Synthesis, Characterization, and Dye Removal of ZnCl2-Modified Biochar Derived from Pulp and Paper Sludge

Synthesis and characterization of nanobiochar from rice husk biochar for the removal of safranin and malachite green from water

Xenobiotic pollution in environment is a potential risk to marine life, and human health. Nanobiotechnology is an advanced and emerging solution for the removal of environmental pollutants. Adsorption-based technologies are being used to alleviate the global prevalence of xenobiotics like dyes, due to their high efficacy and cost effectiveness. Current study explored the potential of nanobiochar syntehsized via ultrasonication and centrifugation from rice husk for dye removal from water. It involves the synthesis of nanobiochar from rice husk biochar for removal of Safranin, Malachite green, and a mixture of both from aqueous water. Biochar was synthesized through pyrolysis at 600 °C for 2 h. To convert it into nanobiochar, sonication and centrifugation techniques were applied. The yield obtained was 27.5% for biochar and 0.9% for nanobiochar. Nanobiochar analysis through Fourier-Transform Spectrometer (FTIR), X-ray Power Diffraction (XRD) and scanning electron microscopy (SEM) suggested its crystalline nature having minerals rich in silicon, with a cracked and disintegrated carbon structure due to high temperature and processing treatments. Removal of dyes by nanobiochar was evaluated by changing different physical parameters i.e., nanobiochar dose, pH, and temperature. Pseudo-first order model and pseudo-second order model were applied to studying the adsorption kinetics mechanism. Kinetics for adsorption of dyes followed the pseudo-second order model suggesting the removal of dyes by process of chemical sorption. High adsorption was found at a higher concentration of nanobiochar, high temperature, and neutral pH. Maximum elimination percentages of safranin, malachite green, and a mixture of dyes were obtained as 91.7%, 87.5%, and 85% respectively. We conclude that nanobiochar could be a solution for dye removal from aqueous media.

Conversion of solid wastes and natural biomass for deciphering the valorization of biochar in pollution abatement: A review on the thermo-chemical processes

This overview addresses the formation of solid trash and the various forms of waste from a variety of industries, which environmentalists have embraced. The paper investigates the negative effects on the environment caused by unsustainable management of municipal solid trash as well as the opportunities presented by the formal system. This examination looks at the origins of solid waste as well as the typical treatment methods. Pyrolysis methods, feedstock pyrolysis, and lignocellulosic biomass pyrolysis were highlighted. Explain in detail the various thermochemical processes that take place during the pyrolysis of biomass. Due to its carbon content, low cost, accessibility, ubiquitousness, renewable nature, and environmental friendliness, biomass waste is a unique biochar precursor. This study looks at the different types of biomass waste that are available for treating wastewater. This study discussed a wide variety of reactors. Adsorption is the standard method that is used the most frequently to remove hazardous organic, dye, and inorganic pollutants from wastewater. These pollutants cause damage to the environment and water supplies, thus it is important to remove them. Adsorption is both simple and inexpensive to utilize. Temperature-dependent conversions explain the kinetic theories of biomaterial biochemical degradation. This article presents a review that explains how pyrolytic breakdown char materials can be used to reduce pollution and improve environmental management.

Biochar-based geopolymer nanocomposite for COD and phenol removal from agro-industrial biorefinery wastewater: Kinetic modelling, microbial community, and optimization by response surface methodology

Agro-industrial biorefinery effluent (AIBW) is considered a highly polluting source responsible for environmental contamination. It contains high loads of chemical oxygen demand (COD), and phenol, with several other organic and inorganic constituents. Thus, an economic treatment approach is required for the sustainable discharge of the effluent. The long-term process performance, contaminant removal and microbial response of AIBW to rice straw-based biochar (RSB) and biochar-based geopolymer nanocomposite (BGC) as biosorbents in an activated sludge process were investigated. The adsorbents operated in an extended aeration system with a varied hydraulic retention time of between 0.5 and 1.5 d and an AIBW concentration of 40-100% for COD and phenol removal under standard conditions. Response surface methodology was utilised to optimize the process variables of the bioreactor system. Process results indicated a significant reduction of COD (79.51%, 98.01%) and phenol (61.94%, 74.44%) for BEAS and GEAS bioreactors respectively, at 1 d HRT and AIBW of 70%. Kinetic model analysis indicated that the Stover-Kincannon model best describes the system functionality, while the Grau model was better in predicting substrate removal rate and both with a precision of between R2 (0.9008-0.9988). Microbial communities examined indicated the abundance of genera, following the biosorbent addition, while RSB and BGC had no negative effect on the bioreactor's performance and bacterial community structure of biomass. Proteobacteria and Bacteroidetes were abundant in BEAS. While the GEAS achieved higher COD and phenol removal due to high Nitrosomonas, Nitrospira, Comamonas, Methanomethylovorans and Acinetobacter abundance in the activated sludge. Thus, this study demonstrated that the combination of biosorption and activated sludge processes could be promising, highly efficient, and most economical for AIBW treatment, without jeopardising the elimination of pollutants or the development of microbial communities.

