Activated Carbon from Sewage Sludge for Preconcentration of Copper

Adsorption of p-benzoquinone at low concentrations from aqueous media using biosolid-based activated carbon

The toxic oxidation intermediate p-benzoquinone exists in aqueous environments at dilute concentrations above the fish-toxicity limit of 0.045 mg/L, affecting aquatic life. The reduction of this compound to the concentrations required to achieve safe discharge limits is challenging. In this study, the adsorptive removal of p-benzoquinone by a biosolid-based activated carbon (SBAC) was systematically investigated in batch experiments. The adsorption rate was rapid, and the bulk of p-benzoquinone adsorption occurred within 30 min. The maximum adsorption capacity of SBAC was estimated at 19.6 mg/g using the Langmuir isotherm model. Its adsorptivity was independent of temperature from 6 to 40 °C. The presence of 6 g/L of chloride and 500 mg/L of sulphate did not affect the removal of 1 mg/L p-benzoquinone, whereas 15 mg/L of humic acid media slightly decreased the p-benzoquinone removal from 87.0% to 83.2%. Diffusion, hydrophilic, and electrostatic interactions (i.e., dipole-dipole) govern the adsorption of p-benzoquinone and are influenced by the SBAC surface chemistry. Biosolid-based activated carbon can lower the residual p-benzoquinone to below the fish-toxicity limit of 0.045 mg/L within 1 h of sequential adsorption. Thus, biosolid-based activated carbon can effectively remove p-benzoquinone from aqueous environments; this is a waste-to-resource approach that addresses sustainability (waste disposal) and environmental protection (pollutant removal).

Enhanced removal of neonicotinoid pesticides present in the Decision 2018/840/EU by new sewage sludge-based carbon materials

Due to the increasingly strict legislation about the disposal of sewage sludge, it is necessary to find sustainable solutions to manage this waste at low-cost conditions. In addition, priority contaminants are now attracting much attention since they are usually detected in WWTP effluents. In this work, five sludge have been used as precursors for the synthesis of activated carbons subsequently tested in the removal by adsorption of three neonicotinoid pesticides listed in the EU Watch List: acetamiprid (ACT), thiamethoxam (THM), and imidacloprid (IMD). Generally, the activated carbons were prepared by chemical activation using ZnCl₂ as an activating agent and then the resulting materials were pyrolyzed at 800 °C for 2 h. The synthesized activated carbons showed different textural properties; thus, the best adsorption results were found for AC-Industrial activated carbon, obtained from an industrial origin sewage sludge, with high equilibrium adsorption capacities (q_e = 104.2, 137.0, and 119.9 mg g^-1), for ACT, THM, and IMD, respectively. Furthermore, it was elucidated that the use of CO₂ in the synthesis generated an opening, followed by widening, of the narrowest microporosity, increasing the specific surface area of the carbon materials. The kinetic and isotherm adsorption experimental data were obtained for each of the pesticide-activated carbon systems; thus, the kinetic curves were well-fitted to the pseudo-second-order kinetic model, as well as, Freundlich and Guggenheim-Anderson-de Boer (GAB) empirical models were used for the fitting of the equilibrium adsorption isotherms, finding that GAB model best fitted the experimental data. Additionally, the regeneration of the activated carbons using methanol as a regenerating agent and the single and simultaneous adsorption of a hospital wastewater effluent, fortified with the three studied pesticides have been explored.

Synthesis and performance evaluation of adsorbents derived from sewage sludge blended with waste coal for nitrate and methyl red removal

Low-cost adsorbents were synthesized using two types of sewage sludge: D, which was obtained during the dissolved air flotation stage, and S, which was a mixture of primary and secondary sludge from the digestion and dewatering stages. The sewage sludge was mixed with waste coal before being activated with potassium hydroxide (KOH) and oxidized with ammonium persulfate (APS). The nitrate and methyl red removal capacities of the synthesized adsorbents were evaluated and compared to those of industrial activated charcoal. The oxidation surface area of adsorbents derived from sludge S shrank by six fold after modification i.e., from 281.72 (unoxidized) to 46.573 m2/g for the oxidized adsorbent with a solution of 2M ammonium peroxydisulfate, while those derived from D only varied narrowly from 312.72 to 282.22 m2/g, but surface modification had no effect on inorganic composition in either case. The adsorption of nitrate and methyl red (MR) was performed in batch mode, and the removal processes followed the pseudo second order kinetic model and the Langmuir isotherm fairly well. The adsorption capacities of nitrate and MR were higher at pH = 2 and pH = 4, respectively.

