Adsorption Of NH4 Research Articles

Simultaneous adsorption of ammonia nitrogen and phosphate on electro-assisted magnesium/aluminum-loaded sludge-based biochar and its utilization as a plant fertilizer.

Herein, Mg/Al-loaded sludge-based biochar was prepared via electro-assisted impregnation. The structure and chemical analysis of modified sludge-based biochar (MgSBC-0.5(@Al) showed that the material was loaded with MgO and Al2O3. The specific surface area of MgSBC-0.5(@Al) was 11.27 times higher than that of unmodified sludge-based biochar (SBC). The simultaneous adsorption performance of MgSBC-0.5(@Al for ammonia nitrogen (NH4+-N) and phosphate phosphorus (PO43--P) was studied. The maximum adsorption capacities of MgSBC-0.5(@Al for NH4+-N and PO43--P at 298 K were 65.19 and 92.10 mg·g-1, respectively, 4.45 and 6.28 times higher than those of SBC. The external and internal elemental compositions of the modified and unmodified biochar specimens were quantitatively characterized using inductively coupled plasma mass spectrometry, X-ray photoelectron spectroscopy, and X-ray fluorescence spectrometry. The results emphasized the importance of Mg-loading for NH4+-N and PO43--P capture. MgO was mainly loaded on the surface of biochar, enabling adsorption through chemical reactions. Analysis showed that the adsorption of NH4+-N and PO43--P on the modified biochar proceeded simultaneously through multiple mechanisms. Particularly, the adsorption of NH4+-N and PO43--P occurred through the precipitation of struvite and physical adsorption, with PO43--P also adsorbed through the formation of MgHPO4 and CaHPO4. Other data indicated that Al, Ca, and Fe had a trapping effect on the adsorbate. Importantly, the biochar after adsorption could be used as a soil amendment.

Mechanism of ammonium adsorption onto the surface of heteroatom doped graphene quantum dots

The adsorption mechanism of ammonium (NH4+) ion onto graphene quantum dots (GQDs) surface, modified with vacancy and heteroatom (nitrogen (N) and oxygen (O)), has been studied using a combination of dispersion-corrected density functional theory (DFT) and quantum theory of atoms in molecules (QTAIM) approaches in aqueous media. The potential of GQD-NX and GQD-OX surfaces as highly effective adsorbents for NH4+ ions has been explored by detailed analysis of adsorption energies, molecular electrostatic potential, charge transfer, density-of-states, non-covalent interaction, and desorption time. It has been observed that the adsorption of NH4+ ions on the GQD-NX surfaces is primarily chemisorption, governed by electrostatic interactions and hydrogen bonds. However, adsorption of NH4+ over the surface of GQD-OX predominantly ranges from strong physisorption to weak chemisorption arising from van der Waals interactions and hydrogen bonds. These findings present compelling new approach utilizing modified GQDs as highly efficient adsorbents for removing NH4+ ions from water.

Copper supported Dowex50WX8 resin utilized for the elimination of ammonia and its sustainable application for the degradation of dyes in wastewater

To obtain high efficient elimination of ammonia (NH4+) from wastewater, Cu(II), Ni(II), and Co(II)) were loaded on Dowex-50WX8 resin (D-H) and studied their removal efficiency towards NH4+ from aqueous solutions. The adsorption capacity of Cu(II)-loaded on D-H (D-Cu2+) towards NH4+ (qe = 95.58 mg/g) was the highest one compared with that of D-Ni2+ (qe = 57.29 mg/g) and D-Co2+ (qe = 43.43 mg/g). Detailed studies focused on the removal of NH4+ utilizing D-Cu2+ were accomplished under various experimental conditions. The pseudo-second-order kinetic model fitted well the adsorption data of NH4+ on D-Cu2+. The non-linear Langmuir model was the best model for the adsorption process, producing a maximum equilibrium adsorption capacity (qmax = 280.9 mg/g) at pH = 8.4, and 303 K in less than 20 min. The adsorption of NH4+ onto D-Cu2+ was an exothermic and spontaneous process. In a sustainable step, the resulting D-Cu(II)-ammine composite from the NH4+ adsorption process displayed excellent catalytic activity for the degradation of aniline blue (AB) and methyl violet 2B (MV 2B) dyes utilizing H2O2 as an eco-friendly oxidant.

