Removal of nitrate from aqueous solution by modified sugarcane bagasse biochar

Adsorption characteristics of S-Metolachlor onto the sawdust biochar derived from Acacia auriculiformis

The adsorption mechanism of S-Metolachlor in an aqueous solution by sawdust biochar derived from Acacia auriculiformis (SAB) was studied. SAB was manufactured at 500 °C for 4 h under oxygen-limited conditions and characterized for SEM, EDS, pHpzc, BET, and FTIR. The adsorption kinetics, isotherm, and diffusion studies of S-Metolachlor and SAB were further explored. Moreover, the effects of the solution pH were examined on the adsorption of S-Metolachlor by SAB. The BET analysis of SAB was achieved at 106.74 m2.g-1 and the solution pH did not significantly influence the S-Metolachlor adsorption. The adsorption data were fitted into a Langmuir isotherm and the PSO model. The film diffusion coefficient Df (4.93 × 10-11 to 8.17 × 10-11 m2.s-1) and the particle diffusion coefficient Dp (1.68 × 10-11 to 2.65 × 10-11 m2.s-1) were determined and the rate-limiting step of S-Metolachlor adsorption and SAB was governed by liquid film diffusion. The S-Metolachlor adsorption process onto SAB was controlled by multiple mechanisms, including pore filling, H-bonding, hydrophobic interaction, and π-π EDA interactions. H-bonding is the main interaction for the adsorption of S-Metolachlor and SAB. Conclusively, the study illustrates that biochar produced from Acacia auriculiformis sawdust possessed effective adsorption properties for S-Metolachlor herbicide.

Selective adsorption of nitrate in water by organosilicon quaternary ammonium salt modified derived nickel-iron layered double hydroxide: Adsorption characteristics and mechanism

Nitrate (NO3-) is a widespread pollutant in the water environment. Due to its physicochemical properties, such as negative monovalent charge, traditional adsorption treatment processes have low selectivity for NO3- removal, resulting in low removal efficiency of NO3- by adsorbents in the presence of interfering ions. Therefore, to improve the adsorption selectivity and efficiency of NO3-. In this study, we used organosilicon quaternary modified derived nickel-iron layered double hydroxide (NiFe-MLDH/OQAS) for selective removal of NO3-. NiFe-MLDH/OQAS has a flowery globular structure, with interconnected nanosheets on the surface providing more adsorption sites for NO3-, which improves the adsorption rate and adsorption amount. What's more, the nitrate removal rate of NiFe-MLDH/OQAS only decreased by about 14.36% in the presence of the same concentration of interfering ions, and the maximum adsorption amount reached 61.05 mg/g, showing good selectivity and adsorption amount. Various characterization analyses indicate that the nitrate selectivity of NiFe-MLDH/OQAS is attributed to its unique layer spacing, as well as the abundant functional groups on the material surface. Finally, we demonstrated through experiments that NiFe-MLDH/OQAS has good cyclic regeneration ability and environmental safety. These findings demonstrate the great potential of NiFe-MLDH/OQAS for selective adsorption of NO3-.

Nitrate-Nitrogen Adsorption Characteristics and Mechanisms of Various Garden Waste Biochars

Nitrate-nitrogen (NO3--N) removal and garden waste disposal are critical concerns in urban environmental protection. In this study, biochars were produced by pyrolyzing various garden waste materials, including grass clippings (GC), Rosa chinensis Jacq. branches (RC), Prunus persica branches (PP), Armeniaca vulgaris Lam. branches (AV), Morus alba Linn. sp. branches (MA), Platycladus orientalis (L.) Franco branches (PO), Pinus tabuliformis Carrière branches (PT), and Sophorajaponica Linn. branches (SL) at three different temperatures (300 °C, 500 °C, and 700 °C). These biochars, labeled as GC300, GC500, GC700, and so on., were then used to adsorb NO3--N under various conditions, such as initial pH value, contact time, initial NO3--N concentration, and biochar dosage. Kinetic data were analyzed by pseudo-first-order and pseudo-second-order kinetic models. The equilibrium adsorption data were evaluated by Langmuir, Freundlich, Temkin and Dubinin-Radushkevich models. The results revealed that the biochar yields varied between 14.43% (PT700) and 47.09% (AV300) and were significantly influenced by the type of garden waste and decreased with increasing pyrolysis temperature, while the pH and ash content showed an opposite trend (p < 0.05). The efficiency of NO3--N removal was significantly influenced by the type of feedstock, preparation process, and adsorption conditions. Higher pH values had a negative influence on NO3--N adsorption, while longer contact time, higher initial concentration of NO3--N, and increased biochar dosage positively affected NO3--N adsorption. Most of the kinetic data were better fitted to the pseudo-second-order kinetic model (0.998 > R2 > 0.927). Positive b values obtained from the Temkin model indicated an exothermic process of NO3--N adsorption. The Langmuir model provided better fits for more equilibrium adsorption data than the Freundlich model, with the maximum NO3--N removal efficiency (62.11%) and adsorption capacity (1.339 mg·g-1) in PO700 under the conditions of pH = 2, biochar dosage = 50 mg·L-1, and a reaction time of 24 h. The outcomes of this study contribute valuable insights into garden waste disposal and NO3--N removal from wastewater, providing a theoretical basis for sustainable environmental management practices.

Bio-Based Adsorption as Ecofriendly Method for Wastewater Decontamination: A Review

Intense human activities have for years contributed to the pollution of the environment by many dangerous pollutants such as heavy metals, pesticides, or polycyclic aromatic hydrocarbons. There are many conventional methods used to control pollution, with practical and/or financial drawbacks. Therefore, in recent years, an innovative, easy-to-implement and inexpensive adsorption method has been developed to recover waste and clean up water from micropollutants. Firstly, this article aims to summarize the issues related to water remediation and to understand the advantages and disadvantages of the methods classically used to purify water. In particular, this review aims to provide a recent update of the bio-based adsorbents and their use. Differently from the majority of the reviews related to wastewater treatment, in this article several classes of pollutants are considered. Then, a discussion about the adsorption process and interactions involved is provided. Finally, perspectives are suggested about the future work to be done in this field.

