities from ores rich in sulfide. A copper-extraction resin might be created by combining diatomaceous earth (DE) particles with polyethyleneimine (PEI), which is shown to have great selectivity and affinity for copper. In this effort, PEI-DE particles' copper absorption level was examined by using synthetic and actual acid mine drainage samples at varied pH values. The findings of the copper uptake particles have been examined through the Support Vector Machine (SVM) model. Using the n-fold 14 cross-validation approach, the quantities of parameters and C are estimated to be 0.001 and 0.01, respectively. The SVM analysis was correct, and the findings indicated that copper could bind to the material efficiently and preferentially at pH 4. Subsequent water elution studies at a pH value of 1 confirmed the pH-reliant interaction between dissolved Cu and PEI by demonstrating full release of the adsorbed Cu. In this research, the copper absorption of PEI-DE particles from synthetic and genuine AMD specimens was studied based on several pH conditions. The findings suggest that copper may attach to the material effectively and preferentially at pH 4. Studies of filtering water at pH1 later confirmed that all of the adsorbed Cu was released. This shows that the interaction between PEI and dissolved Cu depends on PH.

Improved neural network with least square support vector machine for wastewater treatment process

This research offers a unique interval by using the predicting approach for discharge indicators of water quality data such as biochemical oxygen demand (BOD) and ammonia nitrogen (NH3-N). This is considered one of the significant quality metrics in wastewater treatment plants for water quality management as well as surveillance. To begin, the effluent information for BOD/NH3-N and their supplementary parameters are gathered. Hence BOD and NH3 are considered major feature sources for estimating water pollutants. BOD is high then oxygen level is very low in the water due to pollutants or algae. Ammonia nitrogen is an organic waste component in water from sewage. The significant characteristics with good correlation levels of BOD and NH3-N are examined and identified using a grey correlation analysis method after certain basic data pre-processing procedures. The BOD/NH3-N effluent information of a water treatment plant is predicted using an upgraded feed-forward neural network with the least square support vector machine (FFNN-LSSVM) method. An optimization approach for an enhanced feed-forward neural network (IFFNN) is built by Machine Learning Algorithms. The IFFNN used regular influent water quality, influent rate of flow, and Wastewater performance monitoring and operational conditions as input parameters. For future prediction, input variables were previous different wastewater quality measurements. Lastly, the analysis shows that, when compared to other current algorithms, the proposed methodology can forecast wastewater quality of water with high accuracy in predicting BOD and NH3 levels, limited computation duration, mean error less than 10% and R² is 90% proves better than existing techniques.

Insights into the Synergistic Removal of Copper(II), Cadmium(II), and Chromium(III) Ions Using Modified Chitosan Based on Schiff Bases-g-poly(acrylonitrile)

Chitosan has received broad consideration as an adsorbent for all pollutants because of its low cost and great adsorption potential. However, its shortcomings, including sensitivity to pH, poor thermal stability, and poor mechanical strength, limit its use. The functional groups of chitosan can be modified to enhance its performance by the grafting technique and Schiff base modification. The grafting process used acrylonitrile (Ch-g-PAN) as a monomer and potassium persulfate as an initiator. After that, the modification via preparation of the Schiff base reaction using salicylaldehyde (Ch-g-Sch I) and P-anisaldehyde (Ch-g-Sch II) was carried out. The synthesized copolymers were detailed and characterized through several spectroscopic and microscopic techniques including infrared spectroscopy, scanning electron microscopy, and X-ray diffraction. In addition, Ch-g-Sch I and Ch-g-Sch II were applied in the removal of different metal ions such as Cu²⁺, Cd²⁺, and Cr³⁺. The maximum adsorption capacity of Ch-g-Sch I for Cd²⁺ was 183.7 mg g^-1 in 24 h, while in the case of Ch-g-Sch II, the maximum adsorption capacity for Cd²⁺ was improved to 322.9 mg g^-1 for the same time. Moreover, adsorption thermodynamic analysis displays that the all ion adsorption process was not random and the pseudo-second-order model fitted with experimental results. Finally, Ch-g-Sch I and Ch-g-Sch II were applied as designs for industrial wastewater treatment with significant efficiency.

