Phosphorus sorption capacity of biochars varies with biochar type and salinity level

A portable stir-disc solid phase extraction using biochar/sodium alginate mixed matrix membrane as absorbent for bisphenols enrichment in water samples

Recently, we designed a novel portable stir-disc SPE device. Biochar/sodium alginate (SA) mixed matrix membrane (MMM) was introduced as stir-disc SPE adsorbents for the first time. The stir-disc SPE device efficiently and conveniently extracted bisphenol contaminants in water samples. The biochar/SA MMM exhibited satisfactory adsorption properties and excellent reusability. The established pretreatment method was then successfully applied to extract five traces of BPs in water samples. The targets were sensitively detected by a high-performance liquid chromatography/fluorescence detector (HPLC-FLD). The factors including exaction time, elution time, type and volume of elution solvent, and sample solution pH were thoroughly optimized. The methodology validation indicated that the limits of detection for the BPs ranged from 0.06 to 0.17 ng·mL-1. The correlation coefficient (R2) of linearity was 0.9959-0.9994. Satisfactorily, the recoveries of five BPs ranged from 71% to 108%, and the RSD was less than 13.3%. The proposed method was effectively applied to analyze BPs in tap water, drinking water, and river water samples. The results of recycling experiments revealed that the biochar/SA MMM had excellent reusability for analyzing BPs in water samples. Therefore, this study offered a new perspective on sample treatment.

Improving the adsorption properties of low surface area hardwood biochar for the removal of Fe+ and PO₄3- from aqueous solution

Biochar produced from wood residues may provide a new method and material for managing the environment, particularly in terms of carbon sequestration and contaminant remediation. Additionally, biochar produced from wood residues is free of chemical fertilizers, likewise in rice straw, wheat straw, corn straw, etc. This study investigated the removal of iron from aqueous solutions by a novel low-cost and eco-friendly biochar made from hardwood trees and modified by adding MgCl2 for effective phosphate removal. Optimal adsorption conditions were determined through studies of adsorption time, pH, and adsorbent dosage. Batch equilibrium isotherm and kinetic experiments and pre/post-adsorption characterizations using FESEM-EDS, XRD, and FTIR suggested that the presence of carboxyl group elements and colloidal and nano-sized MgO (periclase) particles on the biochar surface were the main adsorption sites for aqueous iron and phosphate respectively. In this study, the HW and MgO-HW biochar showed excellent Dubinin-Radushkevich isotherm (D-R) maximum adsorption capacities of 289.45 and 828.82 mg/g for iron and phosphate. The kinetic study for iron and phosphate adsorption was described well by pseudo second-order model and pseudo second-order model respectively. The HW biochar and the prepared MgO-HW biochar exhibited commendable iron adsorption (98.25%) performance at 10 pH units and phosphate (96.22%) at pH 6 respectively. Thus, this research reveals a waste-to-wealth strategy by converting hardwood waste into mineral-biomass biochar with excellent Fe and P adsorption capabilities and environmental adaptability.

Effect of carbonaceous materials on phosphorus removal in flow-through packed column systems

Phosphorus (P) overloading in aquatic environments has long-been recognized as the leading cause of water quality deterioration, harmful algal bloom, and eutrophication. This study investigated P removal performance by five cost-effective carbonaceous materials (CMs) in flow-through packed column systems. These CMs include biochars pyrolyzed from feedstocks of Eucalyptus (E-biochar) and Douglas fir (D-biochar), commercial biochar (C-biochar), iron oxide-coated biochar (Fe-biochar), and commercial activated carbon (AC). The physicochemical properties of CMs, such as specific surface area (SSA), pore volume, pore diameter, elemental composition, and surface charge, were characterized. The packed column experimental results showed that P removal performance followed the order: E-biochar < D-biochar < C-biochar < Fe-biochar < AC. Specifically, the sorption capacity of 1 mg/L of P in packed columns was 0.0036 mg P/g E-biochar, 0.0111 mg P/g D-biochar, 0.0369 mg P/g D-biochar, 0.077 mg P/g Fe-biochar, and 0.088 mg P/g AC, respectively. The largest SSA (1012 m2/g) and pore volume (0.57 cm3/g) of AC accounted for the most outstanding P removal efficiency mainly by physical sorption, while electrostatic interaction explained the high P removal by Fe-biochar (SSA as low as 32.4 m2/g). Our findings provide direct practical implications for effectively removing P in water by cost-effective CMs.