Preparation and Application of Efficient Biobased Carbon Adsorbents Prepared from Spruce Bark Residues for Efficient Removal of Reactive Dyes and Colors from Synthetic Effluents

Biobased carbon materials (BBC) obtained from Norway spruce (Picea abies Karst.) bark was produced by single-step chemical activation with ZnCl2 or KOH, and pyrolysis at 800 °C for one hour. The chemical activation reagent had a significant impact on the properties of the BBCs. KOH-biobased carbon material (KOH-BBC) had a higher specific surface area (SBET), equal to 1067 m2 g−1, larger pore volume (0.558 cm3 g−1), more mesopores, and a more hydrophilic surface than ZnCl2-BBC. However, the carbon yield for KOH-BBC was 63% lower than for ZnCl2-BBC. Batch adsorption experiments were performed to evaluate the ability of the two BBCs to remove two dyes, reactive orange 16 (RO-16) and reactive blue 4 (RB-4), and treat synthetic effluents. The general order model was most suitable for modeling the adsorption kinetics of both dyes and BBCs. The equilibrium parameters at 22 °C were calculated using the Liu model. Upon adsorption of RO-16, Qmax was 90.1 mg g−1 for ZnCl2-BBC and 354.8 mg g−1 for KOH-BBC. With RB-4, Qmax was 332.9 mg g−1 for ZnCl2-BBC and 582.5 mg g−1 for KOH-BBC. Based on characterization and experimental data, it was suggested that electrostatic interactions and hydrogen bonds between BBCs and RO-16 and RB-4 dyes played the most crucial role in the adsorption process. The biobased carbon materials showed high efficiency for removing RO-16 and RB-4, comparable to the best examples from the literature. Additionally, both the KOH- and ZnCl2-BBC showed a high ability to purify two synthetic effluents, but the KOH-BBC was superior.

Efficient removal of Hg2+ from aqueous solution by a novel composite of nano humboldtine decorated almandine (NHDA): Ion exchange, reducing-oxidation and adsorption

Efficient removal of Hg²⁺ from aqueous solution is key for environmental protection and human health. Herein, a novel composite of nano humboldtine decorated almandine was synthesized from almandine for the removal of Hg²⁺. Results showed that the Hg²⁺ removal process followed pseudo-second-order kinetic model and Langmuir equation, and the maximum adsorption capacity was 575.17 mg/g. Furthermore, Hg²⁺ removal by the composite was pH-dependent and low pH value facilitated the removal of Hg²⁺. SEM and HADDF-STEM results suggested a new rod morphology was generated and the adsorbed mercury was mainly enriched into this structure after reaction with Hg²⁺ solution. The removal mechanisms of Hg²⁺ by the composite was pH dependent, and included ion exchange, surface complexation, reduction and oxidation. Our results demonstrated that the composite was an ideal material for Hg²⁺ removal and the transformation ways of mercury related species could be a significant but currently underestimated pathway in natural and engineered systems.

A Short Review on the Electrochemical Performance of Hierarchical and Nitrogen-Doped Activated Biocarbon-Based Electrodes for Supercapacitors

Cheap and efficient carbon electrodes (CEs) for energy storage systems (ESS) such as supercapacitors (SCs) and batteries are an increasing priority issue, among other things, due to a globally increasing share of intermittent electricity production (solar and wind) and electrification of transport. The increasing consumption of portable and non-portable electronic devices justifies research that enables environmentally and economically sustainable production (materials, processing techniques, and product design) of products with a high electrochemical performance at an acceptable cost. Among all the currently explored CEs materials, biomass-based activated carbons (AC) present enormous potential due to their availability and low-cost, easy processing methods, physicochemical stability, and methods for self-doping. Nitrogen doping methods in CEs for SCs have been demonstrated to enhance its conductivities, surface wettability, and induced pseudocapacitance effect, thereby delivering improved energy/power densities with versatile properties. Herein, a short review is presented, focusing on the different types of natural carbon sources for preparing CEs towards the fabrication of SCs with high electrochemical performance. The influences of ACs' pore characteristics (micro and mesoporosity) and nitrogen doping on the overall electrochemical performance (EP) are addressed.