Co-pyrolysis of textile dyeing sludge/litchi shell and CaO: Immobilization of heavy metals and the analysis of the mechanism

To relieve the secondary contamination of heavy metals (HMs), the synergistic effect of co-pyrolysis of textile dyeing sludge (DS)/litchi shell (LS) and CaO on the migration of HMs was demonstrated in this study. The proportions of Cu, Zn, Cr, Mn, and Ni in the F4 fraction increased to 75%, 55%, 100%, 50%, and 62% at the suitable CaO dosages. When 10% CaO was added, the RI value of DLC-10% was reduced to 7.89, indicating low environmental risk. The characterizations of the physicochemical properties of biochar provided support for the HMs immobilization mechanism. HMs combined with inorganic minerals or functional groups to form new stable HMs crystalline minerals and complexes to achieve immobilization of HMs. The pH value and pore structure also play an important role in improving the immobilization performance of HMs. In conclusion, the results provided a new direction for the subsequent harmless treatment of HMs-enriched waste.

Formation of self-nitrogen-doping activated carbon from Fish/sawdust/ZnCl2 by hydrothermal and pyrolysis for toxic chromium adsorption from wastewater

This study gives a description of the formation of self-nitrogen doped activated carbon (NDAC) by a novel way of employing fish meal (mixture of Atherina hepseetus and Sardina pilchardus of 60% protein) as nitrogen dopant, ZnCl₂ as impregnate agent, sawdust as carbon source and water with a mass ratio (2:1:1:12), which subjected to the hydrothermal process. The hydrothermal mixture was oven dried and carbonized under a flow of nitrogen for one h at 600, 700, and 800 °C. The characterization of NDAC was performed by using various analytical techniques analyses. The synthesized NDAC exhibited unique features such as microporous structure (1.84 ~ 2.01 nm), high surface area (437.51 ~ 680.86 m²/g), the volume of total pores (0.22 ~ 0.32 cm³/g) and nitrogen content (12.82 ~ 13.73%). Batch removal tests were achieved to investigate the impact of chromium ions starting concentration (100-400 mg/L), NDAC dose (0.5-2.5 g/L), pH and contact time (5-120 min). Such helpful characteristics of NDAC, particularly for NDAC600, were suitable to use as an excellent adsorbent for Cr⁶⁺ ions with a maximum adsorption capacity (Q_m) (769.23 mg/g), and the highest chromium ions adsorption uptake (81.18%) was obtained at pH value 1.5 at room temperature. Both Halsey and Temkin models fitted the adsorption data quite reasonably. The uptake of toxic chromium ions is best represented with pseudo-second-order rate kinetics data.

Mono- and Multicomponent Biosorption of Caffeine and Salicylic Acid onto Processed Cape Gooseberry Husk Agri-Food Waste

There is an increasing need to find cost-effective and sustainable solutions for treating wastewater from contaminants of emerging concern (CECs). In this regard, cape gooseberry husk-typically an agri-food waste-is investigated for the first time as a potential biosorbent for the removal of model pharmaceutical contaminants of caffeine (CA) and salicylic acid (SA) from water. Three different preparations of husks were investigated and characterized using Fourier transform infrared spectroscopy, scanning electron microscopy, Brunauer-Emmett-Teller analysis, zeta potential, and point of zero charge measurements. The activation of the husk led to an increase in the surface area, pore volume, average pore size, and adsorption favorability. The single-component adsorption of SA and CA onto the three husks was investigated at different initial concentrations and pH values to determine the optimal operating conditions. The maximal removal efficiencies of SA and CA reached up to 85 and 63%, respectively, for the optimal husk which also offers a less energy-intensive option in its activation. This husk also exhibited high rates of adsorption that exceeded other husk preparations by up to four times. It was proposed that CA interacts electrostatically with the husk, while SA binds through weak physical interactions (e.g., van der Waals and H-bonding). In binary systems, CA adsorption was highly favored over SA adsorption, owing to its electrostatic interactions. The selectivity coefficients α_SA^CA varied with initial concentration and ranged between 61 and 627. The regeneration of husk was also successful resulting in its re-use for up to four full consecutive cycles, further demonstrating the efficiency of cape gooseberry husk use in wastewater treatment.