The concentration of potentially toxic elements (PTEs) in the coffee products: a systematic review and meta-analysis

Coffee is one of the most consumed products globally, and its contamination with potentially toxic elements (PTEs) occurs throughout the production chain and production. Therefore, the current meta-analysis study aimed to estimate the concentration of essential elements (Cu and Co) and the contamination of PTEs (Ni, Cr, Pb, As, and Cd) in coffee. The recommended databases, including PubMed, Scopus, and ScienceDirect, were investigated to collect data regarding the contamination of PTEs in coffee products from 2010 to 2021. Among 644 retrieved citations in the identification step, 34 articles were included in the meta-analysis. The pooled mean concentration of essential elements in coffee products is much higher than that of toxic elements (Co (447.106 µg/kg, 95% CI: 445.695-448.518 µg/kg) > Ni (324.175 µg/kg, 95% CI: 322.072-326.278 µg/kg) > Cu (136.171 µg/kg, 95% CI: 134.840-137.503 µg/kg) > Cr (106.865 µg/kg, 95% CI: 105.309-108.421 µg/kg) > Pb (21.027 µg/kg, 95% CI: 20.824-21.231 µg/kg) > As (3.158 µg/kg, 95% CI: 3.097-3.219 µg/kg) > Cd (0.308 µg/kg; 95% CI: 0.284-0.332 µg/kg)). Results showed high differences between pooled concentrations of all PTEs in coffee products of different countries.

Synthesis characterization of Zn-based MOF and their application in degradation of water contaminants

Metal-organic frameworks (MOFs) are currently popular porous materials with research and application value in various fields such as medicine and engineering. Aiming at the application of MOFs in photocatalysis, this paper mainly reviews the main synthesis methods of ZnMOFs and the latest research progress of Zn MOF-based photocatalysts to degrade organic pollutants in water, such as organic dyes. This nanomaterial is being used to treat wastewater and has proven to be very efficient because of its exceptionally large surface area and porous nature. The results show that Zn-MOFs are capable of high degradation of the above pollutants and over 90% of degradation was observed in publications. In addition, the reusability percentage was examined and studies showed that the Zn-MOF nanostructure has very good stability and can continue to degrade a high percentage of pollutants after several cycles. This review focuses on Zn-MOFs and their composites. First, the methods of synthesis and characterization of these compounds are given. Finally, the application of these composites in the process of photocatalytic degradation of dye pollutants such as methylene blue, methyl orange, crystal violet, rhodamine B, etc. is explained.

High Purity Struvite Recovery from Hydrothermally-Treated Sludge Supernatant Using Magnetic Zirconia Adsorbent

Recovery of phosphorus from sludge will help to alleviate the phosphorus resource crisis. However, the release of phosphorus from sludge is accompanied by the leaching of large amounts of coexisting ions, i.e., Fe, Al, Ca, and organic matter, which decreases the purity of sludge-derived products. In this study, an adsorption-desorption process using magnetic zirconia (MZ) as the adsorbent is proposed to obtain a high purity recovery product. The process involves selective adsorption of phosphate from the hydrothermally treated sludge supernatant (HTSS) using MZ, followed by desorption and precipitation to obtain the final product: struvite. The results indicated that at a dosage of 15 g/L, more than 95% of phosphorus in the HTSS could be adsorbed by MZ. Coexisting ions (Ca²⁺, Mg²⁺, Fe³⁺, Al³⁺, SO₄^2-, NO₃^-, Cl^-, etc.) and organic matter (substances similar to fulvic and humic acid) in the HTSS had a limited inhibitory effect on phosphate adsorption. Using a binary desorption agent (0.1 mol/L NaOH + 1 mol/L NaCl), 90% of the adsorbed phosphorus could be desorbed. Though adsorption-desorption treatment, struvite purity of the precipitated product increased from 41.3% to 91.2%. Additionally, MZ showed good reusability, maintaining a >75% capacity after five cycles. X-ray photoelectron spectroscopy (XPS) indicated that MZ adsorbed phosphate mainly by inner-sphere complexation. This study provided a feasible approach for the recovery of phosphorus from sludge with high purity.

Recent Progress in Photocatalytic Removal of Environmental Pollution Hazards in Water Using Nanostructured Materials

Water pollution has become a critical issue because of the Industrial Revolution, growing populations, extended droughts, and climate change. Therefore, advanced technologies for wastewater remediation are urgently needed. Water contaminants are generally classified as microorganisms and inorganic/organic pollutants. Inorganic pollutants are toxic and some of them are carcinogenic materials, such as cadmium, arsenic, chromium, cadmium, lead, and mercury. Organic pollutants are contained in various materials, including organic dyes, pesticides, personal care products, detergents, and industrial organic wastes. Nanostructured materials could be potential candidates for photocatalytic reduction and for photodegradation of organic pollutants in wastewater since they have unique physical, chemical, and optical properties. Enhanced photocatalytic performance of nanostructured semiconductors can be achieved using numerous techniques; nanostructured semiconductors can be doped with different species, transition metals, noble metals or nonmetals, or a luminescence agent. Furthermore, another technique to enhance the photocatalytic performance of nanostructured semiconductors is doping with materials that have a narrow band gap. Nanostructure modification, surface engineering, and heterojunction/homojunction production all take significant time and effort. In this review, I report on the synthesis and characterization of nanostructured materials, and we discuss the photocatalytic performance of these nanostructured materials in reducing environmental pollutants.