An application of waste algae biochar in aquaculture water to remove co-existed cadmium and PAHs and the corresponding mechanism

Water quality in aquaculture farms is highly related to the quality of aquaculture products and the connected environment. Cadmium (Cd²⁺) and polycyclic aromatic hydrocarbons (PAHs) are two of the most common pollutants in the aquaculture water, while biochar derived from waste algae (Enteromorpha prolifera), namely BE, was applied in farms ponds to improve water quality. Firstly, the adverse environmental impact of BE was minor, while the concentrations of the heavy metal (Cd²⁺ in the present study) and PAHs (FLU, PHE, FLT and PYR) were removed with efficiencies of 49%, 88%, 90%, 91% and 88%, respectively. The ecological risk values (RQs) were reduced subsequently with a rate of 58 ± 11%. After dosing BE, the ecological risk values in all the studied ponds were lower than 1, indicating no ecological risk in the corresponding aquaculture environment. The sorption capacities (q_m) of BE were 15, 12, 6.3, 0.41, 0.29 and 0.56 mg·g^-1 for Cd²⁺, FLU, PHE, FLT, PYR and BaP, respectively. The sorption capacities were acceptable compared with those derived from other types of biomass. The removal mechanisms were partition (PAHs), complexation (Cd²⁺), π-π interaction (Cd²⁺ and PAHs), precipitation (Cd²⁺) and ion-exchange (Cd²⁺). Practically and theoretically, the algae biochar is applicable in the aquaculture environment, where Cd²⁺ and PAHs co-exist.

A feasibility study on production, characterisation and application of empty fruit bunch oil palm biochar for Mn2+ removal from aqueous solution

Empty fruit bunch oil palm (EFBOP) is one of the byproducts after oil palm fruitlet is removed in oil palm processing and is considered as waste. In this study, EFBOP was converted to biochar (BC-EFBOP) at 350-700 °C, with an overarching aim of determining the feasibility of adsorptive removal of manganese (a second dominant element in acid mine drainage) from water. Results showed that with increasing temperature, the BC-EFBOP yield decreased from 44.34% to 26.74%, along with the H/C (0.89%-0.29%) and O/C ratios (0.38%-0.23%), and the carbon content increased (62.7%-73.93%). As evidenced by Fourier Transform InfraRed spectroscopy (FTIR) and X-ray Photoelectron Spectroscopy (XPS), abundant oxygen-containing surface functional groups such as hydroxyl (-OH), carboxyl (-COOH), and ether (C-O-C) were retained, and aromatic CC groups were largely generated in the biochar. Pyrolysed biochar at 350 °C (BC350), with the least surface area (0.5 m² g^-1), exhibited the highest Mn²⁺ adsorption capacity (8.2 mg g^-1), whereas for BC700, with the largest surface area (2.19 m² g^-1), had the lowest capacity for Mn²⁺ (1.2 mg g^-1). Regardless of the temperature, solution pH of 5 was found to be optimal for Mn²⁺ removal from water. The Langmuir isotherm model best described the equilibrium adsorption data with a maximum adsorption capacity of 1.2-8.2 mg g^-1 for initial concentrations of 5-250 mg L^-1, whereas the adsorption kinetics followed the pseudo-second-order model. There was nearly four-fold increase in Mn²⁺ ions removal with increased biochar dosage (0.05-0.5 g), at initial Mn²⁺ concentration of 100 mg L^-1. The study showed that a low-cost, environmentally friendly BC-EFBOP with optimal surface chemistry could potentially remediate Mn²⁺ ions from aqueous media. However, a proper cost-benefit and techno-economic analysis is needed prior to potential pilot scale studies.

Appraising the performance of oil palm fibre biochar for low concentration ammoniacal nitrogen recovery from aquaculture wastewater

Oil palm fibre is a type of solid waste generated from palm oil processing plant. At present, there is no proper utilization of this abundant waste. Ammoniacal nitrogen (NH3-N) has received a lot of attention as a water pollutant due to its toxicity, which has an impact on both the environment and human health. In aquaculture wastewater (AQW), NH3-N is present in low concentrations (<10 ppm), and removing low concentrations of NH3-N is tedious. Thus, this study focuses on the potential of oil palm fibre biochar (OPFB) for sustainable low concentration NH3-N recovery from AQW and the recovered spent adsorbent to be used as a bio-fertilizer. The Physico-chemical properties of OPFB show a positive correlation with NH3-N recovery. A significant reduction of value-added metals in OPFB has confirmed the recovery of NH3-N through the ion exchange process. The adsorption isotherms and kinetics of NH3-N recovery had good correlation coefficients under the Freundlich and pseudo-second-order kinetic model confirming a multilayer heterogeneous and chemical adsorption respectively. Thermodynamic parameters indicated that the recovery process via adsorption was exothermic and had a Physio-chemical mechanism. At optimum conditions, OPFB could recover up to 66% of NH3-N actual AQW. The properties of spent OPFB showed potential reutilization as a soil amendment agent or biofertilizer which could be easily degraded.

From waste to fertilizer: Nutrient recovery from wastewater by pristine and engineered biochars

Biochar application for the recovery of nutrients from wastewater is a sustainable method based on a circular economy. Wastewater, food wastewater, and stormwater are valuable sources of nutrients (i.e., PO₄^3-, NO₃^-, and NH₄⁺). The unique properties of biochar, such as its large specific surface area, pH buffering capacity, and ion-exchange ability, make it a cost-effective and environmentally friendly adsorbent. Biochar engineering improves biochar properties and provide targeted adsorbents. The biochar-based fertilizers can be a sustainable alternative to traditional fertilization. The aim of the study was to compare the potential of pristine and engineered biochars to recover nutrients from wastewater and to determine the factors which may affect this process. Engineered biochar can be used as a selective adsorbent from multicomponent solutions. Adsorption on engineered biochar can be also regulated by additional mechanisms: surface precipitation and ligand/ion exchange. Metal modification (e.g. Mg, Fe) enhances PO₄^3- and NO₃^- adsorption capacity, and thus may provide the extra plant macro-/micronutrients. The desorption mechanism, which is the basis for nutrient release are strongly pH depended. The use of biochar-based fertilizer can have economic and agricultural benefits when using waste materials and reducing pyrolysis energy costs.