Biochar-derived dissolved and particulate matter effects on the phytotoxicity of polyvinyl chloride nanoplastics

Nanoplastics in environments are potentially detrimental to plant growth. Appropriate doses of biochar can alleviate the phytotoxicity of nanoplastics under hydroponic conditions. However, the specific mechanisms remain unknown. In this study, the effects of biochar-derived dissolved matter (BCDM) and biochar-derived particulate matter (BCPM) on the phytotoxicity of polyvinyl chloride (PVC) nanoplastics were investigated and the underlying influencing mechanisms were elucidated. The results showed that PVC nanoplastics can be adsorbed and taken up by lettuce roots, inducing oxidative damage to lettuce shoots and roots and reducing their fresh weight. BCDM can promote the aggregation and sedimentation of PVC nanoplastics, and BCPM can adsorb PVC nanoplastics and cause barrier effect, which will reduce the exposure dose of PVC nanoplastics. Furthermore, nutrients in BCDM can promote lettuce growth. As a result, the presence of both BCDM and BCPM significantly mitigated the oxidative stress of lettuce shoots and roots as demonstrated by the decrease in hydrogen peroxide and malondialdehyde levels (p < 0.05). Meanwhile, lettuce biomass was significantly increased after addition of BCDM and BCPM compared to the single PVC treatment group (p < 0.05). This study provides a theoretical basis for finding solutions to alleviate the phytotoxicity of nanoplastics.

Treatment of faecal sludge and sewage effluent by pinewood biochar to reduce wastewater bacteria and inorganic contaminants leaching

Biochar is a valuable treatment option for faecal sludge management (FSM). However, the sanitation application rates of biochar in FSM are not well established. There is also a gap in knowledge about the effect of actual raw sewage effluent and sludge on organic and inorganic contaminants migration of biochar treated soil. This study investigated the concentration and migration rates of N, P, E. coli and faecal coliform bacteria through different soil-bed biochar column treatments leached with raw faecal sludge and sewage effluent. Forty-four soil-bed leaching columns with pinewood biochar rates at 5, 10 and 20 t/ha were set at the Bloemspruit wastewater plant, South Africa. The pinewood biochar used had a pH of 10.21, total C composition of 92%, surface area of 517 m²/g, and a pore size of 1.7 nm. It was found that the 20 t biochar per ha treatment with faecal sludge increased water retention (flows of 33 mm/h. at 0 t/ha compared to 0.8 mm/h. at 20 t/ha) and leachates purification. High detections were observed for faecal coliforms and E.coli above 4331 CFU/100 mL from the effluent and faecal sludge in soils without biochar. Detection of E.coli at 20 t/ha decreased to 1 CFU/100 mL while the faecal coliforms still had counts above 10 CFU/ 100 mL. The results showed a decreasing rate of nitrates, phosphates, zinc and copper with an increasing biochar application rate. Pinewood biochar showed significant removal efficiencies of bacteria (between 89 and 98%) and nitrates and phosphates (between 68 and 98%). Significant differences were seen at P < 0.05 between the means of the treatments with and without biochar. The results from the study show that pinewood biochar applied at rates between 5 and 20 t/ha has a high organic and inorganic contaminants reduction potential for FSM.

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 PO4 3--P from urine. The effects of dosage, adsorption time, and urine concentration on the adsorption of NH4 +-N and PO4 3--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 PO4 3--P. Both the NH4 +-N and PO4 3--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 PO4 3--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 PO4 3--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 PO4 3--P from urine as a fertilizer.

Enhanced adsorption of phosphorus in soil by lanthanum-modified biochar: improving phosphorus retention and storage capacity

Use of soil adsorbent is an effective method for the promotion of phosphorus adsorption capacity of soil, though most of the soil adsorbents have weak phosphorus retention ability. Herein, we compared the traditional gypsum (GP) and zeolite (ZP) adsorbents to explore the phosphorus retention ability of lanthanum modified walnut shell biochar (La-BC) in soil. The results showed that with the increase of exogenous phosphorus concentration, the adsorption amount of phosphorus by adsorbents in soil increased at first and then tended to be stable. The maximum adsorption capacity of soil to phosphorus is gypsum, lanthanum-modified biochar > zeolite, and the addition of lanthanum-modified biochar can improve the adsorption capacity of soil to phosphorus, enhance the binding strength of soil and phosphorus, improve the ability of soil to store phosphorus, reducing phosphorus adsorption saturation, and is beneficial to control the leaching of soil phosphorus. FTIR and XRD analysis showed that the adsorption of phosphorus by each adsorbent in soil was mainly chemical precipitation. The response surface analysis showed that the adsorption performance of La-BC+S was the best when the concentration of exogenous phosphorus was 50.0 mg/L, pH was 6.47, and the reaction time was 436.98 min. This study provides a reference for soil adsorbents to hold phosphorus and reduce the risk of phosphorus leaching to avoid groundwater pollution.

