Physical-chemical interactions between pharmaceuticals and biochar in synthetic and real urine

Comparing the adsorption of micropollutants on activated carbon from anaerobically stored, organics-depleted, and nitrified urine

Separate collection and treatment of urine optimizes nutrient recovery and enhances micropollutant removal from municipal wastewater. One typical urine treatment train includes nutrient recovery in three biological processes: anaerobic storage, followed by aerobic organics degradation concurrently with nitrification. These are usually followed by activated carbon adsorption to remove micropollutants. However, removing micropollutants prior to nitrification would protect nitrifiers from potential inhibition by pharmaceuticals. In addition, combining simplified biological treatment with activated carbon adsorption could offer a cheap and robust process for removing micropollutants where nutrient recovery is not the first priority, as a partial loss of ammonia occurs without nitrification. In this study, we investigated whether activated carbon adsorption could also take place between the three biological treatment steps. We tested the effectiveness of micropollutant removal with activated carbon after each biological treatment step by conducting experiments with anaerobically stored urine, organics-depleted urine, and nitrified urine. The urine solutions were spiked with 19 pharmaceuticals: amisulpride, atenolol, atenolol acid, candesartan, carbamazepine, citalopram, clarithromycin, darunavir, diclofenac, emtricitabine, fexofenadine, hydrochlorothiazide, irbesartan, lidocaine, metoprolol, N4-acetylsulfamethoxazole, sulfamethoxazole, trimethoprim, venlafaxine, and two artificial sweeteners, acesulfame and sucralose. Batch experiments were conducted with powdered activated carbon (PAC) to determine how much activated carbon achieve which degree of micropollutant removal and how organics, pH, and speciation change from ammonium to nitrate influence adsorption. Micropollutant removal was also tested in granular activated carbon (GAC) columns, which is the preferred technology for micropollutant removal from urine. The carbon usage rates (CUR) per person were lower for all urine solutions than for municipal wastewater. The results showed that organics depletion would be needed when micropollutant removal was the sole aim of urine treatment, as the degradation of easily biodegradable organics prevented clogging of GAC columns. However, CUR did hardly improve with organics-depleted urine compared to stored urine. The lowest CUR was achieved with nitrified urine. This resulted from the additional organics removal during nitrification and not the lower pH or the partial conversion of ammonium to nitrate. In addition, we showed that the relative pharmaceutical removal in all solutions was independent of the initial pharmaceutical concentration unless the background organics matrix changed considerably. We conclude that removal of micropollutants in GAC columns from organics-depleted urine can be performed without clogging, but with the drawback of a higher carbon usage compared to removal from nitrified urine.

Selective degradation of endogenous organic metabolites in acidified fresh human urine using sulphate radical-based advanced oxidation

The human urine metabolome is complex, containing a wide range of organic metabolites that affect treatment of urine collected in resource-oriented sanitation systems. In this study, an advanced oxidation process involving heat-activated peroxydisulphate was used to selectively oxidise organic metabolites in urine over urea and chloride. Initial experiments evaluated optimal conditions (peroxydisulphate dose, temperature, time, pH) for activation of peroxydisulphate in unconcentrated, non-hydrolysed synthetic urine and real urine acidified to pH 3.0. Subsequent experiments determined the fate of 268 endogenous organic metabolites (OMs) and removal of COD from unconcentrated and concentrated real urine (80-90% mass reduced by evaporation). The results revealed >90% activation of 60 mM peroxydisulphate in real unconcentrated urine heated to 90 °C for 1 h, resulting in 43% ΣOMs degradation, 22% COD removal and 56% total organic carbon removal, while >94% of total nitrogen and >97% of urea in real unconcentrated urine were recovered. The mechanism of urea degradation was identified to be chemical hydrolysis to ammonia, with the rate constant for this reaction determined to be 1.9 × 10-6 s-1 at pH 3.0 and 90 °C. Treating concentrated real urine resulted in similar removal of COD, ΣOMs degradation and total nitrogen loss as observed for unconcentrated urine, but with significantly higher chloride oxidation and chemical hydrolysis of urea. Targeted metabolomic analysis revealed that peroxydisulphate treatment degraded 157 organic metabolites in urine, of which 67 metabolites were degraded by >80%. The rate constant for the reaction of sulphate radicals with oxidisable endogenous organic metabolites in urine was estimated to exceed 108 M-1 s-1. These metabolites were preferentially oxidised over chloride and urea in acidified, non-hydrolysed urine treated with peroxydisulphate. Overall, the findings support the development of emerging urine recycling technologies, including alkaline/acid dehydration and reverse osmosis, where the presence of endogenous organic urine metabolites significantly influences treatment parameters such as energy demand and product purity.