Physical-Chemical Characterization of Different Carbon-Based Sorbents for Environmental Applications

Biochar has been used in various applications, e.g., as a soil conditioner and in remediation of contaminated water, wastewater, and gaseous emissions. In the latter application, biochar was shown to be a suitable alternative to activated carbon, providing high treatment efficiency. Since biochar is a by-product of waste pyrolysis, its use allows for compliance with circular economics. Thus, this research aims to obtain a detailed characterization of three carbonaceous materials: an activated carbon (CARBOSORB NC 1240^®) and two biochars (RE-CHAR^® and AMBIOTON^®). In particular, the objective of this work is to compare the properties of three carbonaceous materials to evaluate whether the application of the two biochars is the same as that of activated carbon. The characterization included, among others, particle size distribution, elemental analysis, pH, scanning electron microscope, pore volume, specific surface area, and ionic exchange capacity. The results showed that CARBOSORB NC 1240^® presented a higher specific surface (1126.64 m²/g) than AMBIOTON^® (256.23 m²/g) and RE-CHAR^® (280.25 m²/g). Both biochar and activated carbon belong to the category of mesoporous media, showing a pore size between 2 and 50 nm (20-500 Å). Moreover, the chemical composition analysis shows similar C, H, and N composition in the three carbonaceous materials while a higher O composition in RE-CHAR^® (9.9%) than in CARBOSORB NC 1240 ^® (2.67%) and AMBIOTON^® (1.10%). Differences in physical and chemical properties are determined by the feedstock and pyrolysis or gasification temperature. The results obtained allowed to compare the selected materials among each other and with other carbonaceous adsorbents.

Applications of soft computing techniques for prediction of pollutant removal by environmentally friendly adsorbents (case study: the nitrate adsorption on modified hydrochar)

Artificial intelligence has emerged as a powerful tool for solving real-world problems in various fields. This study investigates the simulation and prediction of nitrate adsorption from an aqueous solution using modified hydrochar prepared from sugarcane bagasse using an artificial neural network (ANN), support vector machine (SVR), and gene expression programming (GEP). Different parameters, such as the solution pH, adsorbent dosage, contact time, and initial nitrate concentration, were introduced to the models as input variables, and adsorption capacity was the predicted variable. The comparison of artificial intelligence models demonstrated that an ANN with a lower root mean square error (0.001) and higher R² (0.99) value can predict nitrate adsorption onto modified hydrochar of sugarcane bagasse better than other models. In addition, the contact time and initial nitrate concentration revealed a higher correlation between input variables with the adsorption capacity.

Removal of the Harmful Nitrate Anions from Potable Water Using Different Methods and Materials, including Zero-Valent Iron

Drinking water containing nitrate ions at a higher concentration level of more than 10 mg/L, according to the World Health Organization (WHO), poses a considerable peril to humans. This danger lies in its reduction of nitrite ions. These ions cause methemoglobinemia during the oxidation of hemoglobin into methemoglobin. Many protocols can be applied to the remediation of nitrate ions from hydra solutions such as Zn metal and amino sulfonic acid. Furthermore, the electrochemical process is a potent protocol that is useful for this purpose. Designing varying parameters, such as the type of cathodic electrode (Sn, Al, Fe, Cu), the type of electrolyte, and its concentration, temperature, pH, and current density, can give the best conditions to eliminate the nitrate as a pollutant. Moreover, the use of accessible, functional, and inexpensive adsorbents such as granular ferric hydroxide, modified zeolite, rice chaff, chitosan, perlite, red mud, and activated carbon are considered a possible approach for nitrate removal. Additionally, biological denitrification is considered one of the most promising methodologies attributable to its outstanding performance. Among these powerful methods and materials exist zero-valent iron (ZVI), which is used effectively in the deletion process of nitrate ions. Non-precious synthesis pathways are utilized to reduce the Fe²⁺ or Fe³⁺ ions by borohydride to obtain ZVI. The structural and morphological characteristics of ZVI are elucidated using UV–Vis spectroscopy, zeta potential, XRD, FE-SEM, and TEM. The adsorptive properties are estimated through batch experiments, which are achieved to control the feasibility of ZVI as an adsorbent under the effects of Fe⁰ dose, concentration of NO₃⁻ ions, and pH. The obtained literature findings recommend that ZVI is an appropriate applicant adsorbent for the remediation of nitrate ions.

Modified Hazelnut Shells as a Novel Adsorbent for the Removal of Nitrate from Wastewater

The aim of the study was to prepare a novel adsorbent by chemical modification of hazelnut shells and evaluate its potential for the nitrate removal from model solutions and real wastewater. The characterization of the novel adsorbent, i.e., modified hazelnut shell (MHS) was performed. The adsorbent characterization included the analysis of elemental composition and the surface characteristics analysis by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). The adsorption experiments (batch technique) were performed to investigate the effects of adsorbent concentration, contact time, initial nitrate concentration, and solution pH. The nitrate removal efficiency increased with the increase in MHS concentration and decreased with the initial nitrate concentration. MHS was found to be effective in nitrate removal over a wide pH range (from 2 to 10), and the highest amount of nitrate adsorbed was 25.79 mg g−1 in a model nitrate solution. Depending on the aqueous medium (model solutions or real wastewater samples), it was shown that both Langmuir and Freundlich adsorption isotherm models can be used to interpret the adsorption process. It was found that the kinetics are well described by a pseudo-second order model and the nitrate adsorption process can be controlled by chemisorption. The intraparticle diffusion model has been used to identify an adsorption-controlled process by diffusion mechanisms. Adsorption/desorption experiments in column confirmed that MHS could be successfully used in multiple cycles (at least three), indicating the potential of MHS as an alternative to costly commercial adsorbents for the removal of nitrates from wastewater.

Recycling sludge-derived hydrochar to facilitate advanced denitrification of secondary effluent: Role of extracellular electron transfer

Sludge-derived hydrochar (SDHC) was recycled to enhance the denitrification of secondary effluent. Under different carbon to nitrogen (C/N) ratios, the nitrogen removal efficiency (NRE) and carbon source efficiency (CSE) of denitrification coupled with SDHC (DN-SDHC) were distinctly higher than that of denitrification alone (DN). Moreover, at the C/N ratios of 3.0-3.2 and 5.8-5.9, the nitrogen removal rate (NRR) of DN-SDHC was 3.6- and 1.5-fold that of DN, respectively. The characterization of SDHC before and after used in denitrification indicated that the metal ions and functional groups did not participate in denitrification. Although SDHC has no redox capacity to donate electron for denitrification, its higher conductivity enabled the acceleration of extracellular electron transfer from carbon source to denitrifiers. The abundance of denitrifying community and functional genes was synchronously promoted by SDHC. Especially, the significant increase of nosZ gene encoding nitrous oxide reductase was conducive to mitigating the emission of N₂O greenhouse gas.