Efficient removal of ammonia nitrogen using biochar derived from the co-fermentation residue of waste activated and orange peel waste: Linking structure properties and reaction kinetics

Elevating ammonia nitrogen (NH4+-N) levels pose substantial threats to both human health and ecological systems. Employing adsorption as a strategic approach for NH4+-N removal is appealing due to its operational simplicity and high efficiency. Prior studies have successfully harnessed valuable volatile fatty acids through the anaerobic co-fermentation of waste activated sludge (WAS) and orange peel waste (OPW). Nevertheless, the proper disposal of the resulting fermentation residue remains a critical concern. This study highlights the effectiveness of biochar derived from WAS/OPW co-fermentation residue in adsorbing NH4+-N in aquatic environments. The highest NH4+-N removal rates were attained at 9.76, 44.1, 76.0, and 97.8 % for biochar dosages of 3, 5, 8, and 10 g/L, respectively. The adsorption of NH4+-N by biochar closely aligns with the Langmuir model and exhibits compatibility with both pseudo-first and pseudo-second kinetic models. This implies a single-layer adsorption process with the simultaneous occurrence of physical and chemical adsorption. Subsequent analysis revealed that, relative to fermentation residue, biochar exhibited a more porous structure post-pyrolysis, with a specific surface area 3.43 times larger, increased pore volume, and additional mesopores. Furthermore, the biochar displayed a higher abundance of functional groups and metal oxides after pyrolysis, collectively contributing to its robust adsorption capability for NH4+-N. This research introduces a promising approach for mitigating NH4+-N pollution in aquatic environments while concurrently enhancing the resource utilization of organic solid waste.

Adsorption behavior of NH4+ and Mg2+ at kaolinite surfaces: Effect of the ion concentration, NH4+/Mg2+ mixing ratio, and layer charge

AbstractThe adsorption behavior of NH4+ and Mg2+ at kaolinite surfaces was investigated by using molecular dynamics (MD) simulations, considering the factors such as ion concentration, NH4+/Mg2+ mixing ratio, and layer charge of kaolinite. The results showed that the increase in ion concentration did not affect the adsorption modes of NH4+ and Mg2+ ions but promote the increase in the adsorption capacity. The total adsorption capacities of Mg2+ and NH4+ were 3.25 × 10−6 and 2.85 × 10−6 μmol·mm−2 at the ion concentration of 1.5 mol·L−1, respectively. When NH4+ and Mg2+ were co‐adsorbed, they could inhibit the adsorption of each other at the surface of kaolinite, except that the inner‐sphere (IS) adsorption of NH4+ at aluminum hydroxyl (Al–OH) surface could be enhanced by the presence of Mg2+. Both NH4+ and Mg2+ tended to adsorb at the siloxane (Si–O) surface of kaolinite rather than Al–OH surface. When layer charge occurred in kaolinite, a small number of Mg2+ began to adsorb in the IS complexes at 1.7 and 2.3 Å above the Al and O atoms of the lattice‐substituted tetrahedra of the Si–O surface, and at 1.7 Å above the hexahedra of the Al–OH surface. However, most of NH4+ were adsorbed in IS complexes at 1.7 Å above the center of the oxygen six‐membered ring of the Si–O surface and above the hexahedron of the Al–OH surface. The adsorption capacity of Mg2+ changed little with the increase of layer charge density, while the IS and total adsorption capacity of NH4+ increased significantly.