A Cu(ii) complex supported on Fe3O4@SiO2 as a magnetic heterogeneous catalyst for the reduction of environmental pollutants

Today, the presence of pollutants in the environment has become one of the serious problems and concerns of human beings. To eliminate these pollutants, researchers have made many efforts. One of the most important of these efforts is the reduction of such contaminants in the presence of effective catalysts. Two of the most important and widespread types of these pollutants are nitro compounds and organic dyes. In this paper, we report the synthesis of an efficient and reusable magnetic catalyst using Fe3O4@SiO2 core-shell nanoparticles (NPs), N-(4-bromophenyl)-N'-benzoylthiourea, and copper(ii). Specifically, the Cu(ii)-N-(4-bromophenyl)-N'-benzoylthiourea complex supported on Fe3O4-core magnetic NPs (CM)/SiO2-shell (SS) (CM@SS-BBTU-Cu(ii)) has been prepared. CM@SS-BBTU-Cu(ii) was characterized by FT-IR (Fourier transform infrared spectroscopy), XRD (X-ray diffraction), TEM (transmission electron microscopy), HRTEM (high resolution transmission electron microscopy), FFT (fast Fourier transform), VSM (vibrating sample magnetometry), TG-DTA (thermogravimetry-differential thermal analysis), STEM (scanning transmission electron microscopy), EDS (energy-dispersive X-ray spectroscopy), and elemental mapping. The synthesized CM@SS-BBTU-Cu(ii) was applied for the reduction of 4-nitrophenol (4-NP), Congo red (CR), and methylene blue (MB) in the presence of NaBH4 (sodium borohydride) at room temperature. CM@SS-BBTU-Cu(ii) can be recycled and reused 5 times. Our results displayed that the performance of the catalyst was not significantly reduced by recycling.

A novel fluorescent "OFF-ON" sensing strategy for Hg (II) in water based on functionalized gold nanoparticles

Mercury ion (Hg²⁺) is a heavy metal pollutant that can affect the safety of water environment and endanger human health. A novel detection strategy (GNPs-_L-Cys-Rh6G2) for Hg²⁺ based on a fluorescence "OFF-ON" was proposed. Gold nanoparticles (GNPs) were assembled with _l-cysteine (_L-Cys), which was used as a "bridge" to link with rhodamine 6G derivatives (Rh6G2). The fluorescence state transition of GNPs-_L-Cys-Rh6G2 switching from "OFF"-"ON" was observed because Hg²⁺ opened the spirolactam ring through a catalytic hydrolysis mechanism. The fluorescence signal of the GNPs-_L-Cys-Rh6G2 system mixed with Hg²⁺ in the concentration range of 10-100 μM was analyzed and determined with a limit of detection (LOD) of 2 μM (S/N = 3). Moreover, the spiked Hg²⁺ concentration in real water samples were successfully quantified by GNPs-_L-Cys-Rh6G2, which was in line with the ideal average recovery rate and relative standard deviation. The proposed strategy exhibited high specificity, sensitivity and stability, providing a novel sensing platform for heavy metal ions detection in water environment.

Biochar-seeded struvite precipitation for simultaneous nutrient recovery and chemical oxygen demand removal in leachate: From laboratory to pilot scale

Refuse transfer station (RTS) leachate treatment call for efficient methods to increase nutrient recovery (NH4+−N and PO43−−P) and chemical oxygen demand (COD) removal. In this study, the effects of various operational factors (seeding dose, pH, initial NH4+-N concentration, and reaction time) on biochar-seeded struvite precipitation were investigated at laboratory and pilot scales. Mealworm frass biochar (MFB) and corn stover biochar (CSB) were used as seeding materials to compare with traditional seed struvite. The maximum NH4+−N and PO43−−P recover efficiency of the MFB-seeded process reached 85.4 and 97.5%, higher than non-seeded (78.5 and 88.0%) and CSB-seeded (80.5 and 92.0%) processes and close to the struvite-seeded (84.5 and 95.1%) process. The MFB-seeded process also exhibited higher COD removal capacity (46.4%) compared to CSB-seeded (35.9%) and struvite-seeded (31.2%) processes and increased the average particle size of the struvite product from 33.7 to 70.2 μm for better sustained release. XRD, FT-IR, and SEM confirmed the orthorhombic crystal structure with organic matter attached to the struvite product. A pilot-scale test was further carried out in a custom-designed stirred tank reactor (20 L). In the pilot-scale test, the MFB-seeded process still spectacularly recovered 77.9% of NH4+−N and 96.1% of PO43−−P with 42.1% COD removal, which was slightly lower than the laboratory test due to insufficient and uniform agitation. On the whole, MFB-seeded struvite precipitation is considered to be a promising pretreatment method for rural RTS leachate.

