Biosorption mechanism of Zn2+ from aqueous solution by spent substrates of pleurotus ostreatus

Expanding the valorization of waste mushroom substrates in agricultural production: progress and challenges

Waste mushroom substrate (WMS) generated in large quantities from mushroom production process has caused severe environmental pollution. As a sustainable resource, the valorization of WMS in the agricultural field has attracted attention due to the abundant active components. A comprehensive review of valorization of WMS in agricultural production is meaningful to promote the further utilization of this resource. This paper provided an overview of the valorization in sustainable agricultural production using WMS, including animal and crop farming improvement, and agricultural environmental restoration. Moreover, the limitations and the possible development directions of WMS in agricultural production were discussed. Different sustainable cycle models for WMS in agricultural production were proposed. The aim of this review is to provide a feasible solution for the favorable treatment of WMS and improvement of agricultural production quality.

Characterization of biochars derived from various spent mushroom substrates and evaluation of their adsorption performance of Cu(II) ions from aqueous solution

A total of 16 biochar adsorbents were produced from four types of spent mushroom substrates to investigate the effect of pyrolysis temperature and raw material composition on the Cu(II) adsorption performance of the resulting biochars. It was determined that the pyrolysis temperature and substrate composition markedly influenced the thermal stability, the degree of carbonization, surface functional group content, and structural morphology of the biochars, but did not affect the adsorption isotherms or kinetics. Optimal results were obtained with an initial pH of 5, adsorbent dosage of 1 g/L, Cu(II) concentration of 50 mg/L, and temperature of 25 °C. The four best-performing biochars conformed to the Langmuir isotherm model and followed pseudo-second-order kinetics with maximum Cu(II) adsorption between 52.6 and 65.6 mg/g. Precipitation was the dominant mechanism for Cu(II) adsorption onto Lentinus edodes spent substrate-derived biochar pyrolyzed at 600 °C (LESS600), whereas complexation with surface functional groups was the prominent mechanism of Cu(II) removal by Auricularia auricula spent substrate-derived biochar pyrolyzed at 500 °C (AASS500). The Flammulina velutipes and Pleurotus ostreatus spent substrate-derived biochars pyrolyzed at 600 °C (FVSS600 and POSS600, respectively) removed Cu(II) ions using both precipitation and Cu²⁺-π complexation interactions. The findings indicate that biochar derived from spent mushroom substrates containing abundant lignin and pyrolyzed at high temperatures (500 or 600 °C) demonstrate effective Cu(II) removal because of the various physico-chemical properties discussed herein.

Anaerobically fermented spent mushroom substrates improve nitrogen removal and lead (II) adsorption

In this study, spent mushroom substrates (SMSs) were fermented anaerobically at room temperature to gain liquid SMSs (LSMSs) that were used to remove nitrogen from the piggery wastewater with a low C/N ratio in a sequencing batch reactor (SBR) and solid SMSs (SSMSs) that were utilized to adsorb Pb²⁺ from Pb²⁺-containing wastewater in a fixed-bed reactor (FBR). After LSMSs supplement, the removal efficiency of both total nitrogen (TN) and NH⁺₄-N increased from around 50% to 60-80%. High-throughput sequencing results presented an obvious change in microbial diversity, and some functional microorganisms like Zoogloea and Hydrogenophaga predominated to promote nitrogen removal. Pb²⁺ did not emerge from the effluent until 240 min with the corresponding concentration being less than 3 mg/L when using 30-day SSMSs as adsorbents, and it was demonstrated to be appropriate to use the Thomas model to predict Pb²⁺ sorption on SSMSs. Although various functional groups played a role in binding ions, the carboxyl group was proved to contribute most to Pb²⁺ adsorption. These results certified that the anaerobically fermented SMSs are decidedly suitable for wastewater treatment.

A meta-analysis of metal biosorption by suspended bacteria from three phyla

Biosorption of heavy metals by bacterial biomass has been the subject of significant research interest in last decades due to its efficiency, relatively low cost and minimal negative effects for the surrounding environment. In this meta-analysis, the biosorption efficiencies of different bacterial strains for Cu(II), Cd(II), Zn(II), Cr(III), Mn(II), Pb(II) and Ni(II) were evaluated. Optimum conditions for the biosorption process such as initial metal concentration, temperature, pH, contact time, metal type, biomass dosage and bacterial phyla, were evaluated for each heavy metal. According to the results, the efficiencies of bacterial biomass for removal of heavy metal were as follows: Cd(II) > Cr(III) > Pb(II) > Zn(II) > Cu(II) > Ni(II) > Mn(II). Firmicute phyla showed the highest overall (living and dead) biosorption efficiency for heavy metals. Living biomass of Proteobacteria had the best biosorption performance. Living bacterial biomass was significantly more efficient in biosorption of Cu(II), Zn(II) and Pb(II) than dead biomass. The maximum biosorption efficiency of bacterial strains for Cd(II), Pb(II) and Zn(II) was achieved at pH values between 6 and 7.5. High temperatures (>35 °C) reduced the removal efficiencies for Cu(II) and Zn(II) and increased the efficiencies for Cd(II) and Cr(III) ions. The maximum biosorption efficiency of non-essential heavy metals occurred with short contact times (<2 h). Essential metals such as Zn and Cu were more efficiently removed with long biosorption durations (>24 h). The mean biosorption capacity of bacterial biomass was between 71.26 and 125.88 mg g^-1. No publication bias existed according to Egger's and Begg's test results.

