Removal of Arsenic from Wastewater Using Hydrochar Prepared from Red Macroalgae: Investigating Its Adsorption Efficiency and Mechanism

Abstract

Arsenic (As) is a prominent carcinogen component produced via both geogenic and anthropogenic processes, posing serious risks to human health. This study aimed to investigate the potential of hydrochar prepared from red macroalgae for removing As from synthetic wastewater. The hydrochar was produced through 5 h hydrothermal carbonization (HTC) treatment at 200 °C, and then, chemically activated with ferric chloride hexahydrate (FeCl3·6H2O). SEM analysis revealed a permeable structure of hydrochar, while FTIR analysis detected the occurrence of several functional groups at the hydrochar interface. EDS analysis showed an increase in carbon concentration after FeCl3·6H2O activation. Hydrochar was then tested in batch experiments to investigate its As removal efficiency, with ICP-MS used to determine the levels of As after the adsorption process. The results showed that As removal efficiency increased with increasing initial As concentration from 50 to 250 mg/L, and the highest As removal efficiency was 84.75% at a pH of 6, initial concentration of 0.25 mg/L, and adsorbent dose of 1000 mg at 120 min. The Langmuir isotherm model supported the occurrence of homogeneous adsorption over the surface of hydrochar, while the pseudo-second-order model confirmed the chemisorptive nature of the process.

Adsorption of Arsenic From Aqueous Solution Using Brown Seaweed (Sargassum Polycystum) Derived Biochar Impregnated With Iron Oxide (Fe2o3): Batch and Column Studies Modelling

“…When more biochar is added to the solution, the number of active sites also increases, providing more opportunities for arsenic to be adsorbed onto the biochar (Nguyen et al 2019). These results are consistent with the findings of (Khanzada et al 2023).…”

“…Fig 3 . illustrates that the arsenic adsorption efficiency improved from 60% to 88% with the increasing of pH from 2 to 6 and decreased from 88% to 66% with the increasing of pH from 6 to 10. This trend of increasing adsorption efficiency at pH 6 was consistent with previous investigations carried out by (Poo et al 2018;Khanzada et al 2023), who also found that the optimal pH for arsenic removal was around 6-8, and the most efficient removal occurred at pH 6. Additionally, the current investigation revealed that the binding of metal ions is influenced by the pH levels and the surface groups present on the adsorbent (Rahmani and Amini 2016).…”

“…Furthermore, the oxygen percentage was decreased, and carbon and iron percentages were increased with iron modification which confirms the impregnation of iron oxide particles on biochar surface (Ren et al 2015). However, after the modification of biochar, the percentages of potassium, sodium, aluminum, calcium, phosphorous, silicon and magnesium were also reduced as previously noted by (Khanzada et al 2023).…”

“…However, a promising area of research involves using naturally occurring waste and readily available materials such as marine seaweed or macroalgae as adsorbents. Marine seaweed, in their natural form, has demonstrated remarkable abilities to remove cationic metal species from solutions (Khanzada et al 2023). A wide variety of algae species, collectively referred to as "Seaweed/Macroalgae," can be found in water bodies like oceans, lakes, and rivers.…”

Nanoparticles in Soil Remediation: Challenges and Opportunities

“…Sebastian et al [48] have reported that heavy metals like Cd and As can be effectively absorbed and immobilised by Fe3O4. However, in the absence of surface modification with stabilising agents like starch or carboxymethyl cellulose, Fe3O4 particles tend to agglomerate and trapped among soil particles [49]. Overall, this application aligns with Sustainable Development Goal 15: Life on Land, which emphasizes the need to protect, restore, and promote sustainable use of terrestrial ecosystems, including addressing land degradation and combating desertification.…”