Karst rocky desertification restoration increases soil inorganic N supply to reduce plant N limitation

Nitrogen (N) limitation of plant growth following vegetation restoration is widespread in global terrestrial ecosystems, especially in karst rocky desertification areas. However, neither the temporal changes in plant N limitation during the restoration of those areas nor the mechanisms underlying N availability are well understood. In this study, several indicators reflecting soil N availability, N transformation rates, and plant communities were investigated in four areas in southwest China differing in their grade of rocky desertification. Our results showed that plant growth was severely N limited in the intense rocky desertification areas. The plant community-level foliar N content, 15N values, and N:P ratio increased significantly as the rocky desertification grade decreased, indicating a decrease in plant N limitation. This was attributed to increased soil N availability, evidenced by the higher soil δ15N values as well as total N and inorganic N contents along the rocky desertification grade. With the decreasing rocky desertification grade, the rates of organic N conversion to ammonium (NH4+) and nitrate (NO3–), the adsorption of NH4+ on cation-exchange sites, and the release of adsorbed NH4+ increased significantly, which could enhance soil inorganic N supply capacity and accelerate NH4+ turnover to increase N availability. Noticeably, the sharp decrease in the rate of NH4+ oxidation to NO3– with the decrease in the rocky desertification grade led to a shift in inorganic N from NO3–-dominated to NH4+-dominated. The increased contents of soil organic matter, calcium, iron-aluminum oxides, and sand, the proportion of aggregates > 2 mm, as well as the greater abundances of fungi and bacteria were the primary drivers of the N transformation rates along the rocky desertification grade. Overall, our study highlights the importance of N cycling in controlling N availability and thus in determining plant N limitation in karst rocky desertification areas. The results of the study provide a scientific basis for the ecological restoration of rocky desertification in karst ecosystems.

Co-hydrothermal carbonization of rape straw and industrial sewage sludge – Applications of hydrochar for N and P adsorptions and for agricultural/horticultural purposes

Reuse of agricultural and industrial wastes simultaneously to prepare hydrochars (HCs) for removal of NH4+ and PO43− in practical sewage without additional wastes produced is still a challenge. Herein, HCs were fabricated by combination of rape straw and industrial sewage sludge to remove NH4+ and PO43− from hoggery effluent. Synthesis conditions were firstly optimized and optimized HC (OPT-HC) was further applied to adsorb NH4+ and PO43−. Monolayer and Pseudo-first-order as well as Pseudo-second-orders were confirmed via adsorption kinetic and isothermal adsorption studies. Morphologies and surface areas of the OPT-HC did not show any transformations before and after adsorption of NH4+ and PO43−. The OPT-HC after adsorption of NH4+ and PO43− (OPT–HC–N/P) was further applied as fertilizer for planting Ping-pong Chrysanthemum. Results indicate that the OPT–HC–N/P can improve comprehensive qualities of the Ping-pong Chrysanthemum such as plant height, fresh, Vitamin C, Chlorophyll, soluble protein and sugar because the OPT–HC–N/P can provide extra N and P elements and also promote to release available K in soil. OPT–HC–N/P treated Ping-pong Chrysanthemum open flowers in advance. Thus, two kinds of wastes were re-utilized to remove N and P in real-life effluent.

Adsorption of ammonium ion (NH4+) using mordenite-chitosan from synthetic and actual sewage: Batch and fixed-bed studies

