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The present study investigates the impact of biomass origin on the properties of biochar and its interaction with different treatment conditions, CO2 adsorption, and regeneration ability. The bioch...

The coadsorption of Hg⁰ and SO₃ on pure and Cu/Mn doped CeO₂(110) surfaces were investigated using the Density Functional Theory (DFT) method. A p (2 × 2) supercell periodic slab model with seven atomic layers was constructed to represent the CeO₂(110) surface. The results indicated that Hg⁰ physically adsorbed on the CeO₂(110) surface, while Hg⁰ chemically adsorbed on the Cu/Mn doped CeO₂(110) surface, which agree well with the experimental results that Cu and Mn doped CeO₂ greatly improved the Hg⁰ adsorption capacity of the adsorbent. The calculated results suggested that SO₃ more easily adsorbs on the above three surfaces than Hg⁰ due to the higher adsorption energy. The adsorption configurations and electronic structures indicated SO₃ reacted with O atoms of the surface to form SO₄²– species. Hence, SO₃ inhibits Hg⁰ adsorption on the CeO₂(110) surface by competing with Hg⁰ for surface lattice oxygen. In addition, SO₃ decreased the activity of the surface O atoms, which directly caused the negative effect on Hg⁰ adsorption.

Biochar is a solid by-product of thermochemical conversion of biomass to bio-oil and syngas. It has a carbonaceous skeleton, a small amount of heteroatom functional groups, mineral matter, and water. Biochar’s unique physicochemical structures lead to many valuable properties of important technological applications, including its sorption capacity. Indeed, biochar’s wide range of applications include carbon sequestration, reduction in greenhouse gas emissions, waste management, renewable energy generation, soil amendment, and environmental remediation. Aside from these applications, new scientific insights and technological concepts have continued to emerge in the last decade. Consequently, a systematic update of current knowledge regarding the complex nature of biochar, the scientific and technological impacts, and operational costs of different activation strategies are highly desirable for transforming biochar applications into industrial scales. This communication presents a comprehensive review of physical activation/modification strategies and their effects on the physicochemical properties of biochar and its applications in environment-related fields. Physical activation applied to the activation of biochar is discussed under three different categories: I) gaseous modification by steam, carbon dioxide, air, or ozone; II) thermal modification by conventional heating and microwave irradiation; and III) recently developed modification methods using ultrasound waves, plasma, and electrochemical methods. The activation results are discussed in terms of different physicochemical properties of biochar, such as surface area; micropore, mesopore, and total pore volume; surface functionality; burn-off; ash content; organic compound content; polarity; and aromaticity index. Due to the rapid increase in the application of biochar as adsorbents, the synergistic and antagonistic effects of activation processes on the desired application are also covered.

The present study discusses a novel ultrasound promoted amination technique to functionalize graphene oxide (GO) for CO2 adsorption. Graphene oxide was synthesized following the modified Hummer’s method. The developed functionalization technique integrates the advantages of low-frequency ultrasonic physical activation with the chemical functionalization using tetraethylenepentamine (TEPA). Acoustic treatment exfoliates the clusters of graphene oxide and enhances the surface area for the subsequent amine functionalization and CO2 adsorption. Changes in textural properties, surface functionalities, thermal stability, and elemental compositions were examined before and after activation of graphene oxide. The characterization results revealed substantial increment of N content, from 0.08 in pristine to 4.84% in functionalized GO and the subsequent reduction in surface area from 289 to 198 m2/g in the functionalized GO, indicating attachment of TEPA to GO structure. CO2 adsorption experiments were conducted under diluted CO2 with the partial pressure of 0.10 atm. at 338 K and the results revealed that ultrasonic-TEPA activated GO possessed enhanced adsorption capacity of 1.2 mmol g−1 over pristine GO. While pristine GO could only achieve the maximum adsorption capacity of 0.3 mmol g−1 at 303 K. Besides, the sonochemically modified adsorbent showed stable cyclic adsorption-regeneration performance with only 1% reduction in adsorption capacity after 10 cycles. Finally, the effectiveness of the developed physicochemical activation technique was determined by comparing its adsorption capacity with the adsorbents found from literature.