Agricultural Waste-Based Biochar for Agronomic Applications

Agricultural activities face several challenges due to the intensive increase in population growth and environmental issues. It has been established that biochar can be assigned a useful role in agriculture. Its agronomic application has therefore received increasing attention recently. The literature shows different applications, e.g., biochar serves as a soil ameliorant to optimize soil structure and composition, and it increases the availability of nutrients and the water retention capacity in the soil. If the biochar is buried in the soil, it decomposes very slowly and thus serves as a long-term store of carbon. Limiting the availability of pesticides and heavy metals increases soil health. Biochar addition also affects soil microbiology and enzyme activity and contributes to the improvement of plant growth and crop production. Biochar can be used as a compost additive and animal feed and simultaneously provides a contribution to minimizing greenhouse gas emissions. Several parameters, including biochar origin, pyrolysis temperature, soil type when biochar is used as soil amendment, and application rate, control biochar’s efficiency in different agricultural applications. Thus, special care should be given when using a specific biochar for a specific application to prevent any negative effects on the agricultural environment.

Lipoic Acid Combined with Melatonin Mitigates Oxidative Stress and Promotes Root Formation and Growth in Salt-Stressed Canola Seedlings (Brassica napus L.)

Lipoic acid (LA) and melatonin (MT) are pleiotropic molecules participating in plant stress resistance by modulating cellular biochemical changes, ion homeostasis, and antioxidant enzyme activities. However, the combined role of these two molecules in counteracting the detrimental impacts of salinity stress is still unknown. In the present study, we determined the effects of exogenous LA (0.5 µM), MT (1 µM) and their combination (LA + MT) on growth performance and biomass accumulation, photosynthetic pigments, enzymatic and non-enzymatic antioxidant activities, and ions homeostatic in canola (Brassica napus L.) seedlings under salinity stress (0, 100 mM) for 40 days. The results indicate that exogenous application of LA + MT improved the phenotypic growth (by 25 to 45%), root thickness (by 68%), number of later lateral roots (by 52%), root viability (by 44%), and root length (by 50%) under salinity stress. Moreover, total soluble protein, chlorophyll pigments, the concentration of superoxide dismutase (SOD), catalase peroxidase (CAT), and ascorbic peroxidase (ASA) increased with the presence of salt concentration into the growth media and then decreased with the addition of LA + MT to saline solution. Leaf protein contents and the degradation of photosynthetic pigments were lower when LA + MT treatments were added into NaCl media. The proline and phenol contents decreased in the exogenous application of LA + MT treatments more than individual LA or MT treatments under the salinity stress. The incorporation of LA or MT or a combination of LA + MT to saline solution decreased salinity-induced malondialdehyde and electrolyte leakage. In conclusion, the alteration of metabolic pathways, redox modulation, and ions homeostasis in plant tissues by the combined LA and MT application are helpful towards the adaptation of Brassica napus L. seedlings in a saline environment. The results of this study provide, for the first time, conclusive evidence about the protective role of exogenous LA + MT in canola seedlings under salinity stress.

Modification of Hardwood Derived Biochar to Improve Phosphorus Adsorption

The excessive application of phosphorus in agricultural lands leads to serious environmental issues. Efficient application is beneficial from an economic and environmental perspectives. Biochar can be used as a carrier for slow release of phosphate. However, its adsorption capacity is limited. In this work, biochar was prepared at different pyrolysis temperatures (350–550 °C). The biochar prepared at 550 °C had the highest adsorption capacity and was selected for modification by magnesium impregnation. Magnesium modification enhanced the adsorption capacity by 34% to a theoretical max adsorption capacity of 463.5 mg·g−1. The adsorbed phosphate can be desorbed. The desorption was bi-phasic with fast- and slow-release fractions. The distribution of the phosphate fractions was pH dependent with slow release being most prominent in neutral conditions. Mg modified biochar can be used to recover phosphate and then used as a carrier for slow release of phosphate. The bi-phasic desorption behaviour is useful as the fast release fraction can provide the immediate phosphate needed during plant establishment, while the slow-release fraction maintains steady supply over extended periods.