Recent advancements on biochars enrichment with ammonium and nitrates from wastewaters: A critical review on benefits for environment and agriculture

During the last decade, biochars have been considered as attractive and eco-friendly materials with various applications including wastewater treatment, energy production and soil amendments. However, the important nitrogen losses during biochars production using the pyrolysis process have limited their potential use in agriculture as biofertilizer. Therefore, it seems necessary to enrich these biochars with nitrogen sources before their use in agricultural soils. This paper is the first comprehensive review on the assessment of biomass type and the biochars' properties effects on N recovery efficiency from aqueous solutions as well as its release and availability for plants when applying the N-enriched chars in soils. In particular, the N recovery efficiency by raw biochars versus the type of the raw feedstock is summarized. Then, correlations between the adsorption performance and the main physico-chemical properties are established. The main mechanisms involved during ammonium (NH₄-N) and nitrates (NO₃-N) recovery process are thoroughly discussed. A special attention is given to the assessment of the biochars physico-chemical modification impact on their N recovery capacities improvement. After that, the application of these N-enriched biochars in agriculture and their impacts on plants growth as well as methane and nitrous oxide greenhouse gas emissions reduction are also discussed. Finally, the main future development and challenges of biochars enrichment with N from wastewaters and their valorization as biofertilizers for plants growth and greenhouse gas (GHG) emissions reduction are provided. This systematic review is intended to promote the real application of biochars for nutrients recovery from wastewaters and their reuse as eco-friendly fertilizers.

Preparation of N,S-codoped magnetic bagasse biochar and adsorption characteristics for tetracycline

Agricultural waste disposal and purification of polluted water are always the key issues of environmental restoration. In this work, thiourea-functionalized magnetic bagasse biochar (MFeBC) was prepared for tetracycline (TC) removal from aqueous solutions. Firstly, MFeBC was prepared by a combined impregnation and chemical coprecipitation method. Furthermore, MFeBC was characterized by Brunauer–Emmett–Teller surface area analysis, Fourier transform infrared spectrometry, X-ray diffraction analysis, scanning electron microscopy, X-ray photoelectron spectroscopy and the magnetic hysteresis curves. For the TC adsorption, the effects of different solution pH level, adsorbent dosage, initial TC concentration and temperature on the adsorption performance were studied respectively. Moreover, the results indicated that the Freundlich isotherm models appropriately described the adsorption process. The kinetic data were better fitted by the pseudo-second-order kinetic model. The maximum TC adsorption capacity of MFeBC reached 69.26 mg g⁻¹. Hydrogen bonding and Π–Π interactions played a dominant role in the adsorption process. Therefore, MFeBC can be used as an effective adsorbent for tetracycline removal from aqueous solution.

Preparation of N,S-codoped magnetic bagasse biochar and adsorption of tetracycline.

Adsorption and desorption of nutrients from abattoir wastewater: modelling and comparison of rice, coconut and coffee husk biochar

Enrichment of water bodies with nutrients from wastewater is one of the causes of eutrophication to aquatic ecosystems. This study investigated the use of biochar derived from rice husk, coconut husk, and coffee husk in adsorbing nitrates (NO3-N) and nitrites (NO2-N) from slaughterhouse wastewater. It also explored the desorption efficiencies of the adsorbed nutrients to ascertain the applicability of the enriched biochars as slow-release fertilizers. To characterize the physicochemical properties of the biochars, scanning electron microscopy (SEM) was used. Fourier transforms infrared spectroscopy (FTIR), elemental analysis (CHNO) Langmuir and Freundlich, and the isotherm models were employed to fit the experimental equilibrium adsorption data. It was observed that the Langmuir isotherm model has the best fit of NO3- N and NO2- N on all the biochars. And this was based on the coefficient of correlation values. Also, the coconut husk biochar has the highest adsorption capacities of NO3-N and NO2-N at 12.97 mg/g, and 0.244 mg/g, respectively, attributing to its high porosity as revealed by the SEM images. The adsorption capacities for the rice husk char were 12.315 and 0.233 mg/g, while that for coffee husk char were12.08 mg/g and 0.218 mg/g for NO3-N and NO2-N, respectively. The relatively higher amount of NO3-N adsorbed to that of NO2-N could be attributed to its higher initial concentration in the solution than nitrite concentration. The desorption efficiencies of nitrates were 22.4, 24.39, and 16.79 %, for rice husk char, coconut husk char and coffee husk char, respectively. For the rice husk char, coconut husk char and coffee husk char, the nitrites desorption efficiencies were 80.73, 91.39, and 83.62 %, respectively. These values are good indicators that the studied biochar can be enriched with NO3- N and NO2- N and used as slow-release fertilizers.

Application of Modified Spent Mushroom Compost Biochar (SMCB/Fe) for Nitrate Removal from Aqueous Solution

The public is already aware that nitrate pollution caused by nutrient runoff from farms is harmful to aquatic life and human health, and there is an urgent need for a product/technology to solve this problem. A biochar adsorbent was synthesized and used to remove nitrate ions from aqueous media based on spent mushroom compost (SMC), pre-treated with iron (III) chloride hexahydrate and pyrolyzed at 600 °C. The surface properties and morphology of SMCB/Fe were investigated using Fourier transform-infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The effect of main parameters such as the adsorbent dosages, pH of the solutions, contact times, and ion concentrations on the efficiency of nitrate removal was investigated. The validity of the experimental method was examined by the isothermal adsorption and kinetic adsorption models. The nitrate sorption kinetics were found to follow the pseudo-second-order model, with a higher determination coefficient (0.99) than the pseudo-first-order (0.86). The results showed that the maximum percentage of nitrate adsorption was achieved at equilibrium pH 5-7, after 120 min of contact time, and with an adsorbent dose of 2 g L-1. The highest nitrate adsorption capacity of the modified adsorbent was 19.88 mg g-1.

Biochar-supported polyaniline hybrid for aqueous chromium and nitrate adsorption

Biochar adsorbents can remove environmental pollutants and the remediation of Cr(VI) and nitrate are considered. Cr(VI) is a proven carcinogen causing serious health issues in humans and nitrate induced eutrophication causes negative effect on aquatic systems around the world. Douglas fir biochar (DFBC), synthesized by fast pyrolysis during syn gas production, was treated with aniline. Then, a polyaniline biochar (PANIBC) composite containing 47 wt% PANI was prepared by precipitating PANI on DFBC surfaces by oxidative chemical polymerization of aniline in 2M HCl. PANIBC exhibited a point of zero charge (PZC) of 3.0 and 8.2 m²/g BET (N₂) surface area. This modified biochar was characterized by thermogravimetric analysis (TGA), scanning electron microscopy (SEM) morphology and surface elements, and oxidation states by X-ray photoelectron spectroscopy (XPS). PANIBC exhibited positive surface charge below pH 3, making it an outstanding adsorbent, for Cr(VI) removal. Cr(VI) and nitrate removal mechanisms are presented based on XPS analysis. DFBC and PANIBC Cr(VI) and nitrate adsorption data were fitted to Langmuir and Freundlich isotherm models with maximum Langmuir adsorption capacities of 150 mg/g and 72 mg/g, respectively. Cr(VI) and nitrate removal at pH 2 and 6 were evaluated by reducing the amount of PANI (9 wt%) dispersed on to DFBC. Adsorption capacities verses temperature studies revealed that both Cr(VI) and nitrate adsorption are endothermic and thermodynamically favored. Regeneration studies were conducted on both DFBC and PANIBC using 0.1M NaOH and PANIBC exhibited excellent sorption capacities for Cr(VI) and nitrate in lake water samples and in the presence of competitive ions.