Performance Comparison of EGSB and IC Reactors for Treating High-Salt Fatty Acid Organic Production Wastewater

This study used the EGSB and IC reactors to treat the high-salt and high-concentration organic wastewater (high-salt fatty acid production wastewater) and compared their performances The experimental results showed that the optimal influent water quality thresholds for both bioreactors to treat this wastewater were a COD concentration of 18,000 mg/L and a sulfate ion concentration of about 8000 mg/L. The reactor operated well when C/S was greater than 2.8. In addition, the value of C/S should not be less than 1.5. This is due to that under this condition, the sulfate reduction process has a significant impact on the removal of COD, and MPB may be inhibited by sulfides. The organic load OLR should not be greater than 10 kgCOD/(m3·d). It was also found that the start-up time of the IC reactor with external circulation was slightly shorter, and the COD removal effect, gas production rate, and load tolerance were slightly better than those of the EGSB reactor, the best reflux ratio of the two reactors was 6:1. The appropriate rising flow rate was 0.4 m/h.

Impact of catalytic hydrothermal treatment and Ca/Al-modified hydrochar on lability, sorption, and speciation of phosphorus in swine manure: Microscopic and spectroscopic investigations

The effects of catalytic hydrothermal (HT) pretreatment on animal manure followed by the addition of hydrochar on the nutrients recovery have not yet been investigated using a combination of chemical, microscopic, and spectroscopic techniques. Therefore, a catalytic HT process was employed to pretreat swine manure without additives (manure-HT) and with H₂O₂ addition (manure-HT- H₂O₂) to improve the conversion efficiency of labile or organic phosphorus (P) to inorganic phase. Then, a Ca-Al layered double hydroxide hydrochar (Ca/Al LDH@HC) derived from corn cob biomass was synthesized and applied to enhance P sorption. Scanning electron microscopy (SEM), and three-dimensional excitation emission matrix (3D-EEM), X-ray photoelectron spectroscopy (XPS), P k-edge X-ray absorption near edge structure (XANES), were used to elucidate the mechanisms of P release and capture. The H₂O₂ assisted HT treatment significantly enhanced the release of inorganic P (251.4 mg/L) as compared to the untreated manure (57.2 mg/L). The 3D-EEM analysis indicated that the labile or organic P was transformed and solubilized efficiently along with the deconstruction of manure components after the H₂O₂ assisted HT pretreatment. Application of Ca/Al LDH@HC improved the removal efficiency of P from the derived P-rich HT liquid. This sorption process was conformed to the pseudo-second-order model, suggesting that chemisorption was the primary mechanism. The results of SEM and P k-edge XANES exhibited that Ca, as the dominated metal component, could act as a reaction site for the formation of phosphate precipitation. These results provide critical findings about recovering P from manure waste, which is useful for biowastes management and nutrients utilization, and mitigating unintended P loss and potential environmental risks.

Ultrasonic-assisted synthesis of zeolite/activated carbon@MnO2 composite as a novel adsorbent for treatment of wastewater containing methylene blue and brilliant blue

In this study, zeolite/activated carbon@MnO₂ composite was used as a novel adsorbent to eliminate methylene blue (MB) and brilliant blue (BB) dyes from aqueous media. To this end, activated carbon (AC) was produced by Ziziphus Spina-Christi leaves and then used to synthesize zeolite/AC@MnO₂ composite. Various analyses such as BET, SEM, EDX, Map, FTIR, and XRD were performed to determine the surface features of the above composite. BET analysis indicated that the aforementioned composite has a mesoporous structure. Also, the best conditions for the adsorption of MB and BB dyes were obtained at pH of 9 and 2, temperature of 25 °C, adsorbent dosage of 1 and 2 g/L, initial dye concentration of 10 mg/L, and contact time of 40 and 60 min, respectively. Under optimal conditions, the utmost removal efficiency of MB and BB dyes using the zeolite/AC@MnO₂ composite was 98.43% and 96.54%, respectively, indicating significant adsorption efficiencies. Moreover, the utmost adsorption capacity of MB and BB dyes was 67.56 and 66.22 mg/g, respectively. Furthermore, intraparticle and film diffusion mechanisms were very important in the adsorption process. Besides, thermodynamic and equilibrium studies indicated that the adsorption process is exothermic, physical, and spontaneous. Generally, the aforementioned composite has a significant adsorption capacity and can be a suitable adsorbent to eliminate cationic dyes from industrial effluents.