Optimization of pig manure-derived biochar for ammonium and phosphate simultaneous recovery from livestock wastewater

Livestock wastewater has led to serious eco-environmental issues. To effectively treat livestock wastewater and realize the resource utilization of livestock solid waste, manure waste has been widely used to prepare biochar for the recovery of nitrogen and phosphorus. However, fresh biochar has a poor ability to adsorb phosphate due to its negative charge. To overcome the defect, the proportion of biochar samples prepared at 400 °C and 700 °C was optimized under a mass ratio of 2:3 to obtain mixed biochar PM 4-7, achieving the purpose of enhanced ammonium and phosphate recovery in livestock wastewater simultaneously without any modification. The effects of pyrolysis temperature, dosage, and pH were studied, different adsorption models were used to explore the adsorption mechanism, and the effect of biochar loaded with nutrient elements on seed was verified through a seed germination experiment. It was revealed that the maximum removal rates of phosphate and ammonium were 33.88 % and 41.50 %, respectively, endorsing that mixed biochar PM 4-7 can recover nutrients from livestock wastewater, and could be used as a slow-release fertilizer to promote seed germination and growth. This method provides a new potential way for the efficient resource utilization of pig manure and the recovery of nutrients from breeding wastewater.

Competitive adsorption characteristics of gasoline evaporated VOCs in microporous activated carbon by molecular simulation

The activated carbon in the vehicle's carbon canister needs to adsorb a variety of VOCs (Volatile Organic Compounds) emitted by gasoline evaporation, while the difference in gas adsorption capacity can lead to adsorption competition phenomena. In this study, three typical VOCs (toluene, cyclohexane, and ethanol) were selected to study the adsorption competition characteristics between multi-component gases at different pressures by molecular simulation method. In addition, the effect of temperature on adsorption competition was also investigated. The results show that the selectivity of activated carbon to toluene is negatively correlated with the adsorption pressure, but the opposite is true for ethanol, and the change of cyclohexane is not significant. The competitive order of the three VOCs is toluene > cyclohexane > ethanol at low pressure, which becomes ethanol > toluene > cyclohexane at high pressure. With increasing pressure, the interaction energy decreases from 12.87 kcal/mol to 11.87 kcal/mol, where the electrostatic interaction energy increases from 1.97 kcal/mol to 2.54 kcal/mol. In microporous activated carbon, the competition is mainly manifested in that ethanol preempts the low-energy adsorption sites of toluene in the pore size of 10 Å to 18 Å, while gas molecules near the surface of activated carbon or in smaller pore sizes are stably adsorbed without competition. Despite the fact that high temperature decreases the total adsorption capacity, activated carbon selectivity for toluene increases instead, while the competitiveness of polar ethanol decreases significantly.

Biochar for the Removal of Emerging Pollutants from Aquatic Systems: A Review

Water contaminated with emerging pollutants has become a serious environmental issue globally. Biochar is a porous and carbon-rich material produced from biomass pyrolysis and has the potential to be used as an integrated adsorptive material. Many studies have shown that biochar is capable to adsorb emerging pollutants from aquatic systems and could be used to solve the water pollution problem. Here, we provided a dual perspective on removing emerging pollutants from aquatic systems using biochar and analyzed the emerging pollutant removal efficiency from the aspects of biochar types, pollutant types and coexistence with heavy metals, as well as the associated mechanisms. The potential risks and future research directions of biochar utilization are also presented. This review aims to assist researchers interested in using biochar for emerging pollutants remediation in aquatic systems and facilitate research on emerging pollutants removal, thereby reducing their environmental risk.

