Comparative study by microwave pyrolysis and conventional pyrolysis of pharmaceutical sludge: Resourceful disposal and antibiotic adsorption

Compared with conventional pyrolysis, microwave pyrolysis has superior heat transfer performance and promotes the decomposition of organic matter. The paper focuses on the harmless treatment and resource utilization of pharmaceutical sludge (PS) by microwave heating and conventional heating methods. The experimental results showed that the conventional pyrolysis gas is dominated by CO2, CO and H2. For microwave pyrolysis gas, the "microwave effect" promoted secondary cracking of volatile fractions and increases the content of CH4, CxHy, H2 and CO through condensation, aromatization, and dehydrogenation. Conventional pyrolysis oils contained the highest percentage of oxygenated compounds. However, high-temperature microwave radiation accelerated the cleavage of polar oxygenated molecular bonds and long-chain hydrocarbons, thereby increasing the aromatics content of pyrolysis oils. The solid residues obtained from microwave pyrolysis is highly graphitized and porous, with a surface area of 146.2 m2/g. Furthermore, the solid residue was rich in pyridine-N and pyrrole-N that could be utilized for adsorption and catalysis. The MA-600 removes up to 99% of tetracycline (TC) in 6 h. It was also found that the adsorption process of TC by the two pyrolysis residues was consistent with the proposed secondary and Freundlich models.

Treatment of industrial ferric sludge through a facile acid-assisted hydrothermal reaction: Focusing on dry mass reduction and hydrochar recyclability performance

Large amounts of Fenton sludge and waste activated sludge (WAS) are mixed as ferric sludge (FS) in most industrial wastewater treatment plants. The treatment of such waste represents a challenge and quantity-dependent cost, so that a reliable way for FS waste reduction is required. In this study, we develop a facile acid-assisted hydrothermal treatment (HT) for the cost-efficient treatment of hazardous FS waste. Sulfuric acid was dosed at 0.25 mL/g dry solid (DS) to the HT process, which significantly increased the total solid mass reduction (TMR) by 25.1 % and dry mass reduction (DMR) by 104.4 %. The participation of sulfuric acid during the HT process changed the HT reaction pathway from dehydration to demethylation based on the analysis of the derivative thermogravimetric and Van Krevelen diagram. The addition of sulfuric acid improved the release of Fe from FS by 52.9 %, which contributed to the DMR. During the acid-assisted HT, Fe(III) was effectively reduced to Fe(II) within the produced hydrochar, which can be recycled for the Fenton reaction during the degradation of actual industrial wastewater such as pharmaceutical wastewater. Moreover, Sulfuric acid facilitated the generation of sulfonated hydrochar, which was efficient as an adsorbent for the complete removal of some metals such as Cu(II) - cation metal (98.8 %) and Cr(VI) - anion metal (99.9 %). This study firstly provides a novel and reliable approach for hazardous FS reduction and pointed out the recycling of hydrochar as the supplement for the Fenton reaction and adsorbents for some hazardous heavy metals.

Pyrolysis temperature-switchable Fe-N sites in pharmaceutical sludge biochar toward peroxymonosulfate activation for efficient pollutants degradation

Pyrolysis of pharmaceutical sludge (PS) is a promising way of safe disposal and to recover energy and resources from waste. The resulting PS biochar (PSBC) is often used as adsorbent, but has seldom been explored as catalyst. Herein we demonstrate that PSBC (0.4 g/L) could efficiently activate peroxymonosulfate (PMS) to 100% degrade 4-chlorophenol (4-CP) with rate constants of 0.42-1.70 min^-1, outperforming other reported catalysts. Interestingly, the PMS activation pathway highly depended on PSBC pyrolysis temperature, which produced dominantly high-valent iron species (e.g., Fe^IVO²⁺) at low temperature but more sulfate radical (SO₄^·-) and hydroxyl radical (·OH) at higher temperature, e.g., 0.17, 0.23, 0.12 mmol/L of Fe^IVO²⁺ and 0.009, 0.038, 0.102 mmol/L of SO₄^·-/·OH were produced within 10 min by PSBC-600/PMS, PSBC-800/PMS, and PSBC-1000/PMS, respectively. Characterization, density functional theory (DFT) simulation and Pearson correlation analysis revealed that along with the increase of pyrolysis temperatures, the active sites of PSBC gradually shifted from atomically dispersed N-coordinated Fe moieties (FeN_x) to iron nitrides (Fe_xN), which activated PMS to produce Fe^IVO²⁺ and SO₄^·-/·OH, respectively. This study clarifies the structure-activity relationships of PSBC for PMS activation, and opens a new avenue for the treatment and utilization of PS as high value-added resources.