Valorization of Ginger Waste-Derived Biochar for Simultaneous Multiclass Antibiotics Remediation in Aqueous Medium

The presence of antibiotics in the aqueous environment has been a serious concern primarily due to the development of antimicrobial resistance (AMR) in diverse microbial populations. To overcome the rising AMR concerns, antibiotic decontamination of the environmental matrices may play a vital role. The present study investigates the use of zinc-activated ginger-waste derived biochar for the removal of six antibiotics belonging to three different classes, viz., β-lactams, fluoroquinolones, and tetracyclines from the water matrix. The adsorption capacities of activated ginger biochar (AGB) for the concurrent removal of the tested antibiotics were investigated at different contact times, temperatures, pH values, and initial concentrations of the adsorbate and adsorbent doses. AGB demonstrated high adsorption capacities of 5.00, 17.42, 9.66, 9.24, 7.15, and 5.40 mg/g for amoxicillin, oxacillin, ciprofloxacin, enrofloxacin, chlortetracycline, and doxycycline, respectively. Further, among the employed isotherm models, the Langmuir model fitted well for all the antibiotics except oxacillin. The kinetic data of the adsorption experiments followed the pseudo-second order kinetics suggesting chemisorption as the preferred adsorption mechanism. Adsorption studies at different temperatures were conducted to obtain the thermodynamic characteristics suggesting a spontaneous exothermic adsorption phenomenon. AGB being a waste-derived cost-effective material shows promising antibiotic decontamination from the water environment.

Oil tea shell synthesized biochar adsorptive utilization for the nitrate removal from aqueous media

Various reported methods are devoted to nitrate removal from water over the years. However, recently researchers are focusing on developing the materials that offer bio-based, non-toxic, inexpensive and yet an efficient solution for water treatment. In this study, removal of nitrates from water was carried out using oil tea shells (OTS) as a biosorbent. OTS powder was impregnated with ZnCl₂ and biochar was prepared which was further treated with Cetyltrimethylammonium bromide (CTAB), a cationic surfactant. Both the Langmuir and the Freundlich models were satisfied by the nitrate adsorption of OTS biochar. The adsorption capacity was measured at 15.6 mg/g when the circumstances were at their best. The pseudo-second-order model provided an accurate description of the kinetic data that were collected from batch trials. The adsorption yield goes up when by usage of more adsorbent, but it goes down when adsorption start with a higher concentration of nitrate. The strong basis of analytical equipments were used to characterize the OTS biosorbent. According to the findings of the research, surface-modified OTS biochar is an effective material for the removal of nitrate from aqueous solutions. This means that it has the potential to be utilized in water treatment as an adsorbent that is both inexpensive and kind to the natural environment. Removal of heavy metals and other organic pollutants, both from groundwater and wastewater using OTS biochar seems like a promising and interesting area of study.

A sustainable reuse strategy of converting waste activated sludge into biochar for contaminants removal from water: Modifications, applications and perspectives

Conversion of sewage sludge to biochar for contaminants removal from water achieves the dual purpose of solid waste reuse and pollution elimination, in line with the concept of circular economy and carbon neutrality. However, the current understanding of sludge-derived biochar (SDB) for wastewater treatment is still limited, with a lack of summary regarding the effect of modification on the mechanism of SDB adsorption/catalytic removal aqueous contaminants. To advance knowledge in this aspect, this paper systematically reviews the recent studies on the use of (modified) SDB as adsorbents and in persulfate-based advanced oxidation processes (PS-AOPs) as catalysts for the contaminants removal from water over the past five years. Unmodified SDB not only exhibits stronger cation exchange and surface precipitation for heavy metals due to its nitrogen/mineral-rich properties, but also can provide abundant catalytic active sites for PS. An emphatic summary of how certain adsorption removal mechanisms of SDB or its catalytic performance in PS-AOPs can be enhanced by targeted regulation/modification such as increasing the specific surface area, functional groups, graphitization degree, N-doping or transition metal loading is presented. The interference of inorganic ions/natural organic matter is one of the unavoidable challenges that SDB is used for adsorption/catalytic removal of contaminants in real wastewater. Finally, this paper presents the future perspectives of SDB in the field of wastewater treatment. This review can contribute forefront knowledge and new ideas for advancing sludge treatment toward sustainable green circular economy.