Struvite crystallization by using active serpentine: An innovative application for the economical and efficient recovery of phosphorus from black water

Recovery of phosphorus from wastewater through struvite crystallization is one of the most attractive methods. However, the cost of chemical consumption makes this technology is unattractive to some extent. In this work, highly active serpentine was prepared by one-step mechanical activation and then used to recover phosphate as struvite from the black water containing 132.8 mg/L phosphorus and 3144 mg/L ammonia nitrogen. The results indicated that the prepared active serpentine can release magnesium ions and hydroxide ions simultaneously into an aqueous solution and is an ideal raw material for struvite crystallization. The factors for phosphorus recovery in this process mainly include mechanical activation intensity, serpentine dosage, and contact time. For the actual black water, a high recovery rate of phosphorus (>98%) is achieved by using active serpentine as the magnesium and alkali source for struvite precipitation. The recovery product was identified as struvite with a median particle size of 32.96 μm. It was confirmed that the mechanical activation damaged the crystal structure of the raw serpentine, improving the activity of Mg²⁺ and OH^-. The undissolved Si-containing particles act as crystal seeds, accelerating the struvite crystallization process. Furthermore, a pilot-scale test was conducted with a rural public toilet in Xiong'an New District, Hebei Province. The results showed that an acceptable phosphorus recovery (98%) could be achieved using active serpentine. Additionally, it was demonstrated that the serpentine process to recover phosphate as struvite reduced the cost by 54.4% in compared with an ordinary chemical process. The active serpentine is a promising dual source of magnesium and alkali for the phosphorus recovery by the struvite method. It has a potential prospect for the large-scale application in phosphorus recovery and struvite fertilizer production.

Sustainable Mitigation of Paracetamol with a Novel Dual-Functionalized Pullulan/Kaolin Hydrogel Nanocomposite from Simulated Wastewater

In the present investigation, a novel, green, and economical dual-functionalized pullulan/kaolin hydrogel nanocomposite (f-PKHN) was fabricated and subsequently applied for the liquid-phase decontamination of paracetamol (PCT), a pharmaceutical pollutant. Pullulan and kaolin were functionalized with l-asparagine and gallic acid, respectively. The physicochemical facets of the functionalized pullulan/kaolin hydrogel nanocomposite and its interactive behavior with PCT were elucidated by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDX), and elemental mapping. The process parameters along with the isotherm, kinetics, and thermodynamics were methodically appraised via a batch technique to unveil the adsorption performance of the as-fabricated hydrogel nanocomposite. The adsorption isotherm and kinetics of PCT uptake by f-PKHN conform well to Freundlich and pseudo-second-order models, respectively. Relying on hydrogen bonding, n-π, and van der Waals interactions, the maximum adsorption capacity was 332.54 mg g^-1, higher than for most of the previous adsorbents reported in the literature for PCT removal. Thermodynamic calculations corroborated endothermic, spontaneous, and feasible adsorption phenomena. The maintenance of a high uptake percentage (69.11%) in the fifth consecutive adsorption-desorption cycle implied the significant reusable potential of f-PKHN. Swelling studies exhibited 90% swelling within 200 min, indicating the successful fabrication of a cross-linked hydrogel network. The real water (distilled water, tap water, and river water) samples spiked with PCT specified a significant uptake of PCT (>85%), and the minor influence of ionic strength on the adsorptive potential of f-PKHN validated its potentiality for the decontamination of real effluents. In conclusion, f-PKHN with substantial adsorption capacity, green characteristics, and excellent reusability can be reckoned with as a promising adsorbent for the de-escalation of PCT from aquatic sources as well as at the industrial level.

Development of a novel and efficient biochar produced from pepper stem for effective ibuprofen removal

A potential biochar from pepper stems (PS-biochar) was developed via a one-stage pyrolysis process of precursor at 700 °C and employed to adsorb ibuprofen (IBP) in water media. Results showed that PS-biochar was a carbonaceous mesoporous adsorbent with well-developed porosity (S_BET = 727.5 m²/g and V_Total = 0.36 cm³/g) and rich surface functional groups. Mechanism of IBP adsorption consisted mainly of π- π interaction, pore filling, and H-bonding. The Langmuir monolayer capacity (569.6 mg/g) was very high compared to values reported in similar studies. The successful PS-biochar regeneration after four cycles in the batch system confirmed the high performance of the NaOH (0.1 M) as a desorbing agent. Therefore, the prepared biochar can be considered as a cost-effective and high-performance material for water decontamination.

