Toxic metals and the risks of sludge from the treatment of wastewater from beryllium smelting

Potential amendments of coal fly ash-derived zeolite to beryllium contaminated soil at a legacy waste disposal site

Management of Be contamination using industrial solid waste or solid waste-derived amendments is not well understood. This study investigated the potential of Australian coal fly ash (CFA), derived synthesized zeolite (SynZ) and chitosan-modified zeolite (ModZ), for Be immobilization at the Little Forest Legacy Waste Site (LFLS), a low-level radioactive waste disposal site near Sydney, Australia. In laboratory simulation experiments, the SynZ and ModZ were separately applied as an amendment to both naturally contaminated soil and simulated contaminated (spiked) soil. Different techniques, including pore water (PW), batch desorption, and microbial activities were assessed to provide insight into immobilization mechanisms. Results revealed that amendment of 2% ModZ in soils, substantially decreased Be concentrations in PW (PWBe) ranging from 13.3% to 99.5% across all concentrations of Be. In contrast, PWBe increased while using SynZ, which could be attributed to the increased solubility of different organic-inorganic elements in PW. Moreover, batch desorption using Milli-Q water, simulated acid rainwater [H2SO4/HNO3 = 60/40, (v/v), and 0.11 M acetic acid solution also revealed similar patterns of Be immobilization as found in PWBe analysis. Soil amendments boosted microbial biomass carbon, and phosphorous (MBC,P), along with basal respiration (BRCO2). This indicates increased microbial activities, which are linked with environmental eco-friendliness. This effect was substantially noticed in ModZ-amended soils, exhibiting up to 22 times higher in BRCO2 values compared to unamended soil. Additionally, reduced PWBe was correlated with soluble organic-inorganic elements, desorbed Be in the batch study, and soil MBc. The differences in behavior between SynZ and ModZ underline the importance of carefully studying the various potential amendment materials and the need to evaluate their performance before application in field situations. This study highlights ModZ's effectiveness in eco-friendly Be immobilization, underlining the role of organic functional groups in zeolite architecture, a key factor in controlling Be in soils.

Leaching behavior and kinetics of beryllium in beryllium-containing sludge (BCS)

Beryllium-containing sludge (BCS) is a byproduct of the physicochemical treatment of beryllium smelting wastewater. The pollutant element beryllium within BCS is highly unstable and extremely toxic, characterized by its small ionic radius and low charge density, resulting in a high risk of leaching and migration. This study is the first to investigate the leaching behavior, influencing mechanisms, and kinetic processes of beryllium in BCS under various environmental conditions. The results indicate that, under national standard conditions, beryllium exhibits a rapid leaching phase within the first 5 h, which then stabilizes after 10 h, with the total leached content significantly exceeding the leaching toxicity identification standards. Under mildly acidic (pH ≤ 5) or highly alkaline (pH = 14) conditions, beryllium demonstrates pronounced leaching and migration behaviors. Notably, in acidic conditions, the leaching rate exceeds 80% within 5 h. Combining the treatment process of beryllium-containing wastewater with analytical methods such as SEM, XPS, ToF-SIMS, and FTIR, it is revealed that due to the heterogeneous nature of BCS, the particle aggregates dissociate over time under acidic conditions. The particle surfaces become increasingly rough, leading to dissolution and the emergence of more reactive sites, resulting in a high proportion of beryllium leaching. Under these conditions, the gradual reaction of Be(OH)2 in BCS to form soluble Be2+ and its hydrolytic complexes is identified as the primary mechanism for extensive beryllium migration. The process encounters minimal diffusion resistance and is classified as reaction-controlled. In acidic conditions with pH = 4, the leaching rate of beryllium significantly increases with rising temperature. The leaching kinetics equation is [(1-x)-0.44]=e(18.26-53050RT)·t, with an apparent activation energy of 53.05 kJ mol-1.

An eco-friendly porous hydrogel adsorbent based on dextran/phosphate/amino for efficient removal of Be(II) from aqueous solution

A novel environmentally-friendly porous hydrogel adsorbent (GHPN) is firstly designed and prepared using dextran, phosphate, and calcium hydroxide for the adsorption of Be(II). GHPN shows good adsorption selectivity for Be(II) (Kd = 1.53 × 104 mL/g). According the adsorption kinetics and thermodynamics, the theoretical adsorption capacity of GHPN to Be(II) is 43.75 mg/g (35 °C, pH = 6.5), indicating a spontaneous exothermic reaction. After being reused for 5 cycles, the adsorption and desorption efficiencies of Be(II) with GHPN are obtained to be more than 80 %, showing acceptable recycling performance. Both of the characterizations and theoretical calculations indicate that the phosphate group, hydroxyl group, and amino group own the affinity to form stable complexes with Be(II). Benefiting from the introduction of phosphate and amino, the adsorption effect of the hydrogel adsorbent on Be(II) can be greatly improved, and surface precipitation, complexation, and ligand exchange are the dominant mechanisms of beryllium adsorption. The results suggest that GHPN has great potential to be utilized as an eco-friendly and useful adsorbent of Be(II) from aqueous solution.

Porous durian shell biochar modified by KMnO4 (Mn-DSB) as a highly selective adsorbent for Be(II)

The mining of uranium-beryllium ores has resulted in substantial beryllium (Be) contamination. In this study, agricultural waste durian shells were utilized as raw materials to prepare biochar, which was further modified to enhance its adsorption capacity (Mn-DSB). The results effectively demonstrated Mn loading onto the DSB surface. Batch experiments were conducted to identify the optimal adsorption conditions of Mn-DSB for beryllium. At a temperature of 35 °C and pH 6, beryllium's maximum adsorption capacity (Qe) was 42.08 mg·g-1. The materials' internal structure was analyzed before and after adsorption via multiple techniques. Mn-DSB manifested potent selectivity towards beryllium in multicomponent mixed solutions, binary systems, and uranium-beryllium wastewater, as the beryllium removal rate exceeded 90%. The study investigated the recyclability of Mn-DSB and found that after five reuse cycles, the adsorption and desorption efficiencies were 90% and 85%, respectively. The strong ligand complexation (N-H, CO32-, -OH) and ion exchange mechanisms (with Mn7+ ions) of Mn-DSB explained its high adsorption capacity. Therefore, this study demonstrates the potential of Mn-DSB for treating uranium-beryllium tailing wastewater.