The untapped NH4+ in sewage has the potential to be recovered as fertilizer via the adsorption process. While zeolite-chitosan has demonstrated better performance in nutrient recovery compared to powder zeolite, research on mordenite-chitosan remains limited. Therefore, this study focused on the mordenite-chitosan for NH4+ recovery. Based on the characterization, the physicochemical properties of mordenite-chitosan closely resemble the mordenite. The addition of chitosan has increased the adsorption capacity of mordenite by 15%. The adsorption of NH4+ on mordenite-chitosan fitted well to the Langmuir linear model with an estimated adsorption capacity of 17.7 mg/g (R2 = 0.991). The positive entropy with an enthalpy value of 44.47 kJ/mol suggests a random organization of NH4+ ions, endothermic process, and ion-exchange. Mordenite-chitosan adhered well to the Thomas model, with NH4+ adsorption capacity of 17.97 mg/g, 6.14 mg/g, and 4.84 mg/g in synthetic sewage, influent, and effluent, respectively. Factors such as the negativity of the surface mordenite-chitosan, Si/Al ratio, and framework flexibility are likely to influence the NH4+ adsorption capacity. Overall, the ion-exchange property of mordenite-chitosan emerges as the main contributor to its efficacy in NH4+ recovery.

Study of simultaneous adsorption of ammonium and phosphate in waters by La-F4A zeolites prepared from spent FCC catalyst

The problem of resource disposal of massive spent fluid catalytic catalyst needs to be solved urgently. Thus an environmentally friendly, highly efficient and economical cost adsorbent used for nitrogen and phosphorus removal was prepared from spent fluid catalytic catalyst. A novel 4A zeolite adsorbent loaded with lanthanum hydroxide (La-F4A) was prepared by acid leaching pretreatment, alkali fusion roasting hydrothermal and co-precipitation method. And use La-F4A in the study of simultaneous adsorption of ammonia-nitrogen and phosphorus in water. Adsorption experiments were carried out under the condition that the primordial concentrations of PO4 and NH4+-N were respectively 1 & 10mg/L. La-F4A has an adaptive adsorption ability on NH4+-N and PO4 in the pH range of 4-9. When the temperature is 298K, the dosage is 1.0 g/L, the contact time is 240 min, and test water pH=7, the maximum adsorption capacities for NH4+-N and PO4 are 7.64 mg/g and 0.93 mg/g respectively. The behaviours accord with the pseudo-second-order adsorption kinetic model. The adsorption of PO4 conforms to the Langmuir isotherm model while NH4+-N conforms to the Freundlich isotherm model. Coexisting anions have almost no effect on the adsorption of PO4, coexisting cations have different inhibitory effects on the adsorption of NH4+-N. After four desorption cycles, the removal efficiency of La-F4A for NH4+-N and PO4 was 77% and 93% of the initial capacity. There are both chemical adsorption and physical adsorption in the process. The ammonium removal mechanism is the ion exchange between NH4+ and Na+ in the framework, and the phosphate removal mechanism is the ligand exchange between PO4 and hydroxyl to form LaPO4. La-F4A is regarded to be an excellent adsorbent for ammonium and phosphate removal.

Purification effects of recycled aggregates from construction waste as constructed wetland filler

Three groups of constructed wetlands based on gravel (#1), asphalt concrete + red brick (#2), and red brick (#3) were constructed to explore their purification effects and the characteristics of microbial community structure. The results show that the construction waste recycled aggregates have little leaching risk of heavy metals; the adsorption of nitrogen and phosphorus by the three fillers could be well fitted by pseudo-first-order and pseudo-second-order kinetic models (R2 > 0.96); the adsorption of NH4+-N by the three fillers could be well fitted by the Freundlich model (R2 > 0.656); the adsorption of phosphorus could be well fitted by the Langmuir and Freundlich models, except for gravel (R2 > 0.875). The average removal rate of COD, NH4+-N, TN, and TP was 60.85 %, 94.69 %, 73.42 %, 39.12 % (#1); 67.32 %, 20.31 %, 22.26 %, 27.81 % (#2); 67.35 %, 17.7 %, 25.8 % and 46.98 % (#3). There was no significant difference in the purification effect of the three fillers on COD. The adsorption effect on NH4+-N was: gravel > red brick/asphalt concrete, and the adsorption effect on TP was: asphalt concrete > red brick > gravel. The microbial population richness of the upper filler was #2 > #1 > #3, the uniformity was #1 > #2 > #3, and the diversity was #1/#2 > #3. The microbial communities were dominated by Proteobacteria, Actinobacteriota, Bacteroidota and Chloroflexi.