Removal of diclofenac and oxytetracycline from synthetic urine by furfuryl alcohol-derived mesoporous carbon

In this study, using furfuryl alcohol as the precursor carbon and mesoporous silica as the template, and furfuryl alcohol-derived mesoporous carbon (FMC) was prepared. The specific surface area of FMC was 1022.61 m²/g, the pore volume was 1.71 cm³/g, and the mesoporous volume was 98.8%. Based on the adsorption kinetics of pharmaceuticals onto the FMC in synthetic urine, equilibrium adsorption was reached in 120 min, and it followed a pseudo-second-order model. The adsorption isotherms were well-fitted by the Sips isotherm model, and the saturated adsorption capacities of diclofenac and oxytetracycline in fresh urine were 411.8 mg/g and 465.9 mg/g, respectively. Batch experiment results showed that pharmaceutical removal was strongly influenced by urine components such as sodium chloride, urea, and ammonium hydroxide. The adsorption of diclofenac and oxytetracycline was influenced by many factors including π-π interactions, hydrogen bonds, and electrostatic forces. FMC exhibited excellent reusability and retained urine nutrients during pharmaceutical adsorption.

Nano-sized hematite-assembled carbon spheres for effectively adsorbing paracetamol in water: Important role of iron

This study developed a new α-Fe2O3 (hematite) nanoparticles-loaded spherical biochar (H-SB) through the direct pyrolysis of glucose-derived spherical hydrochar and FeCl3. The optimal impregnation ratio (hydrochar and FeCl3) was 1/1.25 (wt/wt). H-SB was applied to remove paracetamol (PRC) from water. Results indicated that H-SB exhibited a relatively low surface area (127 m2/g) and total pore volume (0.089 cm3/g). The presence of iron particles in its surface was confirmed by scanning electron microscopy with energy dispersive spectroscopy. The dominant form of iron nanoparticles (α-Fe2O3) in its surface was confirmed by X-ray powder diffraction and Raman spectrum. The crystallite size of α-Fe2O3 in H-SB was 27.4 nm. The saturation magnetization of H-SB was 6.729 cmu/g. The analysis of Fourier-transform infrared spectroscopy demonstrated that the C-O and O-H groups were mainly responsible for loading α-Fe2O3 nanoparticles in its surface. The adsorption study indicated the amount of PRC adsorbed by H-SB slightly decreased within solution pH from 2 to 11. The adsorption reached a fast saturation after 120 min. The Langmuir maximum adsorption capacity of H-SB was 49.9 mg/g at 25 °C and pH 7.0. Ion-dipole interaction and π-π interaction played an important role in adsorption mechanisms, while hydrogen bonding and pore filling were minor. Therefore, H-SB can serve as a promising material for treating PRC-contaminated water streams.

ELECTRONIC SUPPLEMENTARY MATERIAL

Supplementary material is available in the online version of this article at 10.1007/s11814-021-1013-z.

Potential application of machine learning for exploring adsorption mechanisms of pharmaceuticals onto biochars

The increasing accumulation of pharmaceuticals in aquatic ecosystems could impair freshwater quality and threaten human health. Despite the adsorption of pharmaceuticals on biochars is one of the most cost-effective and eco-friendly removal methods, the wide variation of experimental designs and research aims among previous studies pose significant challenge in selecting biochar for optimal removal. In this work, literature data of 1033 sets with 21 variables collected from 267 papers over ten years (2010-2020) covering 19 pharmaceuticals onto 88 biochars were assessed by different machine learning (ML) algorithms i.e., Linear regression model (LM), Feed-forward neural networks (NNET), Deep neutral networks (DNN), Cubist, K-nearest neighbor (KNN), and Random forest (RF), to predict equilibrium adsorption capacity (Q_e) and explore adsorption mechanisms. LM showed the best performance on ranking importance of input variables. Except for initial concentration of pharmaceuticals, Q_e was strongly governed by biochars' properties including specific surface area (BET), pore volume (PV), and pore structure (PS) rather than pharmaceuticals' properties and experimental conditions. The most accurate model for estimating Q_e was achieved by Cubist, followed by KNN, RF, KNN, NNET and LM. The generalization ability was observed by the tuned Cubist with 26 rules for the prediction of the unseen data. This study not only provides an insightful evidence for data-based adsorption mechanisms of pharmaceuticals on biochars, but also offers a potential method to accurately predict the biochar adsorption performance without conducting any experiments, which will be of high interests in practice in terms of water/wastewater treatment using biochars.