A Novel Low-Cost Bio-Sorbent Prepared from Crisp Persimmon Peel by Low-Temperature Pyrolysis for Adsorption of Organic Dyes

In order to properly reuse food waste and remove various contaminants from wastewater, the development of green, sustainable and clean technologies has demonstrated potential in the efficient inhibition of secondary pollution to the environment. In this study, an economical and green method was used to prepare biochar from crisp persimmon peel (CPP) using flash-vacuum pyrolysis at different temperatures (200–700 °C; referred to as CPP200–CPP700). CPP200 has high polarity, low aromaticity and high oxygen-containing functional groups that exhibit superior MB adsorption capabilities. CPP200 that was prepared at a relatively low temperature of 200 °C exhibited a high adsorption capacity of 59.72 mg/g toward methylene blue (MB), which was relatively higher than that for alizarin yellow R (4.05 mg/g) and neutral red (39.08 mg/g), indicating that CPP200 possesses a higher adsorption selectivity for cationic dyes. Kinetics investigation revealed that the kinetic data of CPP200 for the adsorption of MB was better fitted by a linear pseudo-second-order model. Isothermal studies indicated that the linear Langmuir model was more suitable for describing the adsorption process. The adsorption thermodynamics illustrated that the adsorption of MB onto CPP200 was spontaneous and endothermic. EDS and IR analyses of CPP200 for both pre- and post-adsorption of MB showed that electrostatic interactions between oxygen-containing groups on biochar and target MB dominated the adsorption procedure, in addition to hydrogen bonding interactions. Reusability tests confirmed the excellent regeneration characteristics of CPP200, indicating that CPP200 may be used as a green, sustainable, highly efficient and recyclable adsorbent for the selective removal of cationic organic dyes.

Surface Modification of Biochar for Dye Removal from Wastewater

Nowadays, biochar is being studied to a great degree because of its potential for carbon sequestration, soil improvement, climate change mitigation, catalysis, wastewater treatment, energy storage, and waste management. The present review emphasizes on the utilization of biochar and biochar-based nanocomposites to play a key role in decontaminating dyes from wastewater. Numerous trials are underway to synthesize functionalized, surface engineered biochar-based nanocomposites that can sufficiently remove dye-contaminated wastewater. The removal of dyes from wastewater via natural and modified biochar follows numerous mechanisms such as precipitation, surface complexation, ion exchange, cation–π interactions, and electrostatic attraction. Further, biochar production and modification promote good adsorption capacity for dye removal owing to the properties tailored from the production stage and linked with specific adsorption mechanisms such as hydrophobic and electrostatic interactions. Meanwhile, a framework for artificial neural networking and machine learning to model the dye removal efficiency of biochar from wastewater is proposed even though such studies are still in their infancy stage. The present review article recommends that smart technologies for modelling and forecasting the potential of such modification of biochar should be included for their proper applications.

Conversion of Industrial Sludge into Activated Biochar for Effective Cationic Dye Removal: Characterization and Adsorption Properties Assessment

This paper presents an in-depth characterization of a raw industrial sludge (IS-R) and its KOH-activated biochar pyrolyzed at 750 °C (IS-KOH-B) followed by their application to remove a cationic dye from aqueous solution. Materials characterization shows that compared to the IS-R, the IS-KOH-B has improved structural, textural, and surface chemical properties. In particular, the IS-KOH-B’s BET surface area and total pore volume are about 78 and 6 times higher than those found for the IS-R, respectively. The activated biochar efficiently retained the cationic dye under wide experimental conditions. Indeed, for an initial dye concentration of 50 mg L−1, removal yields were assessed to be more than 92.5%, 93.5%, and 97.8% for a large pH range (4–10), in the presence of high contents of competing cations (3000 mg L−1 of Ca2+, Mg2+, Na+, and K+), and a low used adsorbent dose (1 g L−1), respectively. The Langmuir’s adsorption capacities were 48.5 and 65.9 mg g−1 for of IS-R and IS-KOH-B, respectively, which are higher than those reported for various adsorbents in the literature. The dye removal was found to be monolayer, spontaneous, and endothermic for both the adsorbents. Moreover, this removal process seems to be controlled by chemical reactions for IS-KOH-B whereas by both physico–chemical reactions for IS-R. This study demonstrates that the raw industrial sludge and especially its KOH-activated derived biochar could be considered as promising adsorbents for the removal of dyes from aqueous solutions.