Performance of Pleurotus ostreatus Mushrooms and Spent Substrate for the Biosorption of Cd(II) From Aqueous Solution

Removal of lead ions in an aqueous solution by living and modified Aspergillus niger

An indigenous lead-tolerant fungal strain was isolated from lead-contaminated soil and identified as Aspergillus niger, via 18S rRNA gene sequencing. We determined the adsorption and accumulation of Pb(II) by living A. niger and the adsorption of Pb(II) via modified A. niger. This strain resisted and removed 96.21%-100% Pb(II) ranging from 2 to 8 mmol/L Pb(II). Pb-containing particles were observed outside of the cell, and lead was detected inside the cell under scanning electron microscopy and transmission electron microscopy. The process of measuring the adsorption ability of modified fungal biomass, freeze-dried, high-temperature, and alkali-treated fungal samples was analyzed; they adsorbed 25.02%, 8.76%, and 15.05% Pb(II) under 8 mmol/L Pb(II) in 43, 10, and 10 hr, respectively. These three types of modified A. niger fit the pseudo-second-order model equation well. PRACTITIONER POINTS: Isolation and identification of effective Pb(II) removal strain from the soil around Dexing lead-zinc mine. The ability of living and modified Aspergillus niger to remove Pb(II) in an aqueous environment was evaluated. Lead distributions inside and outside the cell were analyzed by SEM and TEM. Kinetic models for modified biomass adsorbing Pb(II) were made for describing adsorption process.

Spent mushroom substrate combined with alkaline amendment passivates cadmium and improves soil property

As an extremely toxic metal, cadmium (Cd) is readily taken up by most plants. In situ Cd passivation is of great importance to reduce Cd availability in soil. In this experiment, two alkaline amendments, lime (L) (at a dosage of 0.02%, 0.04%, or 0.08%) and biochar (B) (at a dosage of 0.5%, 1%, or 2%), were used to improve Cd passivation by spent mushroom substrate (SMS) in a simulating Cd-contaminated soil (0.6 mg kg^-1). Results showed that the application of SMS alone reduced Cd bioavailability by 44.80% and EC by 9.71% and increased soil pH by 0.61 units, CEC by 25.32%, and soil enzymes activities by 17.11% to 21.10% compared with non-amendment Cd-contaminated soil. Biochar combination enhanced the efficiency of SMS on Cd reduction by 48.32-66.58% and pH increased by 0.17 to 0.59 units and enzymes activities elevation by 5.74% to 47.29% in a dose-dependent manner. Lime also facilitated SMS to passivate Cd by decreasing bioavailable Cd by 63.10%-66.47% and increasing soil pH by 0.25-0.72 units and enzymes activities by 3.28% to 37.86% compared to those of SMS. Among six combined amendments, SMSB3 (0.5% SMS + 2% B) performed best in reducing bioavailable Cd (39.46% higher than SMS), increasing organic matter content (28.54% higher than SMS) and soil enzyme activities (25.82%, 47.29%, and 26.23% higher than that of SMS for catalase, urease, and invertase, respectively). Both biochar and lime can assist SMS to passivate Cd and improve soil property, and biochar is more efficient than lime in reducing cadmium content and increasing enzyme activity and organic matter.