Sugarcane bagasse: a biomass sufficiently applied for improving global energy, environment and economic sustainability

Sugarcane (Saccharum officinarum) bagasse (SCB) is a biomass of agricultural waste obtained from sugarcane processing that has been found in abundance globally. Due to its abundance in nature, researchers have been harnessing this biomass for numerous applications such as in energy and environmental sustainability. However, before it could be optimally utilised, it has to be pre-treated using available methods. Different pre-treatment methods were reviewed for SCB, both alkaline and alkali-acid process reveal efficient and successful approaches for obtaining higher glucose production from hydrolysis. Procedures for hydrolysis were evaluated, and results indicate that pre-treated SCB was susceptible to acid and enzymatic hydrolysis as > 80% glucose yield was obtained in both cases. The SCB could achieve a bio-ethanol (a biofuel) yield of > 0.2 g/g at optimal conditions and xylitol (a bio-product) yield at > 0.4 g/g in most cases. Thermochemical processing of SCB also gave excellent biofuel yields. The plethora of products obtained in this regard have been catalogued and elucidated extensively. As found in this study, the SCB could be used in diverse applications such as adsorbent, ion exchange resin, briquettes, ceramics, concrete, cement and polymer composites. Consequently, the SCB is a biomass with great potential to meet global energy demand and encourage environmental sustainability.

Effect of two types of adsorption sites of activated carbon fibers on nitrate ion adsorption

In this study, the activation with ZnCl₂ and heat treatment at 950 °C were performed to polyacrylonitrile-based carbon fiber and phenol resin to prepare two types of activated carbon fibers (ACFs) with different amounts of quaternary nitrogen (N-Q). In order to investigate the effect of chemical properties of ACFs on nitrate adsorption, various experiments and assess were conducted on these samples. The pH_pzc of Py-7.0Z4-9.5HT10 and PhR-6.0Z4-9.5HT30 was about 7.1 and 7.0, respectively, and was no significant difference in the results. The C-π sites had a large effect on the amount of nitrate adsorption, and its adsorption capacity was greatest when the solution pH was about 3. However, the adsorption affinity (K_e) of C-π sites was weaker than that of N-Q, and the contribution for adsorption was small when the solution was low concentration or neutral, while the N-Q was the dominant adsorption site of ACFs. It is expected that the N-Q affected the adsorption kinetics, and the higher the amount of N-Q, the faster the adsorption rate. Py-7.0Z4-9.5HT10 had a large amount of C-π sites and N-Q. Therefore, the equilibrium adsorption amount (Q_e) of Py-7.0Z4-9.5HT10 was 1.02 mmol/g at solution pH 3, and the adsorption kinetics were also fast.

Influence of water washing treatment on Ulva prolifera-derived biochar properties and sorption characteristics of ofloxacin

The influences of water washing treatment on the properties of Ulva prolifera-derived biochar (U.P-biochar) and its sorption characteristics of ofloxacin (OFL) were investigated. The results showed that the water washing treatment significantly changed the physiochemical structures of U.P-biochars, and improved the sorption capacity of OFL. The sorption capacity of OFL by U.P-biochar was closely dependent on pyrolysis temperature (200-600 °C) and equilibrium solution pH (3-11). Different sorption mechanisms (e.g. cation exchange, electrostatic attraction, H-bond and cationic-π and π-π interactions) were dominant for specific U.P-biochars under various pH regions (acidic, neutral and alkaline). Moreover, the unwashed and washed U.P-biochars prepared at 200 °C (BC200 and BCW200) showed a higher sorption capacity of OFL at pH = 7. The two-compartment first-order model provided an appropriate description of the sorption kinetics of OFL by BC200 and BCW200 (R2 > 0.98), which revealed that the contribution ratios between the fast and slow sorption compartments (ffast/fslow, 1.55 for BC200 and 1.25 for BCW200) reduced after water washing treatment of U.P-biochar. The values of n for the Freundlich model were less than 1, which demonstrated that the sorption of OFL by BC200 and BCW200 was favourable and nonlinear. Also, the sorption of OFL by BC200 and BCW200 increased with an increase in solution temperature and the sorption process was spontaneous and endothermic. This study provides valuable information for being a primary consideration in the production and application of U.P-biochar.

Current and Emerging Adsorbent Technologies for Wastewater Treatment: Trends, Limitations, and Environmental Implications

Wastewater generation and treatment is an ever-increasing concern in the current century due to increased urbanization and industrialization. To tackle the situation of increasing environmental hazards, numerous wastewater treatment approaches are used—i.e., physical, chemical, and biological (primary to tertiary treatment) methods. Various treatment techniques being used have the risks of producing secondary pollutants. The most promising technique is the use of different materials as adsorbents that have a higher efficacy in treating wastewater, with a minimal production of secondary pollutants. Biosorption is a key process that is highly efficient and cost-effective. This method majorly uses the adsorption process/mechanism for toxicant removal from wastewater. This review elaborates the major agricultural and non-agricultural materials-based sorbents that have been used with their possible mechanisms of pollutant removal. Moreover, this creates a better understanding of how the efficacy of these sorbents can be enhanced by modification or treatments with other substances. This review also explains the re-usability and mechanisms of the used adsorbents and/or their disposal in a safe and environmentally friendly way, along with highlighting the major research gaps and potential future research directions. Additionally, the cost benefit ratio of adsorbents is elucidated.

Nitrate removal from aqueous solutions by cobalt ferrite nanoparticles synthesized by co-precipitation method: isotherm, kinetic and thermodynamic studies

The purpose of this study was to examine the nitrate adsorption by cobalt ferrite (CFO) nanoparticles. The adsorbent was synthesized by co-precipitation method and its structure was characterized using scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction and vibrating-sample magnetometry. In batch adsorption studies, the effects of various parameters like pH (3-11), adsorbent dose (0.2-0.8 g/L), contact time (5-120 min), initial nitrate concentration (50-200 mg/L), and temperature (283-313 K) on the adsorption process were examined. The results of this study indicated that the maximum adsorption capacity was 107.8 mg/g (optimum condition pH = 3, adsorbent dosage: 0.2 g/L, nitrate concentration: 200 mg/L, contact time: 20 min and temperature: 313 K). The adsorption isotherm had a proper match with Langmuir (R² = 0.99) and Freundlich (R² = 0.99) models. The adsorption of nitrate by CFO followed pseudo-second-order kinetics. The results of the thermodynamics of the nitrate adsorption process by CFO showed that all the values of Gibbs free energy change, enthalpy change and entropy change were positive. Therefore, this process was endothermic and non-spontaneous.