Novel insights into the adsorption of organic contaminants by biochar: A review

With rising concerns in the practical application of biochar for the remediation of environment influenced by various organic contaminants, a critical review to facilitate insights the crucial role that biochar has played in wastewater and polluted soil decontamination is urgently needed. This research therefore aimed to describe different intriguing dimensions of biochar interactions with organic contaminants, which including: (i) an introduction of biochar preparation and the related physicochemical properties, (ii) an overview of mechanisms and factors controlling the adsorption of organic contaminants onto biochar, and (iii) a summary of the challenges and an outlook of the further research needs in this issue. In the light of the survey consequences, the appearance of biochar indicates the potential in substituting the existing costly adsorbents, and it has been proved that biochar is one promising adsorbent for organic pollutants adsorption removal from water and soil. However, some research gaps, such as dynamic adsorption, potential environmental risks, interactions between biochar and soil microbes, novel modification techniques, need to be further investigated to facilitate its practical application. This research will be conductive to better understanding the adsorption removal of organic contaminants by biochar.

State of the art of urine treatment technologies: A critical review

Over the last 15 years, urine treatment technologies have developed from lab studies of a few pioneers to an interesting innovation, attracting attention from a growing number of process engineers. In this broad review, we present literature from more than a decade on biological, physical-chemical and electrochemical urine treatment processes. Like in the first review on urine treatment from 2006, we categorize the technologies according to the following objectives: stabilization, volume reduction, targeted N-recovery, targeted P-recovery, nutrient removal, sanitization, and handling of organic micropollutants. We add energy recovery as a new objective, because extensive work has been done on electrochemical energy harvesting, especially with bio-electrochemical systems. Our review reveals that biological processes are a good choice for urine stabilization. They have the advantage of little demand for chemicals and energy. Due to instabilities, however, they are not suited for bathroom applications and they cannot provide the desired volume reduction on their own. A number of physical-chemical treatment technologies are applicable at bathroom scale and can provide the necessary volume reduction, but only with a steady supply of chemicals and often with high demand for energy and maintenance. Electrochemical processes is a recent, but rapidly growing field, which could give rise to exciting technologies at bathroom scale, although energy production might only be interesting for niche applications. The review includes a qualitative assessment of all unit processes. A quantitative comparison of treatment performance was not the goal of the study and could anyway only be done for complete treatment trains. An important next step in urine technology research and development will be the combination of unit processes to set up and test robust treatment trains. We hope that the present review will help guide these efforts to accelerate the development towards a mature technology with pilot scale and eventually full-scale implementations.

Competitive adsorption of multicomponent volatile organic compounds on biochar

Crude oil contaminated lands are recognised to have significant contributions to airborne volatile organic compounds (VOCs) with adverse effects on human health and tropospheric ozone. Soil capping systems for controlling harmful emissions are critical engineering solutions where advanced soil remediation techniques are neither available nor feasible. Studies on the adsorption of single VOC species in biochar have shown promising results as a potential capping material; however, current understanding of mixed gas system and multi-component adsorption of VOCs on biochar which would represent more realistic in situ conditions is very limited. We present, for the first time, the results of a study on competitive adsorption of mixed VOCs, including aromatic and non-aromatic VOCs commonly emitted from crude oil contaminated sites on two types of biochar pyrolysed at 500°C from wheat straw and bagasse as feedstock. The kinetics of sorption of multicomponent VOCs including acetone, hexane, toluene and p-xylene in biochar are studied based on the results of an extensive experimental investigation using a bespoke laboratory setup. Both biochar types used in this study presented a high sorption capacity for VOC compounds when tested individually (51-110 mg/g). For the multicomponent mixture, the competition for occupying sorption sites on biochar surface resulted in a lower absolute sorption capacity for each species, however, the overall sorption capacity of biochar remained more or less similar to that observed in the single gas experiments (50-109 mg/g). The chemical interactions via hydrogen bonds, electrostatic attraction, and pore-filling were found to be the main mechanisms of adsorption of VOC in the biochar studied. The efficiency of biochar regeneration was assessed through five cycles of adsorption-desorption tests and was found to be between 88% and 96%. The incomplete desorption observed confirm the formation of likely permanent bonds and heel build-ups during the sorption process.