Application of 15N tracing and bioinformatics for estimating microbial-mediated nitrogen cycle processes in oil-contaminated soils

Crude oil pollution can profoundly alter the nitrogen (N) cycle in the soil. Here, a 30-day incubation with 15N tracer approach was performed to assess the impacts of crude oil concentrations (medium: 10,000 mg kg−1; heavy: 50,000 mg kg−1) on soil N cycling based on a numerical model. Results showed that crude oil pollution significantly increased the gross N-transformation rates, but the rates of oxidation of recalcitrant organic N, the immbolization of NO3− and the adsorption of NH4+ changed differently as a function of hydrocarbon concentrations. There was no significant difference of the oxidation rate of recalcitrant organic N between the medium and heavy oil-contaminated soils (medium: 0.1149 mmol N kg−1 d−1; heavy: 0.1299 mmol N kg−1 d−1), but the rates of NO3− immobilization (0.1135 mmol N kg−1 d−1) and NH4+ adsorption were the highest (0.1148 mmol N kg−1 d−1) in the moderately oil-contaminated soils than those in the heavy polluted soil (0.0849 mmol N kg−1 d−1 and 0.0034 mmol N kg−1 d−1, respectively). The NO3− immobilization rate was 2.5-fold higher than its reduction rate, indicating that NO3− immobilization played a more important role during the process of NO3− transformation. Microbial community structure analysis indicated that phyla of Actinobacteria and Ascomycota respectively promoted the immobilization of NO3− to recalcitrant organic N and the reduction of NO3− to NH4+. The genus of Aspergillus was related to net NH4+ production, and the genera of Penicillium and Acremonium were responsible for oxidation of recalcitrant organic N to NO3−.

Grafting of R4N+-Bearing Organosilane on Kaolinite, Montmorillonite, and Zeolite for Simultaneous Adsorption of Ammonium and Nitrate.

Modification of aluminosilicate minerals using a R4N+-bearing organic modifier, through the formation of covalent bonds, is an applicable way to eliminate the modifier release and to maintain the ability to remove cationic pollutants. In this study, trimethyl [3-(trimethoxysilyl) propyl] ammonium chloride (TM) and/or dimethyl octadecyl [3-(trimethoxysilyl) propyl] ammonium chloride (DMO) were used to graft three aluminosilicate minerals, including calcined kaolinite (Kaol), montmorillonite (Mt), and zeolite (Zeol), and the obtained composites were deployed to assess their performance in regard to ammonium (NH4+) and nitrate (NO3−) adsorption. Grafting of TM and/or DMO had little influence on the crystal structures of Kaol and Zeol, but it increased the interlayer distance of Mt due to the intercalation. Compared to Kaol and Zeol, Mt had a substantially greater grafting concentration of organosilane. For Mt, the highest amount of loaded organosilane was observed when TM and DMO were used simultaneously, whereas for Kaol and Zeol, this occurred when only DMO was employed. 29Si-NMR spectra revealed that TM and/or DMO were covalently bonded on Mt. As opposed to NO3−, the amount of adsorbed NH4+ was reduced after TM and/or DMO grafting while having little effect on the adsorption rate. For the grafted Kaol and Zeol, the adsorption of NH4+ and NO3− was non-interfering. This is different from the grafted Mt where NH4+ uptake was aided by the presence of NO3−. The higher concentration of DMO accounted for the larger NO3− uptake, which was accompanied by improved affinity. The results provide a reference for grafting aluminosilicate minerals and designing efficient adsorbents for the co-adsorption of NH4+ and NO3−.