Effect of three different types of biochars on eco-physiological response of important agroforestry tree species under salt stress

Soil reclamation through afforestation along with soil amendments is one of the most suitable practices to combat soil salinity while the use of biochar may have potential to ameliorate salt-affected soils. This study was designed to check effects of different biochars on the physico-chemical properties of soil and characteristics of three important agroforestry trees species: Eucalyptus camaldulensis, Vachellia nilotica and Dalbergia sissoo, in saline soils. Farmyard manure biochar (FYMB), sugarcane bagasse biochar (SCB), woodchips biochar (WCB) were applied (6% w/w) to check their effects on plants under saline conditions. Results revealed that FYMB was the best for promoting all growth and physiological parameters of three tree species while E. camaldulensis was the best suited species. Different types of biochars influenced the growth of agroforestry species differently as SCB showed better results for D. sissoo as compared to WCB but for V. nilotica and WCB was more effective than SCB. Trend of growth and other physiological attributes for E. camaldulensis and V. nilotica was FYMB > WCB > SCB > control whereas D. sissoo showed trend as FYMB > SCB > WCB > control. Biochar was helpful in improving physicochemical characteristics of saline soils by lowering values of soil EC and SAR but type of biochar has a differential effect on tree growth.Novelty statement: Biochar may be a potential source for the amelioration of salt affected soils while less is known about the effects of different types of biochars on the soil and eco-physiological response of important agroforestry trees species in saline soils. In this study, although all types of biochar ameliorated the soil conditions and enhanced the plant growth, but farmyard manure biochar was the most efficient treatment among three types of used biochars.

Phosphorus Removal from Wastewater: The Potential Use of Biochar and the Key Controlling Factors

In recent years, a large volume of literature has been published regarding the removal of phosphorus (P) from wastewater. Various sorbing materials, such as metal oxides and hydroxides, carbonates and hydroxides of calcium (Ca) and magnesium (Mg), hydrotalcite, activated carbon, anion exchange resins, industrial solid wastes and organic solid wastes, have been suggested for P removal. Many of these sorbents are expensive and/or may cause some environmental problems. In contrast, biochar, as an economical and environmentally friendly sorbing material, has received much attention in recent years and has been used as a novel sorbent for the removal of different organic and inorganic pollutants. Biochar is a type of sustainable carbonaceous material that is produced from the thermal treatment of agricultural organic residues and other organic waste streams under oxygen free conditions. This paper reviews the potential use of biochar and the key controlling factors affecting P removal from wastewater. The ability of biochar to remove P from wastewater depends on its physical and chemical properties. Some of the most important physicochemical properties of biochar (structural characteristics, electrical conductivity (EC), mineral composition, pH, zeta potential, cation exchange capacity (CEC) and anion exchange capacity (AEC)) are affected by the feedstock type as well as temperature of pyrolysis and the P sorption capacity is highly dependent on these properties. The P removal is also affected by the water matrix chemistry, such as the presence of competing ions and bulk pH conditions. Finally, several recommendations for future research have been proposed to facilitate and enhance the environmental efficiency of biochar application.

Biochar technology in wastewater treatment: A critical review

Biochar is a promising agent for wastewater treatment, soil remediation, and gas storage and separation. This review summarizes recent research development on biochar production and applications with a focus on the application of biochar technology in wastewater treatment. Different technologies for biochar production, with an emphasis on pre-treatment of feedstock and post treatment, are succinctly summarized. Biochar has been extensively used as an adsorbent to remove toxic metals, organic pollutants, and nutrients from wastewater. Compared to pristine biochar, engineered/designer biochar generally has larger surface area, stronger adsorption capacity, or more abundant surface functional groups (SFG), which represents a new type of carbon material with great application prospects in various wastewater treatments. As the first of its kind, this critical review emphasizes the promising prospects of biochar technology in the treatment of various wastewater including industrial wastewater (dye, battery manufacture, and dairy wastewater), municipal wastewater, agricultural wastewater, and stormwater. Future research on engineered/designer biochar production and its field-scale application is discussed. Based on the review, it can be concluded that biochar technology represents a new, cost effective, and environmentally-friendly solution for the treatment of wastewater.