Extremely efficient and rapidly adsorb methylene blue using porous adsorbent prepared from waste paper: Kinetics and equilibrium studies

For the first time, zinc chloride activation method was used to prepare waste paper-based activated carbon in this study. The structure, morphology, surface functional groups and particle size distribution of the activated carbon was study using automatic specific surface area analyzer, FTIR, Boehm titration, X-ray diffraction, SEM and EDS. The specific surface area of the activated carbon is up to 1987 m²/g. Cumulative pore volume is up to 2.586 cm³/g, with micropore volume accounting for 92 %. Methylene blue adsorption performance results shown that the adsorbent has achieved high removal efficiency (99.65 % in 10 min, uptake = 996.5 mg/g), its maximum adsorption capacity has reached 1657 mg/g. The pH_pzc of the adsorbent was determined to explore the adsorption mechanism, its results shown that electrostatic adsorption occurs between adsorbents and adsorbents at pH higher than pH_pzc (pH_pzc = 3.2). Moreover, adsorption mechanism was studied by various isothermal models, thermodynamic models, kinetic models. Redlich-Peterson isotherm model best describes the adsorption experiment, which indicated that the adsorption follows a non-ideal and mixed adsorption mechanism. Methylene blue molecules gone into micropore was the adsorption rate-limiting step, and MB adsorption by the waste paper-based adsorbent was a spontaneous, endothermic and randomly increasing adsorption. Simulated wastewater and regeneration experiments were also used to evaluate the adsorbent's treatment capacity and economic efficiency, and these results indicated that the adsorbent has good decolorization and regeneration ability.

Microwave-assisted synthesis of β-cyclodextrin functionalized celluloses for enhanced removal of Pb(II) from water: Adsorptive performance and mechanism exploration

Herein, β-cyclodextrin (β-CD) was efficiently grafted onto rice husk-based celluloses using different cross-linking agents of epichlorohydrin (EPI) and glutaraldehyde (GA). By feat of microwave irradiation, the functionalization procedure was completed in 17 min, and the synthesized RHEPIMWβ-CD and RHGAMWβ-CD exhibited fast adsorption equilibrium for Pb(II) within 20 min, excellent monolayer adsorption capacities of 216.06 and 279.08 mg g^-1 across an extensive pH scope of 3.0-6.0, unaffected affinity to Pb(II) during the existence of co-existing ions, superior reusability with over 81% and 87% of Pb(II) uptake sustained for four adsorption-desorption cycles. Thermodynamic parameters implied that the uptake process of Pb(II) occurred spontaneously (-ΔG⁰) with an endothermic characteristic (+ΔH⁰). Furthermore, electrostatic attraction and complexation were demonstrated to enhance the Pb(II) uptake onto the RHEPIMWβ-CD and RHGAMWβ-CD. In fix-bed columns, these two adsorbents also efficiently eliminated Pb(II) under various flow rates with experimental breakthrough curves well simulated by Thomas and Yoon-Nelson models. Significantly, the RHEPIMWβ-CD and RHGAMWβ-CD could effectively purify acid battery effluent containing Pb(II) for meeting regulatory requirement. Overall, the fast fabrication, excellent adsorption and recycling performance facilitate the development of tailored adsorbents for Pb(II) elimination in wastewater.

KOH-activated porous biochar with high specific surface area for adsorptive removal of chromium (VI) and naphthalene from water: Affecting factors, mechanisms and reusability exploration

