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Activated carbon (AC) with high specific surface area was prepared by using bifunctional H 3 PO 4 agent, which led to dehydrating and activation effects through hydrothermal pretreatment and subsequent pyrolysis process. N 2 adsorption and desorption isotherms of AC showed a high BET surface area of 2434 m 2  g -1 and a total volume of pores (V T ) of 2.0447 m 3  g -1 for AC. The morphology and the chemical components of hydrochar and AC were characterized by scanning electron microscopy and Fourier transform infrared spectroscopy, which indicated that H 3 PO 4 was benefitting for the formation of porous structure of AC. Subsequently, the effect of H 3 PO 4 in hydrothermal pretreatment and activation process was investigated by comparative experiments. The removal and adsorption of methylene blue (MB) dye with different concentrations onto the AC were studied. The monolayer equilibrium adsorption capacity was 644 mg g -1 , showing that AC has good adsorption qualities for methylene blue (MB). The adsorption balance data of MB on AC was best fitted to the Redlich-Peterson model. The adsorption kinetic data fit better to the pseudo-first-order model at low MB concentration, and the pseudo-second-order and Elovich models fit better when the MB concentration was rising.

Here, the chemical modification of Ziziphus jujuba stones (ZJS) treated with ortho-phosphoric acid (ZJS-H3PO4) is investigated to enhance its adsorption properties for organic dyes. The physicochemical properties of ZJS-H3PO4 reveal increased porosity (87.29%), slightly higher bulk density (0.034 g mL−1), and enhanced acidity (31.42 m eq g g−1) compared to untreated ZJS. XRF analysis confirms the successful incorporation of orthophosphoric acid during treatment due to a significant increase in phosphorus content. The maximum adsorption capacity of methylene blue on ZJS-H3PO4 is found to be 179.83 mg g−1, demonstrating its efficacy as a potential adsorbent for organic dyes. These findings suggest that modifying ZJS with orthophosphoric acid could be a promising strategy to enhance its adsorption performance in various environmental applications. Furthermore, Gaussian process regression (GPR) is employed to model MB adsorption by ZJS-H3PO4. Optimization of the GPR model involves evaluating different kernel functions and meticulously adjusting parameters to maximize its ability to capture complex relationships in the data. The obtained GPR model demonstrates remarkable performance with high correlation coefficients (R) and low root mean square errors (RMSEs) across all study phases. Model validation is performed through residual analysis, confirming its effectiveness and accuracy in predicting MB adsorption. Finally, a user-friendly interface is developed to facilitate the usage of the GPR model in future applications, representing a significant advancement in environmental process modeling and ecosystem management. [ABSTRACT FROM AUTHOR]

Activated carbon was prepared from Chinese prickly seeds activated by H3PO4. It was characterized by the methods of FT-IR, N2 adsorption/desorption, XRD, SEM and EDS. The adsorption performance for methylene blue was investigated. Under the conditions that impregnation mass ratio of 85 wt% H3PO4 to Chinese prickly seeds was 0.8, impregnation time was 10 h, carbonization temperature was 550 ℃ and carbonization time was 60 min, activated carbon containing micro- and meso-porous was prepared successfully with the yield and BET specific area were 23.4% and 740 m²/g, respectively. The adsorption for methylene blue investigation showed the adsorption capacity could be achieved to 495 mg·g when the initial concentration of methylene blue is 500 mg·L under the adsorption temperature at 30℃ and pH of 13.0 after adsorbed for 60 min. Thermodynamics studies showed the adsorption process can be favorably described by Langmuir isotherm that ΔH is 33.7 kJ·mol and ΔS is 125.9 J/(mol·℃). The adsorption kinetics was satisfactory fitted to the pseudo-second-order model that the activated energy is 6.33 kJ/mol. The study provides a reference for the high-quality utilization of Chinese brickly seeds and the useful dada for the adsorption treatment of dye wastewater by activated carbon preparation from Chinese brickly seeds. [ABSTRACT FROM AUTHOR]

Herein, tropical fruit biomass wastes including durian seeds (DS) and rambutan peels (RP) were used as sustainable precursors for preparing activated carbon (DSRPAC) using microwave-induced H3PO4 activation. The textural and physicochemical characteristics of DSRPAC were investigated by N2 adsorption-desorption isotherms, X-ray diffraction, Fourier transform infrared, point of zero charge, and scanning electron microscope analyses. These findings reveal that the DSRPAC has a mean pore diameter of 3.79 nm and a specific surface area of 104.2 m2/g. DSRPAC was applied as a green adsorbent to extensively investigate the removal of an organic dye (methylene blue, MB) from aqueous solutions. The response surface methodology Box–Behnken design (RSM-BBD) was used to evaluate the vital adsorption characteristics, which included (A) DSRPAC dosage (0.02–0.12 g/L), (B) pH (4–10), and (C) time (10–70 min). The BBD model specified that the DSRPAC dosage (0.12 g/L), pH (10), and time (40 min) parameters caused the largest removal of MB (82.1%). The adsorption isotherm findings reveal that MB adsorption pursues the Freundlich model, whereas the kinetic data can be well described by the pseudo-first-order and pseudo-second-order models. DSRPAC exhibited good MB adsorption capability (118.5 mg/g). Several mechanisms control MB adsorption by the DSRPAC, including electrostatic forces, π–π stacking, and H-bonding. This work shows that DSRPAC derived from DS and RP could serve as a viable adsorbent for the treatment of industrial effluents containing organic dye. The novelty of this research work comes from the conversion of the mixed biomass wastes from tropical fruit including durian seeds and rambutan peels as precursor for activated carbon (DSRPAC) using microwave assisted H3PO4 activation. The effectiveness of DSRPAC as promising adsorbent was tested for methylene blue (MB) dye adsorption. Furthermore, response surface methodology with Box Behnken design (RSM-BBD) was applied to optimize the adsorption key parameters. A tailored adsorption mechanism of MB on the surface of DSRPAC was proposed. [ABSTRACT FROM AUTHOR]