The main objective of a series of our researches is to develop a novel acoustic-based method for activation of biochar. This study investigates the capability of biochar in adsorbing Ni(II) as a hazardous contaminant and aims at enhancing its adsorption capacity by the addition of extra nitrogen and most probably phosphorous and oxygen containing sites using an ultrasono-chemical modification mechanism. To reach this objective, biochar physically modified by low-frequency ultrasound waves (USB) was chemically treated by phosphoric acid (H3PO4) and then functionalized by urea (CO(NH2)2). Cavitation induced by ultrasound waves exfoliates and breaks apart the regular shape of graphitic oxide layers of biochar, cleans smooth surfaces, and increases the porosity and permeability of biochar’s carbonaceous structure. These phenomena synergistically combined with urea functionalization to attach the amine groups onto the biochar surface and remarkably increased the adsorption of Ni(II). It was found that the modified biochar could remove > 99% of 100 mg Ni(II)/L in only six hours, while the raw biochar removed only 73.5% of Ni(II) in twelve hours. It should be noted that physical treatment of biochar with ultrasound energy, which can be applied at room temperature for a very short duration, followed by chemical functionalization is an economical and efficient method of biochar modification compared with traditional methods, which are usually applied in a very severe temperature (>873 K) for a long duration. Such modified biochars can help protect human health from metal-ion corrosion of degrading piping in cities with aging infrastructure.

This study investigates the potential of cow dung, an animal manure, as a binder to enhance the physicochemical properties of the base pellet (a mixture of wheat straw and rice husk). In the first step, preliminary experiments were performed to select the best composition of wheat straw and rice husk for the base pellet. The selection was based on calorific value. Subsequently, the effect of operating parameters such as varying compositions of cow dung (0–100%), molasses concentration (0–100%) and drying time (12–48 h) was investigated. Thus, Central Composite Design using Response Surface Methodology was used to investigate the proximate analysis, calorific value, bulk density and durability of biomass pellets. The experimental results suggested that the addition of cow dung into the base pellet resulted in the increase of volatile matter, ash content, bulk density and durability of the base pellet. As a result, the maximum calorific value of 14.98 MJ/kg, moisture content of 3.37%, volatile matter of 45.49%, ash content of 31.38%, bulk density of 108990 kg/m3 and durability of 95% were obtained. However, optimization of operating parameters was performed to optimize the ash percentage. With the pellet composition of 8.5% (base pellet composition of 90% wheat straw and 10% rice husk), molasses concentration of 50% and drying time of 12 h, 52% reduction in ash content and 2.3% increase in calorific value were obtained at the cost of 38% reduction in the bulk density and insignificant reduction in durability of the produced pellet. Therefore, the use of waste material like cow dung as a binder can be considered as a sustainable approach to improve the physicochemical properties especially durability of biomass pellets. Thus, it can effectively be used to fulfill the energy and heating requirement of rural areas.

The present study examined the effect of pyrolysis temperature on the physicochemical properties of biochar, activation process and carbon capture. Two different categories of biochars were synthesized from herbaceous (miscanthus and switchgrass) or agro-industrial (corn stover and sugarcane bagasse) feedstock under four different pyrolysis temperatures- 500, 600, 700 and 800 oC. The synthesized biochars underwent sono-amination activation comprising low-frequency acoustic treatment followed by amine functionalization to prepare adsorbents for CO2 capture. As per the elemental analysis, the elevated pyrolysis temperature resulted in increased %C and %ash contents and reduced %N contents of biochar. The textural analysis exhibited almost 3-times enhancement of micro surface area and pore volume upon increasing the pyrolysis temperature from 500 to 700 oC, though further increase to 800 oC reduced the micro-porosity and the surface area. The intermediate temperatures of 600 and 700 oC revealed the highest interactions with ultrasound-amination, which significantly intensified CO2 adsorption. Accordingly, the CO2 capture capacity of sono-aminated biochars synthesized at 600 and 700 oC were almost 200% greater than that of raw biochars. There were 127-159% and 115-151% increases in adsorption capacity of biochars synthesized at 800 and 500 oC upon ultrasono-amine functionalization. Miscanthus biochar synthesized at 700 oC and treated sono-chemically demonstrated the highest adsorption ability of 2.89 mmol/g at 70 oC and 0.10 atm partial pressure, which is 211% higher than its pristine condition. The superior adsorption capacity of miscanthus (at 700 oC) can be attributed to its large surface area (324.35 m2/g), high carbon content (84%), and low ash content (4.9%), as well as its %N content after sono-amination that was twice that of raw char.

The present study discusses a novel biochar activation technique consisting of physical modification using low frequency ultrasound and chemical functionalization with individual amines and their b...