Herein, a high-performance porous biochar described as PBC_KOH was successfully synthesized by two-step pyrolysis of corn straw with chemical activation of KOH, and was employed for the elimination of Cr(VI) and naphthalene (NAP) from water. Benefiting from KOH activation, the PBC_KOH was found to possess huge specific surface area of 2183.80 m²/g and many well-developed micropores with average particle size of 2.75 nm and main pore diameters distribution from 1 to 2 nm. The PBC_KOH presented an excellent adsorption performance with a theoretical monolayer uptake of 116.97 mg/g for Cr(VI) and a heterogeneous adsorption capacity of 450.43 mg/g for NAP. The uptake equilibrium was attained within about 120 min for Cr(VI), while about 180 min for NAP following avrami fractional-order model, revealing the existence of multiple kinetics during the adsorption. The thermodynamic results showed that the uptake of both Cr(VI) and NAP occurred spontaneously (-ΔG°), while in an endothermic nature for Cr(VI) (+ΔH°) and an exothermic characteristic for NAP (-ΔH°) with different randomness. Furthermore, the PBC_KOH was believed to enhance the Cr(VI) adsorption mainly through the combination of electrostatic attraction, complexation, ion exchange and reduction action, while achieving the high NAP uptake by pore filling and π-π stacking interactions.

Oil industry waste based non-magnetic and magnetic hydrochar to sequester potentially toxic post-transition metal ions from water

Solid waste conversion to value-added products is a stepping stone towards sustainable environment. Herein, sesame oil cake (SOC), an oil industry waste was utilized as a precursor to develop hydrochar (HC) samples by varying reaction temperature (150-250 °C) and time span (2-8 h), chemically treated with 10% H₂O₂ to optimize a sample with maximum yield and Pb(II) adsorption. Highest yield (29.2 %) and Pb(II) (24.57 mg/g at C_o: 15 mg/L) adsorption was observed on SOCHC@200 °C/6 h, magnetized (mSOCHC@200 °C/6 h) for comparative study. XRD displayed highly crystalline SOCHC@200 °C/6 h and amorphous mSOCHC@200 °C/6 h, both having a characteristic cellulose peak at 14.9°. mSOCHC@200 °C/6 h displayed superparamagnetic behavior with 11.2 emu/g saturation magnetization. IR spectra confirmed the development of samples rich in oxygen containing functionalities; an additional peak for iron oxides appeared at 586 cm^-1 in mSOCHC@200°C/6 h spectrum. Four major peaks at 531.9, 399.9, 348.2 and 284.7 eV, assigned to O 1s, N 1s, Ca 2p and C 1s, respectively were observed during XPS analyses. An additional peak at 710.3 eV, ascribed to Fe 2p was observed in mSOCHC@200C/6 h XPS spectrum, while a peak at 143.2 eV for Pb 4f appeared in spectra of both Pb(II) saturated samples. pH dependent (maximum at ∼6.7), exothermic Pb(II) adsorption was found. About 50-70% (at C_o: 25 mg/L) adsorption on both SOCHC@200 °C/6 h and mSOCHC@200 °C/6 h was accomplished in a minute, attaining equilibrium in 180 and 240 min, respectively. Error functions and superimposed q_{e, exp}. and q_{e, cal.} values supported Langmuir isotherm model applicability, with respective q_m values of 304.9 and 361.7 mg/g at 25 °C for SOCHC@200 °C/6 h and mSOCHC@200 °C/6 h. Kinetic data was fitted to PSO model. Highest (between 92.2 and 88.9 %) amount of Pb(II) from SOCHC@200 °C/6 h and mSOCHC@200 °C/6 h was eluted by 0.01 M HCl.

Sustainable Biomass Activated Carbons as Electrodes for Battery and Supercapacitors-A Mini-Review

Some recent developments in the preparation of biomass carbon electrodes (CEs) using various biomass residues for application in energy storage devices, such as batteries and supercapacitors, are presented in this work. The application of biomass residues as the primary precursor for the production of CEs has been increasing over the last years due to it being a renewable source with comparably low processing cost, providing prerequisites for a process that is economically and technically sustainable. Electrochemical energy storage technology is key to the sustainable development of autonomous and wearable electronic devices. This article highlights the application of various types of biomass in the production of CEs by using different types of pyrolysis and experimental conditions and denotes some possible effects on their final characteristics. An overview is provided on the use of different biomass types for the synthesis of CEs with efficient electrochemical properties for batteries and supercapacitors. This review showed that, from different biomass residues, it is possible to obtain CEs with different electrochemical properties and that they can be successfully applied in high-performance batteries and supercapacitors. As the research and development of producing CEs still faces a gap by linking the type and composition of biomass residues with the carbon electrodes' electrochemical performances in supercapacitor and battery applications, this work tries to diminish this gap. Physical and chemical characteristics of the CEs, such as porosity, chemical composition, and surface functionalities, are reflected in the electrochemical performances. It is expected that this review not only provides the reader with a good overview of using various biomass residues in the energy storage applications, but also highlights some goals and challenges remaining in the future research and development of this topic.