Removal of pharmaceuticals from nitrified urine

In this study, granular activated carbon (GAC) was examined for the removal of five of the most commonly detected pharmaceuticals (naproxen, carbamazepine, acetaminophen, ibuprofen and metronidazole) from a nitrified urine to make the urine-derived fertiliser nutrient safe for food crops. Batch experiments were conducted to investigate the adsorption kinetics that described the removal of micropollutants (equal concentrations of 0.2 mM) from the synthetic nitrified urine at different GAC dosages (10-3000 mg/L). Artificial neural network modelling was also used to predict and simulate the removal of pharmaceuticals from nitrified urine. Langmuir and Freundlich isotherm models described the equilibrium data, with the Langmuir model providing slightly higher correlations. At the highest dose of 3000 mg/L GAC, all the pharmaceuticals showed a removal rates of over 90% after 1 h of adsorption time and 99% removal rates after 6 h of adsorption time. This study concludes that GAC is able to remove the targeted xenobiotics without affecting the concentration of N and P in the urine, suggesting that nitrified urine could be safely used as a nutrient product in future.

Synergistic adsorption and degradation of sulfamethoxazole from synthetic urine by hickory-sawdust-derived biochar: The critical role of the aromatic structure

This study investigated the adsorptive removal and subsequent degradation of sulfamethoxazole (SMX) from a synthetic urine by biochar (BC). The BCs used in this study were prepared using two different feedstocks with different temperatures. Element analysis and Fourier transform infrared spectroscopy (FTIR) results suggested that the aromaticity of one of the BCs, 700HSBC was significantly different from the 700PSBC although both of them were prepared at the same temperature (700 °C) with similar pore size distributions and specific surface areas. Due to the presence of abundant aromatic structures, 700HSBC showed a higher SMX uptake than 700PSBC, suggesting that the π-π interaction was the main adsorption mechanism. The removal of SMX from the urine was significantly enhanced by adding hydrogen peroxide to the 700HSBC. The carbonate radicals degradation of SMX mechanism was proposed and verified. With 700HSBC having abundant aromatic structures acting as π-electron donors, it could be an efficient activator for peroxymonocarbonate (HCO₄^-) to generate carbonate radicals. Hence, it could be concluded that the aromatic structures on BCs play a key role in both of the adsorption and hydrogen peroxide degradation of the SMX resulting in its removal from urine.

Characterization Techniques as Supporting Tools for the Interpretation of Biochar Adsorption Efficiency in Water Treatment: A Critical Review

Over the past decade, biochar (BC) has received significant attention in many environmental applications, including water purification, since it is available as a low-cost by-product of the energetic valorisation of biomass. Biochar has many intrinsic characteristics, including its porous structure, which is similar to that of activated carbon (AC), which is the most widely used sorbent in water treatment. The physicochemical and performance characteristics of BCs are usually non-homogenously investigated, with several studies only evaluating limited parameters, depending on the individual perspective of the author. Within this review, we have taken an innovative approach to critically survey the methodologies that are generally used to characterize BCs and ACs to propose a comprehensive and ready-to-use database of protocols. Discussion about the parameters of chars that are usually correlated with adsorption performance in water purification is proposed, and we will also consider the physicochemical properties of pollutants (i.e., K_ow). Uniquely, an adsorption efficiency index BC/AC is presented and discussed, which is accompanied by an economic perspective. According to our survey, non-homogeneous characterization approaches limit the understanding of the correlations between the pollutants to be removed and the physicochemical features of BCs. Moreover, the investigations of BC as an adsorption medium necessitate dedicated parallel studies to compare BC characteristics and performances with those of ACs.

Activated Carbon for Pharmaceutical Removal at Point-of-Entry

Pharmaceuticals are an increasing problem in waterways due to improper disposal and lack of removal at wastewater treatment plants. Long-term exposure impacts to humans are unknown but have been observed in model organisms (i.e., fish), impacting reproduction, changing temperament, and causing organ damage. The application of activated carbon (AC) for organic contaminant removal is widespread and applied successfully for water treatment. The objective of this study is to rapidly adsorb ibuprofen using AC to determine the feasibility as a point-of-entry treatment option for removal of pharmaceuticals in the toilet. AC factors analyzed include type of AC raw material, adsorbent particle size, contact time, and competitive adsorption of ibuprofen and common toilet bowl cleaner components such as chlorine and methylene blue dye. A coconut-based AC with a high surface area adsorbed the highest quantity of ibuprofen. There was no significant impact to ibuprofen adsorption upon the introduction of other compounds to the solution, thus demonstrating rapid adsorption and the potential for application at the point-of-entry.