A novel chitosan modified magnesium impregnated corn straw biochar for ammonium and phosphate removal from simulated livestock wastewater

Livestock wastewater is an important source of agricultural non-point pollution, causes serious pollution to water bodies. At the same time, corn straw is also an important agricultural waste, and its resource utilization has been the focus of global attention. The novel biochar material made from corn stalk can be used to treat livestock wastewater, which is helpful to control agricultural non-point source pollution and improve the efficiency of agricultural waste resource utilization. A novel chitosan modified magnesium impregnated corn straw biochar (CS-MgCBC) was synthetic for the removal of NH4+-N and PO43−-P from livestock wastewater. The experiments results show that the adsorption of NH4+-N and PO43−-P by CS-MgCBC is more consistent with the second-order kinetic model and Langmuir model, and the maximum Langmuir adsorption capacity for NH4+-N (35.59 mg/g) and PO43−-P (221.89 mg/g), compared with other studies on NH4+-N and PO43−-P adsorption, the average maximum adsorption capacity of CS-MgCBC has been improved 48.3% and 68.9%. When pH = 6 and pH = 9, the adsorption effect of PO43−-P and NH4+-N can be reached 99.6% and 48.4%, respectively. The chitosan modification increased the surface area, and abundance of functional groups (-OH, -CH3, -NH2, etc.) on the surface of biochar, thus improving the adsorption capacity of CS-MgCBC. The electrostatic adsorption, precipitation, and ligands exchange were the main mechanisms in the sorption of NH4+-N and PO43−-P on CS-MgCBC. Excellent adsorption capacity and environmental-friendliness made CS-MgCBC an efficient adsorbent for the removal of NH4+-N and PO43−-P in livestock wastewater.

Analysis of the simultaneous adsorption mechanism of ammonium and phosphate on magnesium-modified biochar and the slow release effect of fertiliser

To decrease the eutrophication caused by nitrogen (N) and phosphorus (P) in water, magnesium-modified corn stalk biochar (MgB) was prepared under the synergistic impact of the multi-pyrolysis temperatures and Mg2+ contents for the co-adsorption of ammonium (NH4+-N) and phosphate (PO43−). The co-adsorption mechanism, slow-release performance and plant application of MgB were systematically studied. The results showed that pyrolysis temperatures (350–650 °C) and Mg2+(0–3.6 g/L) contents not only altered the physicochemical properties of biochar, but also significantly affected the adsorption efficacy of MgB. The adsorption of NH4+-N and PO43− was in accordance with Langmuir–Freundlich and pseudo-second-order kinetic models (Qmax = 37.72 and 73.29 mg/g, respectively). Based on the characteristics, adsorption kinetics and isotherms results, the adsorption mechanism was determined and found to mainly involve struvite precipitation, ion exchange, and surface precipitation or electrostatic attraction. Compared with the leaching performance of chemical fertilizers (CF), after adsorption of NH4+-N and PO43− (MgB-A), MgB had a more stable pH and lower conductivity. Leaching of NH4+-N and PO43− by MgB-A was controlled by both the diffusion mechanism and the dissolution rate of struvite and Mg-P. The excellent long-term slow-release performance and abundant Mg2+ of MgB-A promoted the growth of Zea mays L. and Lolium perenne L. Overall, this study suggested that MgB could realize a win–win outcome of struvite biochar-based fertiliser production and wastewater treatment.

Enhanced Nutrient Removal in A2N Effluent by Reclaimed Biochar Adsorption.