Removal of Zn(II), Mn(II) and Cu(II) by adsorption onto banana stalk biochar: adsorption process and mechanisms

Low-cost banana stalk (Musa nana Lour.) biochar was prepared using oxygen-limited pyrolysis (at 500 °C and used), to remove heavy metal ions (including Zn(II), Mn(II) and Cu(II)) from aqueous solution. Adsorption experiments showed that the initial solution pH affected the ability of the biochar to adsorb heavy metal ions in single- and polymetal systems. Compared to Mn(II) and Zn(II), the biochar exhibited highly selective Cu(II) adsorption. The adsorption kinetics of all three metal ions followed the pseudo-second-order kinetic equation. The isotherm data demonstrated the Langmuir model fit for Zn(II), Mn(II) and Cu(II). The results showed that the chemical adsorption of single molecules was the main heavy metal removal mechanism. The maximum adsorption capacities (mg·g^-1) were ranked as Cu(II) (134.88) > Mn(II) (109.10) > Zn(II) (108.10)) by the single-metal adsorption isotherms at 298 K. Moreover, characterization analysis was performed using Fourier transform infrared spectroscopy, the Brunauer-Emmett-Teller method, scanning electron microscopy with energy-dispersive X-ray spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The results revealed that ion exchange was likely crucial in Mn(II) and Zn(II) removal, while C-O, O-H and C = O possibly were key to Cu(II) removal by complexing or other reactions.

Improved phenol sequestration from aqueous solution using silver nanoparticle modified Palm Kernel Shell Activated Carbon

Modified Palm Kernel Shell Activated Carbon (PKSAC) using silver nanoparticle (Ag-NPs-PKSAC) was investigated on phenol uptake from aqueous solution. Effects of temperature (500–700 °C), time (90–120 min), and alkaline concentration (0.1–0.5 M) were studied on the yield and methylene blue numbers for the synthesis. Effects of initial concentration (100–200 mg/L), agitation (150–250 rpm), contact time (30–120 min), and adsorbent dosage (0.15–0.25 g) were studied in a batch experiment on percentage removal of phenol. The PKS, char, PKSAC and Ag-NPs-PKSAC were characterized using BET, FTIR, SEM, and proximate analyses. The synthesis of PKSAC was optimum at 608 °C, 0.5 M KOH, and carbonization holding time of 60 min. The optimum phenol uptake was 85.64, 90.29 and 91.70% for PKSAC, Ag-NPs-PKSAC, and commercial adsorbent, respectively. The adsorption mechanism of phenol followed the Langmuir isotherm and best described as physio-sorption with pseudo-second-order kinetics. Phenol exhibits high affinity (ΔS° = 0.0079 kJ/mol K) for Ag-NPs-PKSAC with favorable adsorption (ΔG° = -1.551 kJ/mol) at high temperature due to endothermic (ΔH° = 1.072 kJ/mol) nature of the system. The result obtained in this study compared favorably with the literature.

Surface modification of biomaterials based on cocoa shell with improved nitrate and Cr(vi) removal

The present work addresses the development of simple, low-cost and eco-friendly cocoa-shell-based materials for efficient removal of heavy metal hexavalent chromium (Cr(vi)), and toxic nitrate (NO3 -) from aqueous solution. A conventional treatment process was used to purify cocoa shell (CS) into an adsorbent, followed by chemical grafting of dendrimers to promote its surface properties for nitrate and Cr(vi) removal. The morphology, surface charge, structure and stability of the new adsorbent were investigated by scanning electron microscopy, Fourier transform infrared and UV-visible spectroscopies, zeta potential, X-ray photoelectron spectrometry, and differential scanning calorimetry. The successful chemical grafting of the dendrimer (polyethyleneimine, PEI) onto purified CS was confirmed. CS-T-PEI-P proved to be a very efficient candidate for the removal of nitrate and chromium(vi). Removal of the two pollutants at different initial concentrations and pH values was studied and discussed. Sorption of chromium and nitrate was found to obey 2nd-order kinetics and a Freundlich-type isotherm, affording an uptake adsorption of 16.92 mg g-1 for NO3 - and 24.78 mg g-1 for Cr(vi). These results open promising prospects for its potential applications as a low cost catalyst in wastewater treatment.

Comparison study on the ammonium adsorption of the biochars derived from different kinds of fruit peel

Application of biochars to remove inorganic nitrogen (NH₄⁺, NO₂^-, NH₃, NO, NO₂, N₂O) from wastewater and agricultural fields has gained a significant interest. This study aims to investigate the relationship between ammonium sorption and physicochemical properties of biochars derived from different kinds of fruit peel. Biochars from three species of fruit peel (orange, pineapple and pitaya) were prepared at 300, 400, 500 and 600 °C with the residence time of 2 h and 4 h. Their characteristics and sorption for ammonium was evaluated. The results show a clear effect of pyrolysis conditions on physicochemical properties of biochars, including elemental composition, functional groups and pH. The maximum NH₄⁺ adsorption capacities were associated with biochars of orange peel (4.71 mg/g) and pineapple peel (5.60 mg/g) produced at 300 °C for 2 h. The maximum NH₄⁺ adsorption capacity of the pitaya peel biochar produced at 400 °C for 2 h was 2.65 mg/g. For all feedstocks, biochars produced at low temperatures showed better NH₄⁺ adsorption capacity. It was found that biochars had better adsorption efficiency on ammonium at a pH of 9. Adsorption kinetics of ammonium on biochars followed the pseudo-second-order kinetic model while Langmuir isotherm model could well simulate the adsorption behavior of ammonium on biochars. The adsorption mechanism of ammonium on biochars predominantly involved surface complexation, cation exchange and electrostatic attraction. Conclusively, the fruit peel-derived biochars can be used as an alternative to conventional sorbents in water treatment.