Sorption behaviour of xylene isomers on biochar from a range of feedstock

Inland oil spillage is one of the widespread sources of crude oil volatile organic compound emissions (CVEs) for which the long-term remedial solutions are often complex and expensive. This paper investigates the potential of a low-cost containment solution for contaminated solids by volatile organic compounds (VOCs) using biochar. The results of an extensive experimental investigation are presented on the sorption kinetics of xylene isomers (one type of the most frequently detected CVEs) on commercial biochar produced by prevalent feedstocks (wheat, corn, rice and rape straw as well as hardwood) at affordable temperatures (300-500°C). Chemical and physical properties of biochar were analysed in terms of elemental composition, scanning electron microscopy, specific surface area, ATR-FTIR spectra and Raman spectrometry. We show that for high-temperature biochar with similar surface chemistry, the sorption efficiency is mainly controlled by porous structure and pore size distribution. Biochar samples with higher specific surface area and higher volume of mesopores showed the highest sorption capacity (45.37-50.88 mg/g) since the sorbate molecules have more access to active sites under a greater intra-particle diffusion and elevated pore-filling. P-xylene showed a slightly higher sorption affinity to biochar compared to other isomers, especially in mesoporous biochar, which can be related to its lower kinetic diameter and simpler molecular shape. The sorption capacity of biochar produced at higher pyrolysis temperatures was found to be more sensitive to changes in ambient temperature due to dominant physical adsorption. Elovich kinetic model was found to be the best model to describe xylenes' sorption on biochar which indirectly indicates π-π stacking and hydrogen bonding as the main mechanism of xylene sorption on these types of biochar.

Innovative spherical biochar for pharmaceutical removal from water: Insight into adsorption mechanism

In this study, we developed an innovative spherical biochar with high porosity and excellent paracetamol (PRC) adsorption capacity. The optimal pyrolysis temperatures for the preparation of spherical biochar (derived from pure glucose) and non-spherical biochar (from pomelo peel wastes) were obtained at 900 °C and 700 °C, respectively. Various advanced techniques were applied to characterize the prepared biochars. Spherical and non-spherical biochars exhibited large specific surface area (1292 and 1033 m²/g) and high total pore volume (0.704 and 1.074 cm³/g), respectively. The adsorption behavior of PRC onto two biochars was conducted utilizing batch experiments. Results demonstrated that the adsorption process was slightly affected by the change of solution pH (2-11) and addition of NaCl (0.05-1.0 M) and was able to achieve fast equilibrium (∼120 min). The maximum adsorption capacity of spherical biochar (286 mg/g) for PRC was approximately double that of non-spherical biochar (147 mg/g). The signal of thermodynamic parameters was negative ΔG° and ΔH° values, but positive ΔS° value. The adsorption mechanism consisted of pore-filling, hydrogen bonding formations, n-π and π-π interactions, and van der Waals force. The adsorption capacities of two biochars were insignificantly dependent on different real water samples containing PRC. Consequently, the biochars can serve as a green and promising material for efficiently removing PRC from water.

Removal of doxorubicin by magnetic copper phosphate nanoflowers for individual urine source separation

Doxorubicin (DOX) originated from users' urine has been an emerging environmental pollutant due to its significant genotoxicity to mankind. Thus, urine source separation is a potential strategy to isolate DOX at a higher concentration and reduce the burden of downstream wastewater treatment. To develop highly efficient, easy separation and retrievable materials for individual patient to conveniently remove DOX from own urine, magnetic Cu₃(PO₄)₂ nanoflowers were prepared through anchoring amino-functionalized magnetic nanoparticles on the Cu₃(PO₄)₂ nanoflowers. Characterizations revealed the magnetic nanoflowers were spherical in shape with a mean size of 15 μm, and porous and hierarchical in structure. Magnetic nanoparticles located the surface of petals. Multibatch experiments were performed to assess the removal performance of DOX from aqueous solution. The magnetic nanoflowers exhibited excellent removal efficiency of DOX under weakly alkaline condition at ambient temperature. Linear and non-linear analyses were carried out to compare the best fitting kinetics and isotherms. Sorption kinetic data best fitted the pseudo-second order model. The Freundlich isotherm explained equilibrium sorption data with R² = 0.993 higher than that for the Langmuir isotherm. When the pH of synthetic urine was adjusted to weakly alkaline (pH 8.0-9.0), over 95% of DOX (20 mg L^-1) was removed by a little of magnetic nanoflowers (50 mg L^-1) within 5 min. Meanwhile, the magnetic nanoflowers could be easily separated and recovered from the synthetic urine by a magnet. So, for individual urine source separation strategy, the magnetic nanoflower seems to be an efficient, convenient and inexpensive approach to remove DOX from human urine.