The excessive nitrogen and phosphorus discharged into the water environment will cause water eutrophication and thus disrupt the water ecosystem and even exert biological toxicities. In this study, the absorption removal of nitrogen and phosphorus from the anaerobic tank in an anaerobic–anoxic/nitrifying system using four different kinds of biowaste-reclaimed biochars were investigated and compared. The effects of temperature and pH on nutrient adsorption removal were further investigated. The four kinds of biochar were successfully prepared and well characterized using a scanning electron microscope, fourier transform infrared spectroscopy, X-ray diffraction and Brunner−Emmet−Teller methods. Generally, there was no significant change in chemical oxygen demand (COD) and NH4+-N removal efficiencies when treated by the different biochars, while the activated sludge biochar (ASB) displayed the highest total phosphorus (TP) removal efficiency. The initial TP concentrations (<40 mg/L) displayed no remarkable effects on the TP adsorption removal, while the increase of temperature generally enhanced TP and NH4+-N adsorptions on the ASB. Besides, the increase of pH significantly promoted NH4+-N removal but depressed TP removal. Moreover, the adsorption process of TP by the ASB complies with the secondary kinetic model, suggesting the chemical precipitation and physical electrostatic interaction mechanisms of TP adsorption removal. However, the adsorption of NH4+-N conformed to the inner-particle diffusion model, indicating that the NH4+-N adsorption was mainly involved with pore diffusions in the particles.

A facile technique to prepare MgO-biochar nanocomposites for cationic and anionic nutrient removal

The removal of NH4+ and PO43− from water using adsorbents produced from rice husk and corn cob byproducts was examined. The synthesis of MgO-biochar nanocomposites was conducted by magnesium activation under nitrogen atmosphere at 400 °C and 500 °C. The characterization of different materials was performed using various modern instruments such as XPS, SEM, EDS, XRD, FT-IR, BET…The comparison between modified and unmodified biochars for removing NH4+ and PO43− from water and the impact of different parameters on adsorption capacity of obtained materials were also performed. The results showed that the activation of biochar by magnesium led to changes in surface areas, pore volume, surface charge, and chemical properties of biochars and to increases in NH4+ and PO43− adsorption capacity. The adsorption of NH4+ and PO43− onto biochar-based nanocomposites followed both chemisorption and physisorption, were spontaneous, and endothermic. The NH4+ maximum uptake calculated according to Langmuir model were 21.32 mg/g for RMgN500 and 16.31 mg/g for CMgN500 while the PO43− maximum uptake were 117.77 mg/g and 52.24 mg/g for of RMgN500 and CMgN500, respectively. The desorption and recyclability of the RMgN500 and CMgN500 were very effective by using 0.5 M NaOH solution for PO43− and diluted HCl solutions for NH4+. This approach of synthesizing MgO nanoparticles impregnated in biochar matrix provided new opportunities in developing low-cost and highly efficient adsorbent to removal and recovery of NH4+ and PO43− from water.

Recovery of NH4 +-N and PO4 3--P from urine using sludge-derived biochar as a fertilizer: performance and mechanism.

Sludge-derived biochar (BS) was prepared by pyrolyzing municipal sludge at different temperatures and was used to recover NH4+–N and PO43−–P from urine. The effects of dosage, adsorption time, and urine concentration on the adsorption of NH4+–N and PO43−–P were investigated, and the adsorbed BS was used as a fertilizer to study its effect on the growth of pakchoi cabbage. The Elovich model was more consistent with the adsorption processes of NH4+–N and PO43−–P. Both the NH4+–N and PO43−–P adsorption isotherm model agreed with the Redlich–Peterson model. The Langmuir model showed that the largest adsorption capacity of BS600 for NH4+–N and PO43−–P could reach 114.64 mg g−1 and 31.05 mg g−1, respectively. The NH4+–N adsorption mechanism of BS may have complexation with O-containing functional groups and precipitation reactions, while the removal mechanism of PO43−–P was co-precipitation. The pot experiment demonstrated that adsorbed BS600 can better promote the growth of pakchoi cabbage with the same amount of addition. With the addition of 5% adsorbed BS600, the weight of cabbage was 64.49 g heavier than without the addition of BS600. This research provided theoretical support for the recovery of NH4+–N and PO43−–P from urine as a fertilizer.