Comparative Adsorptive Removal of Phosphate and Nitrate from Wastewater Using Biochar-MgAl LDH Nanocomposites: Coexisting Anions Effect and Mechanistic Studies

In this study, date-palm biochar MgAl-augmented double-layered hydroxide (biochar-MgAl-LDH) nanocomposite was synthesized, characterized, and used for enhancing the removal of phosphate and nitrate pollutants from wastewater. The biochar-MgAl-LDH had higher selectivity and adsorption affinity towards phosphate compared to nitrate. The adsorption kinetics of both anions were better explained by the pseudo-first-order model with a faster removal rate to attain equilibrium in a shorter time, especially at lower initial phosphate-nitrate concentration. The maximum monolayer adsorption capacities of phosphate and nitrate by the non-linear Langmuir model were 177.97 mg/g and 28.06 mg/g, respectively. The coexistence of anions (Cl-, SO42-, NO3-, CO32- and HCO3-) negligibly affected the removal of phosphate due to its stronger bond on the nano-composites, while the presence of Cl- and PO43- reduced the nitrate removal attributed to the ions' participation in the active adsorption sites on the surface of biochar-MgAl-LDH. The excellent adsorptive performance is the main synergetic influence of the MgAl-LDH incorporation into the biochar. The regeneration tests confirmed that the biochar-MgAl composite can be restored effortlessly and has the prospective to be reused after several subsequent adsorption-desorption cycles. The biochar-LDH further demonstrated capabilities for higher removal of phosphate and nitrate from real wastewater.

Tuning tetracycline removal from aqueous solution onto activated 2:1 layered clay mineral: Characterization, sorption and mechanistic studies

Water pollution due to emerging contaminants (especially pharmaceuticals) is a major environmental threat which results in the development of antibiotic-resistant bacteria/resistance genes in the aquatic environment. Therefore, robust and cost-effective methods are required to address this problem. In this study, thermal activation was opted for the modification of natural bentonite clay (BC) and utilized to investigate the adsorptive removal of tetracycline (TC) from aqueous solution. The physicochemical surface properties of the raw and modified bentonite samples were also investigated. The BET analysis revealed that the thermally activated bentonite (TB) has better properties than BC. The surface area of TB was found to be more than two-fold higher compared to that of BC. The FTIR spectra exhibited the existence of AlOH, SiO and SiOSi functional groups in the samples, confirming the presence of hydrated aluminosilicate in the clay. The effects of various operating parameters were analyzed via optimization studies. The maximum monolayer adsorption capacity estimated by Langmuir model was found to be 156.7 and 388.1 mg g^-1 for BC and TB, respectively. Furthermore, fixed-bed column studies were performed to get insights into the adsorption behavior of TB in a dynamic system. The mechanism of TC adsorption by TB was successfully explored.

A Review of Non-Soil Biochar Applications

Biochar is the solid residue that is recovered after the thermal cracking of biomasses in an oxygen-free atmosphere. Biochar has been used for many years as a soil amendment and in general soil applications. Nonetheless, biochar is far more than a mere soil amendment. In this review, we report all the non-soil applications of biochar including environmental remediation, energy storage, composites, and catalyst production. We provide a general overview of the recent uses of biochar in material science, thus presenting this cheap and waste-derived material as a high value-added and carbonaceous source.

Facile hydrothermal synthesis of novel Fe-Cu layered double hydroxide/biochar nanocomposite with enhanced sonocatalytic activity for degradation of cefazolin sodium

This study reports the successful synthesis of Fe-Cu layered double hydroxide (Fe-Cu-LDH) /biochar (BC) nanocomposite by a hydrothermal method. The sonocatalytic performance of Fe-Cu-LDH/BC nanocomposite was investigated for the degradation of cefazolin sodium (CFZ), as a model emerging contaminant, from the solution. The physico-chemical properties of the synthesized samples were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive x-ray spectroscopy (EDX), Brunauer-Emmett-Teller (BET), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FT-IR), and UV-Vis diffuse reflectance spectroscopy (DRS) analyses. The best sonocatalytic efficiency of 97.6% was achieved by using 1.0 g/L sonocatalyst, 0.1 mM CFZ, and an ultrasonic power of 300 W at pH = 6.5 (natural) within 80 min. Additionally, the effects of the addition of various oxidants, dissolved gases, and organic and inorganic scavengers on the degradation of CFZ were studied. Moreover, the possible sonocatalytic mechanism of the sonochemical degradation of CFZ in the presence of Fe-Cu-LDH/BC sonocatalyst was proposed based on the results of GC-MS analysis. The mineralization of CFZ solution was evaluated using COD and IC analyses. Finally, the reusability test of Fe-Cu-LDH/BC nanocomposite in the CFZ degradation revealed that almost 9% drop occurred after five successive cycles.

Enhanced interlayer trapping of Pb(II) ions within kaolinite layers: intercalation, characterization, and sorption studies

Lead (Pb(II)) pollution in water poses a serious threat to human health in many parts of the world. In the past decades, research has been aimed at developing efficient and cost-effective methods to address the problem. In this study, dimethyl sulfoxide (DMSO) and potassium acetate (K-Ac) intercalated kaolinite complexes were synthesized and subsequently utilized for Pb(II) removal from water. The intercalation of kaolinite with DMSO was found to be useful for expanding the interlayer space of the clay mineral from 0.72 to 1.12 nm. Kaolinite intercalation with K-Ac (KDK) increased the interlayer space from 1.12 to 1.43 nm. The surface area of KDK was found to be more than threefold higher as compared to natural kaolinite (NK). Batch experimental results revealed that the maximum Pb(II) uptake capacity of KDK was 46.45 mg g^-1 which was higher than the capacity of NK (15.52 mg g^-1). Reusability studies showed that KDK could be reused for 5 cycles without substantially losing its adsorption capacity. Furthermore, fixed-bed column tests confirmed the suitability of KDK in continuous mode for Pb(II) removal. Successful application of intercalated kaolinite for Pb(II) adsorption in batch and column modes suggests its application in water treatment (especially removal of divalent metals).