Impact of spent mushroom substrate on Cd immobilization and soil property

This study aims to evaluate the potential of fresh spent mushroom substrate (SMS) in Cd immobilization and soil improvement, compared with spent mushroom substrate biochar (SMSB) and spent mushroom substrate compost (SMSC). A simulating remediation experiment was conducted with soil at Cd concentration of 0.6, 1.2, 1.8, and 2.4 mg kg^-1 and amendment addition ratio of 0.5%, 1%, 2%, and 4% for 90 days. At the end of incubation, it was found that 4%SMS addition showed the best effect both on Cd immobilization and soil improvement. It decreased Cd exchangeable fraction ratio by 52.77% (16.30% higher than 4%SMSC) and increased residual fraction ratio by 65.28% (36.34% and 49.64% higher than 4%SMSB and 4%SMSC, respectively); increased soil pH, EC, and CEC by 10.43% (3.83% higher than 4%SMSC), 11.54%, and 29.72%; and increased urease activity, sucrase activity, and catalase activity by 125.61% (43.90% and 8.54% higher than 4%SMSB and 4%SMSC, respectively), 79.46% (35.35% and 14.02% higher than 4%SMSB and 4%SMSC, respectively), and 75.68% (29.73% higher than 4%SMSB), compared with control treatment (CK) respectively. The results demonstrate that 4%SMS can be used as amendments for cadmium-contaminated soils.

Two physical processes enhanced the performance of Auricularia auricula dreg in Cd(II) adsorption: composting and pyrolysis

This study aims to discover the impact of composting and pyrolysis on the adsorption performance of Auricularia auricula dreg (AAD) for Cd(II) in aqueous solution. Auricularia auricula dreg (AAD), Auricularia auricula dreg biochar (AADB) and Auricularia auricula dreg compost (AADC) were used to remove Cd(II) from aqueous solution, and their adsorption conditions and mechanisms were compared. The adsorption quantity of three adsorbents reached the maximum (AAD: 80.0 mg/g, AADB: 91.7 mg/g, AADC: 93.5 mg/g) under same conditions (adsorbent dosage of 1 g/L, pH 5.0, biosorption temperature of 25 °C, and biosorption time of 120 min). All Cd(II) biosorption processes onto three adsorbents complied with the Langmuir isotherm model and the pseudo-second-order kinetic equation, and spontaneously occurred in an order of AADC > AADB > AAD. The difference in biosorption quantity relied on variation in surface structure, crystal species and element content caused by composting or pyrolysis. Composting enhanced the changes in surface structure, crystal species, functional groups and ion exchange capacity of the AAD, resulting in AAD had greatly improved the biosorption quantity of Cd(II). Pyrolysis increased the adsorption of Cd(II) mainly by increasing the Brunauer-Emmett-Teller (BET) surface area, the particle size and pH, in the same time, providing more oxygen-containing functional groups.

Batch and fixed-bed biosorption of Cd(II) from aqueous solution using immobilized Pleurotus ostreatus spent substrate

To prevent the blockage in a continuous fix-bed system, Pleurotus Ostreatus spent substrate (POSS), a composite agricultural waste, was immobilized into granular adsorbents (IPOSS) with polymeric matrix, and used to remove Cd(II) from synthetic wastewater in batch experiment as well as in continuous fixed-bed column system. In batch experiment, higher pH, temperature and Cd(II) initial concentration were conducive to a higher biosorption capacity, and the maximum biosorption capacity reached up to 87.2 mg/g at Cd(II) initial concentration of 200 mg/L, pH 6 and 25 °C. The biosorption of Cd(II) onto IPOSS followed the Langmuir isotherm model with the maximum adsorption capacity(q_max) of 100 mg/g. The biosorption was an endothermic reaction and a spontaneous process based on positive value of ΔH⁰ and negative value of ΔG⁰. In fixed-bed column system, higher bed depth, lower flow rate and influent Cd(II) concentration led to a longer breakthrough and exhaustion time, and the best performance (equilibrium uptake (q_e) of 14.4 mg, breakthrough time at 31 h and exhaustion time at 78 h) was achieved at a bed depth of 110 cm, a flow rate of 1.2 L/h and an influent concentration of 100 mg/L. Furthermore, regeneration experiment revealed a good reusability of IPOSS with 0.1 M HNO₃ as eluting agent during three cycles of adsorption and desorption. Cd(II) biosorption onto IPOSS mainly relied on a chemical process including ion exchange and complexation or coordination revealed by SEM-EDX, FTIR and XRD analysis.