Treatment of wastewater containing high concentrations of ammonia nitrogen using ion exchange resins

AbstractNitrogen in water will induce active biogeochemical effects, such as denitrification and anammox, which release N2O, a greenhouse gas, leading to increasing global warming. Therefore, it is necessary to find an economical and efficient method to treat ammonia nitrogen in the field of wastewater treatment. In this study, two cation exchange resins, D61 and D708, were selected to analyze external environment conditions suitable for the adsorption of ammonia nitrogen by conducting orthogonal experiments. The kinetic and thermodynamic mechanisms were discussed, and cation exchange resins with a high selectivity to NH4+ were selected. The optimum adsorption temperature, pH, and rotation speed for the D61 resin were found to be 32°C, 5, and 150 r/min, respectively. The optimum adsorption temperature and rotation speed for the D708 resin were 40°C and 150 r/min, respectively. The kinetic data could be accurately described using the pseudo‐second‐order kinetic equation. The results showed that physical and chemical adsorption mechanisms may coexist in the adsorption of NH4+‐N. The adsorption process can easily occur and that it is not limited by the pH or rotational speed. The maximum adsorption capacities of the D61 and D708 resins were 44.93 and 31.34 mg/g, respectively; removing ammonia nitrogen from 1 m3 of wastewater requires only 100–110 g of ion exchange resin. The cost is $1.78/m3 of raw wastewater treated. This is a good alternative to other nitrogen removal systems, particularly in comparison with conventional physicochemical methods and the nitrification–denitrification biochemical process employed currently.

Effect of Mangrove Biochar Residue Amended Shrimp Pond Sediment on Nitrogen Adsorption and Leaching

Mangrove biochar residue was used for nitrogen adsorption and retention in sediment, which is beneficial for plant germination. The present study investigated the effect of contact time (5–360 min), biochar dosage (0.2–2 g L−1), pH (5–6), and initial concentration (2–10 mg L−1) on NH4+-N and NO3−-N adsorption. Three different adsorption isotherm models were used to fit the experimental data. Column leaching experiments were conducted to investigate the effect of biochar with sediment from a shrimp pond on nitrogen leaching at varying biochar dosages (0–8% w/w). The results showed that the maximum percentage of both NH4+-N and NO3−-N adsorption was achieved at an equilibrium contact time of 240 min, with an adsorbent dosage of 2 g L−1, and pH at 5.5 and 5, respectively. The adsorption of NH4+-N and NO3−-N were fitted to the Freundlich model and the adsorption process followed the physisorption and ion exchange. The addition of 8% biochar reduced both cumulative water volume and nitrogen leaching from the sediment. The biochar amendment increased the relative abundance of nitrifying and denitrifying bacteria in the sediment. This result suggested that biochar amended with sediment could be useful for nitrogen loss reduction.

Biochar and urea co-application regulates nitrogen availability in soil

Overuse of nitrogenous fertilizers especially urea has been considered a significant source of reactive N causing acute environmental impacts through leaching, volatilization, and N2O gas emission from fertilized crop fields. However, some recent studies have proposed that such environmental losses of N can be ignored by adapting an alternative way of combining nitrogenous fertilizer with pyrolyzed biomass (biochar). Therefore, the effect of co-application of rice-residue biochar (RB) or poultry manure biochar (PB) along with urea on N dynamics was investigated by conducting a 60-day incubation experiment. The results showed that urea led to greater N mineralization (0.2µgNg-1 soil day-1) due to the easy availability of ammonical-N (NH4+-N) produced from hydrolysis that acted as a substrate for nitrification. Sole application of biochars (RB or PB) or their co-application with urea resulted in 38-45% and 19-28% lower N mineralization than the sole urea amended soil, respectively. The lower N mineralization in sole biochar or biochar plus urea amended soil was most likely caused due to (1) increased C:N ratio of the biochar amended soil, (2) adsorption of NH4+-N by biochar, (3) microbial immobilization of the nitrogen in the amended soil, and (4) lower urease activity in the treatments amended with biochar. Thus, it may be concluded that the co-application of biochar with urea can reduce N losses through moderation of N mineralization and make it available to plants for longer periods.