Vermiremediation of allopathic pharmaceutical industry sludge amended with cattle dung employing Eisenia fetida

The present study aims to vermiremediate allopathic pharmaceutical industry sludge (AS) amended with cattle dung (CD), in different feed mixtures (AS:CD) i.e (AS₀) 0:100 [Positive control], (AS₂₅) 25:75, (AS₅₀) 50:50, (AS₇₅) 75:25 and (AS₁₀₀) 100:0 [Negative Control] for 180 days using earthworm Eisenia fetida. The earthworms could thrive and grow well up to the AS₇₅ feed mixture. In the final vermicompost, there were significant decreases in electrical conductivity (29.18-18.70%), total organic carbon (47.48-22.39%), total organic matter (47.47-22.36%), and C: N ratio (78.15-54.59%). While, significant increases in pH (9.06-16.47%), total Kjeldahl nitrogen (69.57-139.58%), total available phosphorus (30.30-81.56%), total potassium (8.92-22.22%), and total sodium (50.56-62.12%). The heavy metals like Cr (50-18.60%), Cd (100-75%), Pb (57.14-40%), and Ni (100-50%) were decreased, whereas Zn (8.37-53.77%), Fe (199.03-254.27%), and Cu (12.90-100%) increased significantly. The toxicity of the final vermicompost was shown to be lower in the Genotoxicity analysis, with values ranging between (76-42.33%). The germination index (GI) of Mung bean (Vigna radiata) showed a value ranging between 155.02 and 175.90%. Scanning electron microscopy (SEM) analysis showed irregularities with high porosity of texture in the final vermicompost than in initial mixtures. Fourier Transform-Infrared Spectroscopy (FT-IR) spectra of final vermicompost had low peak intensities than the initial samples. The AS₅₀ feed mixture was the most favorable for the growth and fecundity of Eisenia fetida, emphasizing the role of cattle dung in the vermicomposting process. Thus, it can be inferred that a cost-effective and eco-friendly method (vermicomposting) with the proper amendment of cattle dung and employing Eisenia fetida could transform allopathic sludge into a nutrient-rich, detoxified, stable, and mature vermicompost for agricultural purposes and further could serve as a stepping stone in the allopathic pharmaceutical industry sludge management strategies in the future.

FexN produced in pharmaceutical sludge biochar by endogenous Fe and exogenous N doping to enhance peroxymonosulfate activation for levofloxacin degradation

For preparing high performance biochar to be applicated in persulfate-based oxidation treatment of wastewater, the feasibility of deriving Fe-N biochar from pharmaceutical sludge by endogenous Fe and exogenous N doping was investigated. With exogenous urea doping, Fe_xN contained biochar (PZBC800U) was successfully derived from endogenous Fe(OH)₃ contained pharmaceutical sludge. PZBC800U effectively activated peroxymonosulfate (PMS) to remove 80 mg·L^-1 levofloxacin (LEV) within 90 min. The main mechanism of PMS activation by PZBC800U for LEV degradation was revealed as non-radical pathways dominated by ¹O₂ generation and direct electron transfer. The formation of Fe_xN combined with the increase of pyridinic-N in the biochar changed the electronic structure, improved the electron transfer ability, and thus achieved the excellent PMS activation capacity of the biochar. The vital function of endogenous Fe(OH)₃ was verified by comparing PZBC800U to Fe leached and extra Fe added controls. A total of 18 intermediates in the degradation of LEV were identified, and degradation pathways were proposed. Combined with the average local ionization energy calculation, the priority of piperazine breakage during LEV degradation was experimentally proved and mechanistically elucidated. This study provides a new insight into Fe_xN biochar preparation from pharmaceutical sludge and the mechanisms of its excellent PMS activation performance for LEV degradation.