Extensive research has demonstrated the advantageous utilization of medium–low temperature fast pyrolysis (FP) for biomass, yielding high–grade liquid–phase chemicals or fuels. However, the field of FP–based high–performance solid biochar research still presents several gaps. Herein, a one–step versus two–step method for biomass H3PO4 activation under FP was comparatively analyzed for the first time, and efficiently activated carbons (ACs) for dye removal were successfully synthesized at a low temperature (723 K). Investigation of methylene blue (MB) adsorption revealed that the one–step sample P–H–0.5, possessing a specific surface area of 1004 m2·g−1, exhibited a remarkable adsorption capacity of 695.54 mg·g−1 with an ultra–high removal rate (99.94%, C0 = 150 mg·L−1). The two–step sample P–2–H–2, a modified byproduct of FP, achieved efficient dye adsorption in the shortest time (2 min, 383.91 mg·g−1). This originated from the well–developed surface macropores and elevated group content derived from phosphorus (P)—modification. Both adsorption data were well–fitted with pseudo–second–order kinetics and the Langmuir model, revealing the presence of chemical effects and the dominance of monolayer adsorption. A more detailed kinetic study suggested intrapore transport primarily governed the adsorption process on P–H–0.5, whereas P–2–H–2 relied on surface diffusion. FTIR and XPS revealed notable differences in the active sites between the two methods. Aside from –OH, –COOH with C–O–P, the P elements of P–H–0.5 were classified as C–P–O3 and C2–O–P2, demonstrating the ability of one–step FP to introduce heteroatoms into carbon defects. The basic interactions of ACs with MB were π–π stacking and hydrogen bonding established by –OH–containing groups. At a suitable pH (>5), most H+ was removed from the surface, and the electrostatic attraction became the strongest linking force. Both ACs exhibited exceptional reusability, with removal rates surpassing 90% of the initial rate after four cycles of regeneration. [ABSTRACT FROM AUTHOR]

A porous biochar was manufactured through the valorization of waste pork bones, following a three-step process including pre-charring under mild conditions, acid treatment and thermal activation. The influence of the acid (H2SO4 and H3PO4) and the impregnation ratio on the physicochemical properties of the material was investigated. Acid treatment at 0.2 mmolacid/gprecursor increased BET area by about 80%, compared to untreated bone char. When using H2SO4, higher impregnation ratios significantly enhanced microporosity (up to 263%). This increased microporosity should be associated to a specific reaction mechanism of H2SO4 with a source of carbon. On the contrary, the higher activity of H3P04 led to a dramatic removal of porosity for large impregnation ratios (about 20mmol/g). The acid activation mechanism involves the formation of cation-deficient HAp, which is thereafter decomposed upon thermal treatment. The maximum uptake of methylene blue was achieved at low impregnation ratios (0.2 and 1.0mmol/g), and could be related to surface area corresponding to large micropores and small mesopores. [ABSTRACT FROM AUTHOR]

Abstract: Seed hulls (or coats) of peanut, soybean, cottonseed, lupine, broad beans, and sunflower seeds, were subjected to various treatments in order to get adsorbing carbons. Characterization of porosity was determined by N2/77K adsorption isotherms. Simple pyrolysis at 500°C yields low adsorbing carbons of meso-/macroporous character, whereas steam activation of these chars at 850°C enhances porosity, in micropores, to a limited extent. Chemical activation with H3PO4 at 500°C exerts the best recommending influence in producing high adsorbing carbons with evenly distributed porosity within micro-mesopore ranges. It was found that phosphoric acid activation of the studied precursors enhanced the yield, surface area and pore volume; 32–46%, 437–1022m2/g and 0.444–0.809, respectively, as compared to other treatments. The capacity to remove methylene blue, in single bottle experiments, complements the state of porosity deduced from the gas phase adsorption of N2. Peanut shells proved the best feasible raw material under all treatment processes, whereas lupine seeds and sunflower seed hulls show relatively the least affected. Dye removal capacity was enhanced by carbon mesoporosity, whereas adversely affected by its increased surface pH and ash content was observed. Low-cost by-products of oil producing industry seem, thus, to be promising precursors for the production of highly valuable adsorbing carbons. [Copyright &y& Elsevier]

Abstract: Highly mesoporous activated carbons (ACs) with a mesopore fraction ranging from 42 to 73% were obtained by activation of rice straw (RS) with ortho-phosphoric acid (PA). Due to such a high mesoporosity, these ACs can be successfully used for pollutant removal in aqueous phase. The ACs were prepared at activation temperatures (T) ranging from 350 to 500°C, using PA to RS weight ratios (R) from 0 to 1.6 and activation times from 0 to 2h. They were characterised by nitrogen adsorption at −196°C, SEM-EDX, and methylene blue adsorption. RS is a very heterogeneous material with a variable content of mineral matter: using the product of activated carbon yield multiplied by surface area (C × S BET ) as the performance criterion, the best AC was produced at T =450°C and R ≥1. These conditions lead to S BET higher than 500m2 g−1 and a C × S BET around 270m2 g−1. [Copyright &y& Elsevier]