The objectives of a series of our researches are to determine the feasibility of applying ultrasonic pretreatment prior to biochar gasification. As per the initial results, the heating value (HV) of biochar significantly increased after acoustic treatment in water with dissolved CO2 (AIChE Journal, 2014;60:1054–1065). Accordingly, emphasis of the current work is placed on the parameters governing the HV of biochar in the early stage of the treatment. Switchgrass and miscanthus biochars were treated under different conditions. The reactant ratio, biochar:water:CO2, exhibited profound impacts on the synergism. The highest (but not yet systematically optimized) ratio of HV increase (or HV Gain, HG) to ultrasound energy supplied (ES) takes place when biochar-to-water ratio, or BC:W, equals 0.06 g/ml. The observed HG/ES is about 10, suggesting that the energy consumption is only a fraction of the acoustic energy supplied. Miscanthus biochar’s HV increases by up to 4.6% after treatment at 5% amplitude for 135 s (HG = 33 cal/g). For the same run, miscanthus biochar's H content increased by 42.7%. Changes in HV can be mediated by mineral leaching, C or H fixation, or O content loss. Mineral leaching is influenced by pH and CO2 concentration. CO2 and water are the sole contributors to C and H gains, respectively. CO2 concentration in the solution during the treatment is also affected by mass transfer limitations, ultrasound power, and design of the three-phase reactor. Increasing the BC:W ratio initially enhances the cavitation nuclei on the fluid/solid surface, and therefore sonolysis. The subsequent decrease in HV with increasing BC:W may be due to the limitation in ultrasound penetration and H supply from water. Carbon and hydrogen fixation may be connected to the formation of H2, CO, formic acid, formaldehyde, and associated radicals during sonolysis of aqueous CO2.

Generation of hydroxyl radicals (⋅OH) is the basis of advanced oxidation process (AOP). This study investigates the catalytic activity of microporous carbonaceous structure for in-situ generation of ⋅OH radicals. Biochar (BC) was selected as a representative of carbon materials with a graphitic structure. The work aims at assessing the impact of BC structure on the activation of H2O2, the reinforcement of the persistent free radicals (PFRs) in BC using heavy metal complexes, and the subsequent AOP. Accordingly, three different biochars (raw, chemically- and physiochemically-activated BCs) were used for adsorption of two metal ions (nickel and lead) and the degradation of phenol (100 mg/L) through AOP. The results demonstrated four outcomes: (1) The structure of carbon material, the identity and the quantity of the metal complexes in the structure play the key roles in the AOP process. (2) the quantity of PFRs on BC significantly increased (by 200%) with structural activation and metal loading. (3) Though the Pb-loaded BC contained a larger quantity of PFRs, Ni-loaded BC exhibited a higher catalytic activity. (4) The degradation efficiency values for phenol by modified biochar in the presence of H2O2 was 80.3%, while the removal efficiency was found to be 17% and 22% in the two control tests, with H2O2 (no BC) and with BC (no H2O2), respectively. Overall, the work proposes a new approach for dual applications of carbonaceous structures; adsorption of metal ions and treatment of organic contaminants through in-situ chemical oxidation (ISCO).

Renewable energy sources e.g. biofuels, are the focus of this century. Economically and environmental friendly production of such energies are the challenges that limit their usages. Microalgae is one of the most promising renewable feedstocks. However, economical production of microalgae lipid in large scales is conditioned by increasing the lipid content of potential strains without losing their growth rate or by enhancing both simultaneously. Major effort and advances in this area can be made through the environmental stresses. However, such stresses not only affect the lipid content and species growth (biomass productivity) but also lipid composition. This study provides a comprehensive review on lipid enhancement strategies through environmental stresses and the synergistic or antagonistic effects of those parameters on biomass productivity and the lipid composition. This study contains two main parts. In the first part, the cellular structure, taxonomic groups, lipid accumulation and lipid compositions of the most potential species for lipid production are investigated. In the second part, the effects of nitrogen deprivation, phosphorus deprivation, salinity stress, carbon source, metal ions, pH, temperature as the most important and applicable environmental parameters on lipid content, biomass productivity/growth rate and lipid composition are investigated.