Removal of phosphate from aqueous solution using MgO-modified magnetic biochar derived from anaerobic digestion residue

A novel MgO-modified magnetic biochar (MgO@MBC) was made by chemical co-precipitation of Mg²⁺/Fe³⁺ on anaerobic digestion residue (ADR) and subsequently pyrolyzing at different temperatures. MgO@MBC was used for phosphate recovery from aqueous solution. The physicochemical properties of MgO@MBC were comprehensively investigated using TEM-EDS, FT-IR, XRD, VSM, N₂ adsorption-desorption and TGA. Results showed that MgO/γ-Fe₂O₃ nanoparticles were successfully deposited onto the surface of BC. The effects of reaction temperature, initial solution pH, MgO@MBC dosage, coexisting anions and phosphate concentration on the removal of phosphate by MgO@MBC were researched. Additionally, the adsorption process of phosphate onto MgO@MBC was well described by the pseudo second-order and pseudo first-order models, which indicated a chemisorption and physisorption process. Besides, the maximum adsorption capacity of MgO@MBC for phosphate by the Langmuir model were 149.25 mg/g at 25 °C. Moreover, the thermodynamic study suggested that the adsorption of phosphate onto MgO@MBC was a spontaneous and endothermic process. The adsorption mechanisms including physical absorption, surface electrostatic attraction, surface complexation and precipitation were revealed. It could be concluded that MgO@MBC exhibited high removal efficiency of phosphate and excellent magnetic property for the recovery. MgO@MBC could be utilized as a magnetically recoverable adsorbent to realize phosphate recovery and MgO@MBC after the adsorpion of phosphate could be applied in agricultural production as a fertilizer.

Opportunities for Building-Scale Urine Diversion and Challenges for Implementation

Urine diversion (i.e., urine source separation) has been proposed as a more sustainable solution for water conversation, nutrient removal and recovery, and pharmaceutical sequestration. As wastewater regulations become more stringent, wastewater treatment plants reach capacity, and water resources become more strained, the benefits of urine diversion become more appealing. By using nonwater urinals and urine-diverting toilets, urine diversion systems seek to collect undiluted human urine for nutrient recovery and pharmaceutical sequestration. Urine is a unique, nutrient-rich waste stream that constitutes an overall low volume of waste entering a wastewater treatment plant. If urine is separated at the building-scale, various technologies can be used to recover nutrients and sequester pharmaceuticals at their most concentrated location. However, the implementation of urine diversion requires a paradigm shift from conventional comingling of wastewater and centralized treatment to source separation and decentralized treatment. This Account proposes a vision for building-scale implementation of urine diversion with the goal of clarifying the opportunities and challenges in this context. The main components of urine, i.e., nitrogen, phosphorus, potassium, and pharmaceuticals, are major drivers for technology development and system implementation. Stepping back, the benefits from water conservation and effects on wastewater treatment are an extension of the system boundary that can impact the sustainability of adjacent systems. However, major challenges have been identified in the literature as hurdles for widespread implementation of urine diversion. Challenges include the comparison of recovering nutrients at the wastewater plant versus at the source, the collection and storage of urine, the ability to recover nutrients and sequester pharmaceuticals, and the overall environmental and economic impacts of urine diversion systems. While these challenges exist, studies have been conducted to address some of the underlying research questions. As more research is conducted, the vision of a seamless urine diversion system with building-wide plumbing and storage comes closer to reality. As such, the application of urine diversion systems will benefit from technology development and research to fill gaps that have been identified. It is important to classify urine diversion systems as a process and not a product. This has implications for the way these systems are evaluated, as their impact on peripheral systems can be of benefit to different stakeholders. In the same light, new research areas, such as cyber-physical systems, reverse logistics, and sustainability transitions, can be applied to urine diversion as approaches for ensuring a robust process for widespread implementation. However, established technologies should be constantly reassessed and enhanced by newer techniques. For example, membrane distillation, eutectic freeze concentration, and solar evaporation should be considered for nutrient recovery and volume reduction because they offer benefits over conventional technologies. Finally, the human behavior component of urine diversion cannot be ignored, as negative user acceptance and improper maintenance of these systems can have a detrimental impact on their future implementation.