Pyrolyzing pharmaceutical sludge to biochar as an efficient adsorbent for deep removal of fluoroquinolone antibiotics from pharmaceutical wastewater: Performance and mechanism

This study explored the impact of pyrolysis parameters and modification methods on the characteristics of pharmaceutical sludge biochar, and investigated its capacity and mechanisms for levofloxacin (LEV), a typical fluoroquinolone antibiotics, adsorption. The results showed that S_BET of the biochar was improved with temperature increase, but decreased when temperature reached 900 °C. Under the optimal pyrolysis condition of 800 °C and 90 min, the biochar possessed the highest S_BET of 264.05 m² g^-1, excellent iodine value of 401.41 ± 3.84 mg∙g^-1 and phenol adsorption of 57.36 ± 3.39 mg∙g^-1. Among KOH, ZnCl₂, and CO₂ modifications, ZnCl₂ modification achieved the highest phenol adsorption of 123.40 ± 4.65 mg g^-1, with a significantly improved S_BET of 534.91 m² g^-1. The maximum LEV adsorption capacity of ZnCl₂ modified biochar, PZBC800, reached 159.26 mg g^-1, which overwhelmed the reported sludge biochars. BET, zeta potential, FT-IR, XPS, and Raman analysis, along with quantum chemistry calculation, revealed that pore filling, hydrogen bonding, π-π interaction, surface complexation, and electrostatic interaction were the main mechanisms for the excellent LEV adsorption performance of PZBC800. Deep removal (99.9%) of Fluoroquinolones (FQs) from pharmaceutical wastewater was also achieved by PZBC800 adsorption. The study promoted the development of pharmaceutical sludge biochar preparation and its application in advanced treatment of FQs pharmaceutical wastewater.

The characteristics of pharmaceutical sludge-derived biochar and its application for the adsorption of tetracycline

In this study, the specific surface area, pore structure, surface functional groups and microstructure of the biochar derived from the pyrolysis of pharmaceutical sludge are analyzed. The results showed that the pyrolysis temperature had a great influence on the properties of sludge-based biochar (SBB), and the specific surface area of the SBB first increased and then decreased with an increase in the pyrolysis temperature. The maximum specific surface area was 214.97 m²/g at 600 °C, while the pore volume increased with an increase in the pyrolysis temperature. The pickling process removed impurities in the SBB and increased the specific surface area of the material (319.80 m²/g). The effects of pyrolysis temperature, pH, adsorption time, and initial pollutant concentration on the adsorption process were also studied. The results showed that the adsorbents had good pH adaptability, and biochar produced at 600 °C had the best adsorption capacity (94.69 mg/g). Pickling increased the adsorption capacity to 157.38 mg/g. The results showed that pharmaceutical sludge has great potential as a raw material for the preparation of adsorbent. These benefits can compensate for the cost of sludge pyrolysis treatment.

Preparation of porous biochar based on pharmaceutical sludge activated by NaOH and its application in the adsorption of tetracycline

In this study, two different kinds of pharmaceutical sludge activated by NaOH were used to prepare biochar. The characteristics of biochar prepared by impregnation method and dry mixing method were analyzed, including N₂ adsorption-desorption isotherms, surface functional group analysis and micromorphological observation. The results showed that the biochar prepared by impregnation method had more micropores, while that prepared by dry mixing activation method had more mesopores. The adsorption reaction of tetracycline on the two different kind of biochar was investigated. Several important factors such as solution initial pH, tetracycline concentration and reaction time on adsorption reaction were investigated. The results show that both kinds of biochar have high tetracycline adsorption efficiency and excellent pH adaptability. The biochar manufactured by dry mixing activation method had better adsorption performance (379.78 mg/g, 25 °C). Regeneration experiments showed that the adsorbent had stable performance in absorbing tetracycline. Direct dry mixing activation method is a simple and effective method used to prepare porous biochar, which can be used for the resourceful utilization of pharmaceutical sludge. This work provides extensive information on the use of biochar derived from pharmaceutical sludge for the removal of TC from hospital and pharmaceutical production wastewater.

Comparison of ozone and thermal hydrolysis combined with anaerobic digestion for municipal and pharmaceutical waste sludge with tetracycline resistance genes

Biosolids from wastewater treatment plant (WWTP) are environmental reservoirs of antibiotic resistance genes, which attract great concerns on their efficient treatments. Anaerobic digestion (AD) is widely used for sewage sludge treatment but its effectiveness is limited due to the slow hydrolysis. Ozone and thermal hydrolysis pre-treatment were employed to improve AD efficiency and reduce antibiotic-resistant genes in municipal and pharmaceutical waste sludge (MWS and PWS, respectively) in this study. Sludge solubilization achieved 15.75-25.09% and 14.85-33.92% after ozone and thermal hydrolysis, respectively. Both pre-treatments improved cumulative methane production and the enhancements were greater on PWS than MWS. Five tetracycline-resistant genes (tet(A), tet(G), tet(Q), tet(W), tet(X)) and one mobile element (intI1) were qPCR to assess pre-treatments. AD of pre-treated sludge reduced more tet genes than raw sludge for both ozonation and thermal hydrolysis in PWS and MWS. Thermal hydrolysis pre-treatment was more efficient than ozone for reduction after AD. Results of this study help support management options for reducing the spread of antibiotic resistance from biosolids.