A series of biochars were prepared from rice(RI), tobacco(TO), corn(CO), wheat(WH), millet(MI), and black bean straw(BB). These biochars were used to study the mechanism of elemental mercury(Hg0) adsorption by hydrochloric acid modified biochars. The biochars were modified by 1 M hydrochloric acid (HCl) and then used in a fixed-bed Hg0 adsorption experiment. As would be expected, the results indicated that HCl modification increased the Hg0 adsorption performance of the six biochars. After modification, the Hg0 adsorption efficiency of tobacco biochar increased from 8.2% to 100.0%, and the average Hg0 adsorption capacity of the biochars increased by 61 times. The acid modification dissolved the metal compounds in the biochar, reducing the metal content and increasing the average surface area of the biochar. The average surface area of the raw biochars increased from 29.9 to 110.1 m2/g after HCl modification. The extra surface area was mostly created in the micropores, leading to a significant increase in the amount of micropores. These micropores effectively adsorbed the Cl atoms, which acted as active sites for Hg0. In the adsorption process, Hg0 diffused into the interior of modified biochars via mesopores, and finally the adsorbed Cl in the micropores reacted with Hg0 to form HgCl2.

Biochar (BC) generated from thermal and hydrothermal cracking of biomass is a carbon-rich product with the microporous structure. The graphene-like structure of BC contains different chemical functional groups (e.g. phenolic, carboxylic, carbonylic, etc.), making it a very attractive tool for wastewater treatment, CO2 capture, toxic gas adsorption, soil amendment, supercapacitors, catalytic applications, etc. However, the carbonaceous and mineral structure of BC has a potential to accept more favorable functional groups and discard undesirable groups through different chemical processes. The current review aims at providing a comprehensive overview on different chemical modification mechanisms and exploring their effects on BC physicochemical properties, functionalities, and applications. To reach these objectives, the processes of oxidation (using either acidic or alkaline oxidizing agents), amination, sulfonation, metal oxide impregnation, and magnetization are investigated and compared. The nature of precursor materials, modification preparatory/conditions, and post-modification processes as the key factors which influence the final product properties are considered in detail; however, the focus is dedicated to the most common methods and those with technological importance.

This paper describes a two-stage biochar activation process for CO2 capture, which includes acoustic treatment and amination. Contrarily to traditional carbon activation at temperatures above 700 °C, both stages of the current process are conducted at or near room temperature. It is known that CO2 can be fixed on the edge carbons of polycyclic aromatics hydrocarbons (PAHs) through thermal and reductive photo-carboxylation. Our previous work on biochar suggested that carbon of CO2 could be chemically fixed on biochar through acoustic or photochemical treatment of biochar in water/CO2 systems under ambient conditions. Separately, the graphene oxide (GO) literature reveals that carboxylic acids, epoxy and hydroxyl groups on biochar surface often serve as the active sites for converting GO to a new family of chemicals; amines are commonly grafted on these groups in the functionalization. Biochar has graphite and graphitic oxide clusters that consist of the oxygen functional groups mentioned above. These oxygen functionalities can be utilized for CO2 adsorption when functionalized with amine. Thus, the present study focuses on maximizing the CO2 capture capacity by manipulating the physicochemical structure of a pinewood-derived biochar. In this two-stage process, 30 s sonication at ambient temperature was applied to physically activate biochar prior to functionalization. Low-frequency ultrasound irradiation exfoliates and breaks apart the irregular graphitic layers of biochar, and creates new/opens the blocked microspores, thus enhancing the biochar’s porosity and permeability that are the keys in functionalization and subsequent CO2 capture. The sono-modified biochar was then functionalized with tetraethylenepentamine (TEPA) in the presence of two activating agents. The changes in surface characteristics, functional groups, graphene-like structure, and functionalization using activating agents were examined in detail and the capacity of the final products in CO2 removal was tested. The experimental results revealed that CO2 capture capacity, from a flow containing 10 and 15 vol% CO2, was almost 7 and 9 times higher, respectively, for ultrasound-treated amine-activated biochar, compared to raw biochar. The optimum capacity was 2.79 mmol/g at 70 °C and 0.15 atm CO2 partial pressure. Cyclic adsorption and desorption tests revealed that the CO2 capture capacity decreased 44% after 15 cycles.

Biochar, known as a byproduct of biomass pyrolysis, was prepared from rice straw (R6), tobacco straw (T6), corn straw (C6), wheat straw (W6), millet straw (M6), and black bean straw (B6) in high purity nitrogen at 600 °C. Chlorine (Cl) non-thermal plasma was used to increase Cl active sites on biochar to promote the mercury removal efficiency. The physio-chemical properties of biochar were characterized by proximate analysis, ultimate analysis, BET, SEM, TGA, FTIR, and XPS. Modification by chlorine plasma increased the Hg0 removal efficiency of the biochar from around 8.0% to 80.0%. The Hg0 adsorption capacity of T6 was 36 times higher after Cl2 plasma modification. Plasma caused the biochar surface to become porous and promoted the thermal stability of the biochar. Sulfur (S) content remained in the range of 0.5–0.7%, elemental/organic sulfur and sulfide were converted to sulfate during plasma treatment. The relative intensity of the oxygen functional groups (C O, C O and C(O) O C) were enhanced, while the content of oxygen (O) in biochar decreased. The main reason for the improved mercury removal efficiency by modified biochars was attributed to the increased number of C Cl groups on the surface of the biochars induced by Cl2 plasma. The C Cl groups functioned as activated sites and promoted the Hg0 removal efficiency.