Acidic surface functional groups control chemisorption of ammonium onto carbon materials in aqueous media

Elucidation of mechanistic insight into the interaction of carbon materials' physicochemical surface properties and ammonium (NH₄⁺) adsorption in aqueous media was made by conducting a systematic study using a wide range of carbon materials. Three types of biochars (rice husk, poultry litter, and enhanced poultry litter) and activated carbons (fresh and aged coconut shell-based and charcoal-based) were used for investigating the NH₄⁺ adsorption mechanism. Poultry litter biochar, with lowest surface area (3 m² g^-1) and largest pore diameter (29 nm), showed the highest NH₄⁺ adsorption capacity (0.34 mg NH₄⁺g^-1), while charcoal-based activated carbon, with the highest surface area (1133 m² g^-1) and small pore diameter (6 nm), had the least NH₄⁺ adsorption capacity (0.09 mg NH₄⁺g^-1). The value of Freundlich isotherm constant 'n' was >1 for all tested carbon materials indicating chemisorption as the dominant sorption mechanism. Aging of the carbon surface resulted in 30% increase in NH₄⁺ retention. Surface chemical properties that most influenced NH₄⁺ chemisorption on to carbon materials were found to be acidic surface functional groups (ASFGs), elemental composition, ash content, and pH. The optimal conditions for NH₄⁺ adsorption, regardless of type and source of carbon materials, were solution pH of 8, a high amount of ash content, and carboxyl, carbonyl, and phenolic functional groups. Evaluation of CEC and ASFGs indicated that CEC and ASFGs are not equivalent terms. Through this study, conducted on carbon adsorbents derived from different sources, with different surface physical and chemical properties, we established that ASFGs, and not CEC, play a critical role in ammonium chemisorption on carbon materials. The study showed that low cost and eco-friendly biochars, with optimal surface chemistry, can replace expensive activated carbons for NH₄⁺ remediation in aqueous media.

Enhanced removal of NO3-N from water using Fe-Al modified biochar: behavior and mechanism

To remove NO₃-N from water, coconut shell biochar (CSB) was modified by a solution of FeCl₃, a solution of AlCl₃ and a mixture solution of FeCl₃ and AlCl₃ respectively. The obtained modified biochar with the best effect of NO₃-N adsorption was screened out to explore the adsorption behavior and mechanism of NO₃-N removal by batch experiments and kinetics and thermodynamics and correlated characterization. The results indicated that the mixture solution of FeCl₃- and AlCl₃- modified CSB (Fe-Al/CSB) showed the best adsorption performance for NO₃-N removal. Iron and aluminum elements existed on the surface of Fe-Al/CSB in the form of FeOOH, Fe₂O₃, Fe²⁺, and Al₂O₃ respectively. The adsorption process could reach equilibrium in 20 min. An acidic condition was favorable for NO₃-N adsorption. The presence of coexisting anions was not conducive for NO₃-N adsorption. The quasi-second-order model and Freundlich model could be well fitted in the adsorption process. The maximum adsorption capacity of Fe-Al/CSB fitted by the Langmuir model could reach 34.20 mg/g. The adsorption of NO₃-N by Fe-Al/CSB was an endothermic and spontaneous process. Ligand exchange and chemical redox reaction were the NO₃-N adsorption mechanisms which led to NO₃-N adsorption by Fe-Al/CSB.

Removal of NO3-N in alkaline rare earth industry effluent using modified coconut shell biochar

Coconut shell biochar (CSB) was selected as raw material to obtain two kinds of modified biochars by pickling and iron modification. The pickling coconut shell biochar (PCSB) and pickling-iron modified coconut shell biochar (PICSB) were used as adsorbents to remove NO₃-N in alkaline rare earth industry effluent. The results showed that pickling smoothed the surface of CSB, and α-FeOOH was formed on the surface of PCSB because of FeCl₃ solution modification. Suitable adsorbent dosages of PCSB and PICSB were both 2.0 g/L. The NO₃-N adsorption process by PCSB and PICSB both reached equilibrium at 30 min. The quasi-first-order kinetic model shows good fit to the NO₃-N adsorption by PCSB. Whereas, the quasi-second-order kinetic model is more suitable for PICSB adsorbing NO₃-N. The adsorption mechanisms of PICSB for NO₃-N removal were ligand exchange and electrostatic attraction, and that of PCSB for NO₃-N removal was electrostatic attraction. The NO₃-N adsorption amounts of PCSB and PICSB decreased with increasing adsorption temperature and pH. The maximum NO₃-N adsorption amounts of PCSB and PICSB were 15.14 mg/L and 10.75 mg/L respectively with adsorbent dosage of 2.0 g/L, adsorption time of 30 min, adsorption temperature of 25 ± 1 °C, and initial solution pH of 2.01.

Potential of Punica granatum biochar to adsorb Cu(II) in soil

Biochar as a promising adsorbent to remove heavy metals has attracted much attention globally. One of the potential adsorbents is biochar derived from punica granatum peels, a growing but often wasted resource in tropical countries. However, the immobilization capacity of punica granatum peel biochar is not known. This study investigated the physicochemical properties of punica granatum peel boichars pyrolyzed at 300 °C and 600 °C (referred as BC300 and BC600), and the efficiency and mechanisms of Cu(II) adsorption of five types of material treatments: BC300, BC600, soil only, and soils with biochar amendment BC300 and BC600, respectively, at the rate of 1% of the soil by weight. The results show that BC300 had higher yield, volatile matter content and organic carbon content, and larger pore diameter, but less ash content, surface area, pH, and cation exchange capacity than BC600. The Cu(II) adsorption capacity onto biochars and soils with biochar were greatly influenced by initial ion concentration and contact time. The Cu(II) adsorption capacity of biochar, independent of pyrolysis temperature, was around 52 mg g⁻¹. The adsorption capacity of the soil amended with biochar nearly doubled (29.85 mg g⁻¹) compared to that of the original soil (14.99 mg g⁻¹), indicating superb synergetic adsorption capacity of the biochar-amended soils. The adsorption isotherms showed monolayer adsorption of Cu(II) on biochar, and co-existence of monolayer and multilayer adsorption in soils with or without biochar amendment. Results also suggest that the adsorption process is spontaneous and endothermic, and the rate-limiting phase of the sorption process is primarily chemical. This study demonstrates punica granatum peel biochar has a great potential as an adsorbent for Cu(II) removal in soil.

Adsorption of Nitrate by a Novel Polyacrylic Anion Exchange Resin from Water with Dissolved Organic Matters: Batch and Column Study

A novel anion exchange resin AEE-3 was synthesized by N-alkylation of a weakly basic polyacrylic anion exchanger D311 with 1-bromopropane to effectively remove nitrate (NO3−-N) from aqueous solution. The related finding revealed that its adsorption isotherm obeyed the Langmuir model well, and the second-order model was more validated for the NO3−-N adsorption kinetics study. Compared to commercially-available polystyrene-based nitrate specialty resin Purolite A 520E (A520E), AEE-3 resin has a higher adsorbed amount and better regeneration performance toward NO3−-N in the existence of dissolved organic matter (DOM) using static and dynamic methods. Notably, a real secondary treated wastewater (STWW) obtained from a local municipal wastewater treatment plant was also assessed for NO3−-N removal in fixed-bed columns. Observations from this study indicated that AEE-3 could effectively remove NO3−-N from contaminated surface water.