Preparation and characterization of green bricks using pharmaceutical industrial wastes

This paper reports on recycling of industrial wastes (three pharmaceutical industrial sludges) into environmental friendly value-added materials. Stabilization/Solidification (S/S or bricks) process was applied to make a safer way for the utilization of pharmaceutical waste. The additives in this study include binders (cement, lime and bentonite) and strengthening material (pulverized fuel ash (PFA), silica fume and quarry dust) was used at different compositions. Bricks were cured for 28 days, and the following analysis-like compressive strength, leachability of heavy metals, mineralogical phase identity by X-ray diffraction (XRD) spectroscopy, Fourier transform infrared spectroscopy (FTIR) and thermal behaviour by thermogravimetric-differential thermal analysis (TG-DTA) had done. All the bricks were observed to achieve the standard compressive strength as required for construction according to BIS standards. Metal concentration in the leachate has reached the dischargeable limits according to Brazilian standards. Results of this study demonstrate that production of bricks is a promising and achievable productive use of pharmaceutical sludge.

The fate of a nitrobenzene-degrading bacterium in pharmaceutical wastewater treatment sludge

This paper describes the fate of a nitrobenzene-degrading bacterium, Klebsiella oxytoca NBA-1, which was isolated from a pharmaceutical wastewater treatment facility. The 90-day survivability of strain NBA-1 after exposure to sludge under anaerobic and aerobic conditions was investigated. The bacterium was inoculated into sludge amended with glucose and p-chloronitrobenzene (p-CNB) to compare the bacterial community variations between the modified sludge and nitrobenzene amendment. The results showed that glucose had no obvious effect on nitrobenzene biodegradation in the co-metabolism process, regardless of the presence/absence of oxygen. When p-CNB was added under anaerobic conditions, the biodegradation rate of nitrobenzene remained unchanged although p-CNB inhibited the production of aniline. The diversity of the microbial community increased and NBA-1 continued to be one of the dominant strains. Under aerobic conditions, the degradation rate of both nitrobenzene and p-CNB was only 20% of that under anaerobic conditions. p-CNB had a toxic effect on the microorganisms in the sludge so that most of the DGGE (denaturing gradient gel electrophoresis) bands, including that of NBA-1, began to disappear under aerobic conditions after 90days of exposure. These data show that the bacterial community was stable under anaerobic conditions and the microorganisms, including NBA-1, were more resistant to the adverse environment.

Effect of ultrasonic and ozone pre-treatments on pharmaceutical waste activated sludge's solubilisation, reduction, anaerobic biodegradability and acute biological toxicity

Ultrasonic and ozone pre-treatment technologies were employed in this study to improve the anaerobic digestion efficiency of pharmaceutical waste activated sludge. The sludge solubilisation achieved 30.01% (150,000 kJ/kg TS) and 28.10% (0.1g O3/g TS) after ultrasonic treatment and ozone treatment. The anaerobic biodegradability after ultrasonic treatment was higher compared to ozonation due to the higher cumulative methane volume observed after 6 days (249 ml vs 190 ml). The ozonated sludge released the highest concentration of Cu(2+) into the liquid phase (6.640 mg L(-1)) compared to 0.530 mg/L for untreated sludge and 0.991 mg/L for sonicated sludge. The acute toxicity test measured by luminescent bacteria showed that anaerobic digestion could degrade toxic compounds and result in a reduction in toxicity. The main mechanism of action led to some differences in the treated sludge exhibiting higher potential for methane production from pharmaceutical waste sludge with ultrasonic treatment.

Study on anaerobic digestion treatment of hazardous colistin sulphate contained pharmaceutical sludge

Pharmaceutical sludge is considered as a hazardous substance with high treatment and disposal fees. Anaerobic digestion could not only transform the hazardous substance into activated sludge, but also generate valuable biogas. This research had two objectives. First: studying the feasibility of anaerobic digestion and determining the biochemical methane potential (BMP) of pharmaceutical sludge under different Inoculum to substrate TS ratios (ISRs) of 0, 0.65, 2.58 and 10.32 in mesophilic condition of 37±1°C. Secondly, investigating the removal efficiency of colistin sulphate during anaerobic digestion. The results showed that the use of anaerobic digestion to treat the pharmaceutical sludge is feasible and that it can completely eliminate the colistin sulphate. The highest biogas production from pharmaceutical sludge is 499.46 mL/g TS at an ISR of 10.32.