Spectroscopic studies on the phosphorus adsorption in salt-affected soils with or without nano-biochar additions

Biochar amendment may be an effective solution of maintaining phosphorus (P) and sustaining agricultural production in salt affected soils. However, the behavior of P adsorption in salt-affected soils with nano-biochar (nB) amendment is unclear. Batch adsorption experiments were conducted to investigate the impacts of different levels of soil salinity amended with nB at rates of 0, 0.10%, 0.20%, and 0.50% (w/w) on the P adsorption isotherm and also, mechanisms of P adsorption by using spectroscopic analysis. The results showed that P adsorption increased with increasing soil salinity with or without nB addition. Under level of 120 mg P L^-1, adsorption capacity of P increased from 992.8 mg kg^-1 for high saline soil (S5) to 1144.0 mg kg^-1 after treated with 0.20% nB. The results of P adsorption were agreed with Langmuir and Freundlich isotherm models. Fourier transform infrared analysis (FTIR) of nB showed that the surface of nB decorated with oxygenated functional groups which play an important role in the adsorption of P anions. Analyzes of FTIR and XRD indicated that the main adsorption mechanism for P adsorption on nB in salt affected soils was surface precipitation. Our findings suggest that the nano-biochar amendment in salt affected soils can be a promising enhancer for P adsorption.

Almond and walnut shell-derived biochars affect sorption-desorption, fractionation, and release of phosphorus in two different soils

Effective soil phosphorus (P) management requires higher level of knowledge concerning its sorption-desorption, fractionation, and release, as well as its interactions with soil amendments including biochar (BC). The purpose of this research was to investigate the influence of two different BCs, derived from almond and walnut shell, on P sorption-desorption and its redistribution among the geochemical fractions in two different soils. The BCs were applied to the soils in four doses (0, 2.5, 5, and 10% w/w) and the mixtures were incubated for one month. Phosphorus sorption increased due to the addition of BCs. Phosphorus sorption data fitted well the Freundlich isotherm and were simulated by the PHREEQC software. Biochar addition increased total P and the added P was mainly distributed in the exchangeable, Fe/Al-P and the residual fractions. Also, BC addition resulted in an increase in the water-soluble-, mobile-, and Olsen-P, making P more available for plant uptake. The kinetics data were well described by the simple Elovich, pseudo-second-order, and intra-particle diffusion equations. Walnut BC-added soils had higher P sorption capacity than those added with the almond BC. The results suggest that BC binds soil P and releases it gradually back into solution, making it thus available to plants; this renders the studied BCs promising materials for protecting P from being lost out of soil. Future research must be conducted over longer-term experiments that would study P dynamics in BC-added soils under real field conditions.

Achievements of biochar application for enhanced anaerobic digestion: A review

Anaerobic digestion (AD) and pyrolysis are two promising technologies used worldwide for waste biomass treatment. Interests on intensification techniques of AD has been increasing to obtain sufficient and sustainable methane production with stable digester performance. For instance, considerable attention has been devoted to the coupling of AD with biochar, which is produced by biomass thermochemical conversion. This manuscript presents a comprehensive review about recent achievements in enhancing AD efficiency with the utilization of biochar. The key roles of biochar include enhancing and equilibrating hydrolysis, acidogenesis-acetogenesis, and methanogenesis, as well as alleviating inhibitor stress were summarized. Biochar can promote biomethane process mainly by serving as a provision for bioelectrical connections between fermentative bacteria and methanogens, a support for microbial colonies, and a reinforcer for buffer capacity. Through an overview of the early applications, this paper aims to pinpoint the potential mechanism and future explorative directions of biochar enhancing AD performance.

Hydrogel chitosan sorbent application for nutrient removal from soilless plant cultivation wastewater

In this study, we determined the effectiveness of removal of nutrients (nitrates and orthophosphates) from greenhouse wastewaters (GW) using non-cross-linked chitosan (CHs) and chitosan cross-linked with epichlorohydrin (CHs-ECH) in the form of hydrogel beads. GW used in the study had the following parameters: N-NO₃ 621.1 mg/L, P-PO₄ 60.8 mg/L, SO₄^2- 605.0 mg/L, Cl^- 0.9 mg/L, Ca²⁺ 545.0 mg/L, Mg²⁺ 178.0 mg/L, K⁺ 482.0 mg/L, hardness 113° dH, and pH 6.2. The scope of the study included determination of the effect of pH on wastewater composition and effectiveness of nutrient sorption, analyses of nutrient sorption kinetics, and analyses of the effect of sorbent dose on percentage removal of nutrients from GW. CHs-ECH was able to sorb 79.4% of P-PO₄ and 76.7% of N-NO₃ from GW, whereas CHs to remove 92.8% of P-PO₄ and 53.2% of N-NO₃.