Microwave-activated carbons from tucumã (Astrocaryum aculeatum) seed for efficient removal of 2-nitrophenol from aqueous solutions

Activated carbons (ACs) prepared from tucumã seed (Astrocaryum aculeatum) were used for 2-nitrophenol removal from aqueous solutions. The ACs were characterized by elemental analysis, FTIR, N₂ adsorption/desorption isotherms, TGA, hydrophobicity/hydrophilicity balance, and total of acidic and basic groups. The ACs showed to have hydrophilic surfaces and they presented high specific surface areas (up to 1318 m² g^-1). In batch optimization studies, maximum removal was obtained at pH 7, contact time of 30 min, adsorbent dosage 1.5 gL^-1 and temperature of 50°C. The general-order kinetic model and Liu isotherm model best fit the kinetic and equilibrium adsorption data with a maximum adsorption capacity of 1382 mg g^-1 at 50°C. Effect of temperature and thermodynamic studies revealed that the adsorption processes of 2-nitrophenol onto ACs are dependent on temperature and are exothermic and spontaneous, respectively. About the applicability of the ACs for treating simulated effluents, the tucumã seed-activated carbon showed an excellent outcome in the treatment of simulated effluents, evidencing its high efficiency for phenolic compound adsorption. Tucumã seed-ACs showed to be cost effective and highly efficient adsorbents for efficient removal of 2-nitrophenol from aqueous solutions.

Tuning role and mechanism of paint sludge for characteristics of sewage sludge carbon: Paint sludge as a new macro-pores forming agent

For the first time, paint sludge waste (PS) was used as a pore forming agent in the preparation of sewage sludge derived carbon (SC). The tuning role and mechanism of PS for characteristics of SC were explored. It was found that a sludge carbon (SC_PS-Zn) with rich macro-, meso- and micro- porous could be produced by one-step pyrolytic process of sludge in the presence of PS and ZnCl_2. Its surface area could reach as high as 680.5m²g^-1 as 88.4 times and 4.8 times of sludge carbon without addition of PS and ZnCl₂ (SC) and only addition of ZnCl₂ (SC_Zn)_, respectively. The macro- pores fabricated by PS provided much inner-space for ZnCl₂ to generate meso- and micro- porous, leading to a hierarchical porous structure. SC_PS-Zn showed a high adsorption capacity of 685.4mgg^-1 for Chrysophenine, which is 1.3 and 1.7 times that of SC_PS and SC_Zn respectively. The adsorption difference could be simply attributed to the fact that the great molecules were difficult to enter micro- pores of SC_Zn. It was also found that the difference was also dependent on orientation of Chrysophenine, which was related to pH value of solution.

Sustainable pyrolytic sludge-char preparation on improvement of closed-loop sewage sludge treatment: Characterization and combined in-situ application

Aiming at closed-loop sustainable sewage sludge treatment, an optimal and economical pyrolytic temperature was found at 400-450 °C considering its pyrolysis efficiency of 65%, fast cracking of hydrocarbons, proteins and lipids and development of aromatized porous structure. Fourier-transform infrared (FTIR) and X-ray diffraction (XRD) tests demonstrated the development of adsorptive functional groups and crystallographic phases of adsorptive minerals. The optimal sludge-char, with a medium specific surface area of 39.6 m² g^-1 and an iodine number of 327 mgI₂ g^-1, performed low heavy metals lixiviation. The application of sludge-char in raw sewage could remove 30% of soluble chemical oxygen demand (SCOD), along with an acetic acid adsorption capacity of 18.0 mg g^-1. The developed mesopore and/or macropore structures, containing rich acidic and basic functional groups, led to good biofilm matrices for enhanced microbial activities and improved autotrophic nitrification in anoxic stage of an A/O reactor through adsorbed extra carbon source, and hence achieved the total nitrogen (TN) removal up to 50.3%. It is demonstrated that the closed-loop sewage sludge treatment that incorporates pyrolytic sludge-char into in-situ biological sewage treatment can be a promising sustainable strategy by further optimization.