Biowaste- and nature-derived (nano)materials: Biosynthesis, stability and environmental applications

Due to the environmental pollution issues and the supply of drinking/clean water, removal of both inorganic and organic (particularly dyes, nitroarenes, and heavy metals) to non-dangerous products and useful compounds are very important transformations. The deployment of sustainable and eco-friendly nanomaterials with exceptional structural and unique features such as high efficiency and stability/recyclability, high surface/volume ratio, low-cost production routes has become a priority; nonetheless, numerous significant challenges/restrictions still remained unresolved. The immobilization of green synthesized metal nanoparticles (NPs) on the natural materials and biowaste generated templates have been analyzed widely as a greener approach due to their environmentally friendly preparation methods, earth-abundance, cost-effectiveness with low energy consumption, biocompatibility, as well as adjustability in various cases of biomolecules as bioreducing agents. Natural and biowaste materials are widely considered as important sources to fabricate greener and biosynthesized types of metal, metal oxide, and metal sulfide nanomaterials using plant extracts. Integrating green synthesized nanoparticles with various biotemplates offers new practical composites for mitigating environmental challenges. In this review, degradation of dyes, reduction of toxic nitrophenols, absorption of heavy metals, and other hazardous/toxic environmental pollutants from contaminated water bodies using biowaste- and nature-derived nanomaterials are highlighted.

Study on the Removal Efficiency and Mechanism of Tetracycline in Water Using Biochar and Magnetic Biochar

In this study, a new type of sludge-derived biochar material with high tetracycline removal efficiency, named magnetic Fe3O4 biochar, was accomplished by KOH activated and loaded with magnetic Fe3O4. The particles with spherical pellets observed by SEM, as well as the XRD patterns, indicated that magnetic Fe3O4 nanoparticles were successfully loaded onto the biochar. We studied the adsorption effects and mechanisms of the following three different adsorption materials for tetracycline: biochar (BC), magnetic Fe3O4, and magnetic biochar (MBC), and the loading conditions and reusability of the materials were also considered. The adsorption effects were as follows: Fe3O4 (94.3%) > MBC (88.3%) > BC (65.7%), and the ratio of biochar to ferric salt was 0.2:1; the removal effect reached the best result. Under an acidic condition, the adsorption capacity of all the materials reached the maximum, and the adsorption of tetracycline in water, by three adsorbents, involves chemical adsorption as the leading process and physical adsorption as the auxiliary process. Various characterizations indicated the removal of tetracycline, including pore filling, electrostatic interaction, hydrogen bond action, and cationic-π action. Complex bridging is a unique adsorption mechanism of magnetic Fe3O4 and magnetic biochar. In addition, the magnetic biochar also possesses π–π bond interaction. The magnetic materials can still maintain a certain amount of adsorption capacity on tetracycline after five cycles. This study proved that the magnetic sludge-based biochar are ideal adsorbents for the removal of tetracycline from water, as well as an effective route for the reclamation of waste sludge.

Phosphorous and Silica Recovery from Rice Husk Poultry Litter Ash: A Sustainability Analysis Using a Zero-Waste Approach

Phosphate rocks are a critical resource for the European Union, and alternative sources to assure the future production of a new generation of fertilizers are to be assessed. In this study, a statistical approach, combined with a sustainability evaluation for the recovery of materials from waste containing phosphorus (P), is presented. This work proposes a strategy to recover P and silica (SiO2) from rice husk poultry litter ash (RHPLA). The design of experiment (DoE) method was applied to maximize the P extraction using hydrochloric acid (HCl), with the aim to minimize the contamination that can occur by leachable heavy metals present in RHPLA, such as zinc (Zn). Two independent variables, the molar concentration of the acid, and the liquid-to-solid ratio (L/S) between the acid and RHPLA, were used in the experimental design to optimize the operating parameters. The statistical analysis showed that a HCl concentration of 0.34 mol/L and an L/S ratio of 50 are the best conditions to recover P with low Zn contamination. Concerning the SiO2, its content in RHPLA is too low to consider the proposed recovery process as advantageous. However, based on our analysis, this process should be sustainable to recover SiO2 when its content in the starting materials is more than 80%.