Search Results (4)

One of the most widely employed methods for adsorption is the utilization of biochar produced during pyrolysis. Biochar has attracted considerable attention due to its oxygen-containing functional groups and relatively high specific surface area. In alignment with the principles of cleaner production, the sludge generated from sewage treatment plants is typically classified as waste. However, it can be effectively repurposed as an adsorbent following pyrolysis and subsequent nanoparticle modification. This environmentally friendly approach presents an ecological alternative to conventional water treatment methods. The objective of this study is to evaluate the efficiency of batch adsorption for the removal of phosphate from wastewater using both unmodified and modified sewage sludge biochars (SSBs) that were produced at various temperatures (300 °C, 400 °C, 500 °C, and 600 °C) and modified with zero-valent iron nanoparticles (nZVI-SSB300, nZVI-SSB400, nZVI-SSB500, and nZVI-SSB600). The findings indicate that biochar modified with functional nanoparticles is a highly effective adsorbent for the removal of phosphate from wastewater. As demonstrated by the research results, the adsorption capacity of modified biochar is approximately 3 to 3.5 times greater than that of the unmodified variants. The phosphate removal efficiency with modified biochars was optimal with nZVI-SSB600. In experiments with a phosphate concentration (25 mg/L), the modified sorbent biochar exhibited an equilibrium adsorption capacity of 23.74 mg/g, translating to a phosphate removal efficiency of 60%. Under similar test conditions, at an initial phosphate concentration of 50 mg/L, the adsorption capacity improved to 25.67 mg/g (75% efficiency); at 75 mg/L, it reached 27.97 mg/g (80%); at 100 mg/L, it was 28.44 mg/g (85%); and at 125 mg/L, it achieved 29.48 mg/g (89%). The models confirmed the observed adsorption behavior, yielding a maximum phosphate adsorption capacity (q_e) of 19.00 mg/g for the 600 °C pyrolysis of modified biochar at the primary phosphate concentration (25 mg/L). Furthermore, this study indicates that the influence of solution pH on phosphate adsorption remains stable and maximal (nZVI-SSB600, ranging from 16.87 to 20.46 mg/g) within the pH range of 3 to 8. On average, the modified biochar (nZVI-SSB) demonstrated 20 to 30% superior adsorption performance compared to the unmodified biochar (SSB). Additionally, significant differences were noted between various ambient temperatures, ranging from 5 °C to 25 °C. As the ambient temperature increased, the sorption capacity of the adsorbent exhibited a considerable improvement. With a primary concentration of phosphate (100 mg/g) at 5 °C, the adsorption capacity of nZVI-SSB600 was measured at 7.99 mg/g; this increased to 14.33 mg/g at 10 °C, 21.79 mg/g at 20 °C, and 28.44 mg/g at 25 °C. This research highlights the potential application of biochar in wastewater treatment for phosphate removal, simultaneously enabling the effective utilization of generated sewage sludge waste through pyrolysis and coating with zero-iron nanoparticles, resulting in a sustainable solution. Full article

Three types of modified sludge biochar were produced for the adsorption of copper in aqueous solutions via the calcium-based magnetic (CaCO₃, Feⁿ⁺) treatment (CA–BC), nanozero-valent iron (nZVI) treatment (nZVI–BC), and iron (Fe³⁺) treatment (FA–BC) of raw biochar. The results suggested that the adsorption capacity for Cu²⁺ of calcium-based magnetic attapulgite/sludge biochar (CA–BC) prepared from CaCO₃, FeCl₃, and FeSO₄ is 38.01% greater than that of unmodified biochar and 6.41% to 17.5% greater than that of the other biochar. The CA-BC contained a variety of ferrite-containing and hydroxide-functional groups, as well as a more developed pore structure. The existence of H⁺ reduced the adsorption capacity of the biochar for Cu²⁺. A high initial concentration of Cu²⁺ could increase Cu²⁺ adsorption on CA–BC. Combined with theoretical calculations, the adsorption efficiency of CA–BC in different systems was explored. The results revealed that CA–BC achieved a maximum removal rate of 92.644% at a pH of 6 with a reaction time of 157 min and an initial Cu²⁺ concentration of 2.813 mg/L. These results suggest that CA–BC shows great potential for removing Cu²⁺ from aqueous solutions. Full article

Antibiotics are prescribed in human and veterinary medicine for the treatment of infectious diseases. They are also widely used for animal farming, aquaculture and agriculture. Antibiotics are not fully absorbed and metabolized and are therefore, often excreted unmodified. As sewage plants are not equipped to remove these drugs from wastewater, antibiotics may be discharged into the environment and reach the soil in many ways. The pharmaceutical industry, hospital and municipal wastewater containing antibiotics may be used for irrigation and animal manure, whilst sewage sludge and biosolids are frequently used as fertilizers for agricultural lands. This allows antibiotics to contaminate soil, ground water and the entire food chain. The major concern about antibiotics in the environment is their contribution to the resistance development in human and animal pathogens that can lead to a serious threat to human health. There are several procedures that determine the fate of antibiotics in soil such as transport, leaching, plant uptake, photodegradation, biodegradation and adsorption. The adsorption of these drugs into the soil depends on its physico-chemical characteristics (Cation Exchange Capacity, pH, permeability, iron oxide content, etc.), texture, organic matter and climate conditions. However, the assessment of the literature shows that more studies need to be carried out on the occurrence, fate and risks associated with antibiotics in the soil. For this purpose, the adsorption of an antibiotic widely used in human and veterinary medicine (amoxicillin) in an agricultural soil was studied. This experimental study was carried out in order to investigate the influence of several parameters: the contact time, the initial antibiotic concentration, the pH and the temperature on the contamination risk of soil by adsorption. These experiments showed that the adsorption of amoxicillin in soil is rapid. For a liquid/solid ratio of 10 L/kg and an initial antibiotic concentration of 10 ppm, the adsorption equilibrium was reached within 20 minutes and the maximum amount of amoxicillin adsorbed was of 23 mg/kg. The adsorption kinetics were well described by the pseudo-first-order model and exhibited a three-stage intra-particle diffusion mode. The adsorption capacity of soil increased with the initial antibiotic concentration (from 10 to 100 ppm) and the relative adsorption isotherm (type II) was in accordance with the Guggenheim-Anderson-deBroer model. The adsorption of amoxicillin was improved in the acidic medium. The thermodynamic study showed that the adsorption of amoxicillin in soil was a physical process. The overall study shows that amoxicillin is a potential contaminant for soil. Full article

Arsenic and heavy-metal-contaminated environments are a major concern due to their negative impacts on exposed people and ecosystems. In this study, sludge from an iron-ore processing area was used as an adsorbent to remove As, Mn, Zn, Cd, and Pb from aqueous solutions. The adsorption capacity of target adsorbates was investigated in batch experiments of both single- and mixed-metal solutions. The batch studies show that the maximum Langmuir adsorption capacities of the heavy metals onto the adsorbent occurred in the order Pb > As > Cd > Zn > Mn, and ranged from 0.710 mg/g to 1.113 mg/g in the single-metal solutions and from 0.370 mg/g to 1.059 mg/g in the mixed-metal solutions. The results of the kinetic experiments are consistent with pseudo-first-order and pseudo-second-order models, with a slightly better fit to the latter. Adsorption performances indicate that iron-ore sludge can simultaneously adsorb multiple metal ions and is a promising adsorbent for the removal of toxic pollutants from water. Full article