Compared to traditional biomass and coal-fired power plants, a process that includes integrated pyrolysis and subsequent gasification is a promising technology to deliver a larger electrical output through the production of high-purity hydrogen with a low carbon footprint. Chemical looping can further enhance the biomass contribution to the global renewable energy demand while fulfilling the stringent CO2 emission cuts needed in the energy sector. This study aims at investigating the feasibility of developing a solar catalytic chemical looping biomass refinery (SCCLBR) power plant for sustainable production of energy using a comprehensive plant modeling and techno-economic assessment. The plant is composed of 7 sequential units: i) biomass preparation (drying, transferring, and grinding), ii) reacting unit (SCCLBR), iii) water gas shift unit and heat recovery, iv) CO2 and H2S separation (Rectisol Process), v) sulfur removal (Claus Process), vi) air separation and vii) catalyst regeneration. The simulation was performed for 1–6 tonne/hour of biomass as input. The effect of key variables (feedstock load, water injection, and temperature) on the economic performance of the plant were analyzed. The simulated results of the chemical looping reactor were validated against the experimental results, while the results of Rectisol and air separation units were validated against the thermodynamic simulation. The results demonstrated that the CCLBR (without solar integration) and integrated SCCLBR can reach the efficiency of 34% and 41% respectively, yet the results have not been optimized. The sensitivity analysis indicated that water injection rate is the most influential parameter, which can even suppress the impact of biomass loading rate. A separate thermodynamic simulation was also performed to investigate the reaction equilibrium of oxygen carrier regeneration (Ca2Fe2O5) using CO2. The results demonstrated that a temperature above 730 °C is required to avoid carbonation (Fe2O3 and CaCO3 production). The maximum greenhouse gas emission in SCCLBR is 10.70, which is significantly lower than traditional coal-to-hydrogen and biomass-to-hydrogen power plants. It has also been found that across varying feedstock input rates, greenhouse gas emissions average 12.8% lower when solar PV supplements refinery power needs; optimization of the steam/biomass ratio may reduce emissions even further.

Primary particles emitted from fuel combustion mainly involve filterable particulate matter (FPM) and condensable particulate matter (CPM). Particularly, CPM has emerged as a subject for further emission control. This study investigated the effects of the sampling temperature and excess air coefficient (EAC) on the total mass, chemical speciation, and particle size distribution of CPM by integrating Electrical Low-Pressure Impactor+ (ELPI+) sampling devices with the EPA Method 202 (dry impinger method). The total mass of CPM increased with the sampling temperature and EAC. Specifically, the total concentration of CPM was 10.51–39.93 mg/m3, in which the mass fraction of organic species varied between 8.74 and 49.80%, and the organic components in CPM followed the ranking order of alkanes/alkenes (62.6–78.6%), oxygen-containing volatile organic compounds (OVOCs) (19.7–35.4%), and aromatics (5.6%). Compared with other inorganic species such as HCl and NOX, SO3 had a higher migration tendency from the flue gas to CPM. The particle size distribution suggested that heterogeneous condensation was responsible for the whole size range of particles in CPM, whereas the homogeneous condensation led to the increase of finer particles (smaller than 0.2 µm). Accordingly, adjusting the emission temperature and EAC could help to control the emission of CPM.

We report results of theoretical evaluation of the mechanisms of possible radical reactions on the edge-site of biochar with CO 2 · - , OH , and H in irradiated aqueous solution. The computational studies were performed for model poly aromatic systems. Obtained mechanisms reflect one of the routes of the oxygen loss accompanied by increase of hydrogen content, as observed in photochemical experiment. The reaction of CO 2 · - with the edge site of biochar mainly leads to reduced rather than oxidized products. The mechanism of CO2 capturing is mapped by different routes of one-electron reduction and radical addition to the aromatic ring.

Magnetization facilitates the separation and reuse of adsorbents, but significantly reduces the adsorption capacity. In this study, a double layer magnetized/functionalized biochar composite was synthesized through a hybrid post-pyrolysis magnetization which sustained and even significantly increased the adsorption capacity of microporous carbonaceous biochar (BC). The developed process included i) structural modification of biochar under ultrasound waves, ii) magnetization with magnetite (Fe3O4) nanoparticles, and iii) functionalization with 3-aminopropyltriethoxysilane (TES). Ultrasound irradiation exfoliates and breaks apart the irregular graphite layers of biochar, and creates new, or opens blocked, micropores, thus enhancing the BC’s porosity. For its part, TES stabilizes the magnetic nanoparticles on the biochar surface, while it participates in water decontamination through the strong chelation ability of its amino groups toward metal ions. Scanning electron microscopy demonstrated the stable and uniform distribution of Fe3O4 nanoparticles on the surface of microporous biochar, and Fourier-transform infrared spectroscopy indicated effective surface functionalization. In addition, although magnetization usually reduces the porosity of carbonaceous adsorbents, the ultraviolet–visible spectroscopic analysis showed that double layer magnetic biochar composite exhibited a much greater ability to remove Ni(II) and Pb(II), with 139 % and 38 % higher adsorptions than raw biochar. Almost complete removal of Pb (91 %) was observed by magnetic-BC and the adsorbent could easily be separated using a neodymium magnet. This high performance can be attributed to the synergistic effect of ultrasound activation on increasing the porosity and surface area of biochar along with enhanced chelation imparted by amine functionalization. The developed technique can be used for synthesizing advanced adsorbents for removal of nuclear waste-related metal ions from aqueous environments.

Biochar was subjected to N2-plasma treatment after adsorbing water or oxygen. The mercury removal efficiency of the obtained samples was tested. The results of H2O-thermogravimetric and O2-temperature programmed desorption show that biochar had adsorption capacity for both water and oxygen during storage. The adsorbed water exhibited an inhibitory effect on mercury removal. However, after plasma treatment, water decomposed into oxygen-containing active radicals and combined with biochar to form oxygen-containing functional groups. The generated functional groups compensated for the inhibition of mercury capture. After the biochar adsorbed oxygen, the biochar was easily sintered under plasma, thereby reducing the mercury removal performance. The oxygen-containing functional groups formed by plasma treatment of oxygen adsorbed biochar also improved the mercury removal efficiency. Hg-temperature programmed desorption revealed that Hg0 could be oxidised by the generated oxygen-containing functional group to form HgO. Correlation analysis showed that the oxygen adsorbed by the biochar from air during storage was the main source of oxygen-containing functional groups generated under a non-oxygen plasma environment. The correlation coefficient was up to 0.999. During normal storage, the oxygen adsorbed by the adsorbent from the air can be converted into oxygen-containing functional groups during the plasma modification process, thereby oxidising Hg0.

Conventional carbon activation requires heating carbon at a temperature greater than 700 °C for over 3 h, consuming 18,600 kcal/kg of activated biochar. In contrast, the ultrasound treatment method is conducted at ambient condition for a very short duration (∼30 s, which requires about 1135 kcal/kg of activated BC produced. The advanced low-temperature acoustic-based surface modification method not only increases the porosity and surface functionality of raw biochar, but also is economically feasible and environmentally friendly. As a sequel of our previous works, this study aims to investigate the interaction between ultrasonic-structural modification with four different pre-treatments including i) control with no pretreatment, ii) EDC/HBOt, iii) alkali using KOH, iv) acid using HNO3 or H3PO4. The process was then followed by amine functionalization with DEA (diethanolamine) for nickel removal. The results demonstrated that all acoustic-based amine-functionalized biochar samples, without any exception, had more amine- and oxygen-containing functional groups as well as micro porosity, compared to those aminated without acoustic-activation, particularly in samples pretreated with HNO3 and H3PO4. Despite an increase in porosity by ultrasonication, metal leaching from US-only samples and those activated with EDC/HOBt was observed during longer adsorption durations. However, the synergism created by the combined effect of ultrasound and KOH and H3PO4, not only enhanced the adsorption capacity of biochar but also significantly reduced the adsorption duration from 8 to 3 h. The highest nickel adsorptions were observed for ultrasonic-amine samples activated with H3PO4 > HNO3 ∼ KOH, which were far higher (60 %, 49 %, and 46 % more adsorption, without any leaching) than raw or US-biochar, or biochar aminated with EDC/HOBt or without pretreatment.