Preparation of Adsorbents by Pyrolysis of Sludge Mixed With Steel Slag and Study on Adsorption of Chromium Ions in Water

In this study, the dewatered sludge from the sewage plant and the open-hearth steel slag of the steel plant are used as raw materials. As two wastes, they were mixed and pyrolyzed to prepare a composite absorbent. Further, the adsorption mechanism of the adsorbent to chromium ions in the sewage is explored. The pyrolysis reaction behavior of sludge mixed with steel slag was studied by the thermogravimetric analysis technology. SEM, BET, and XPS were used to analyze the specific surface area, pore size distribution, and pore structure characteristics of pyrolysis products, respectively. Moreover, a comprehensive analysis of the adsorbent was carried out for the adsorption mechanism of hexavalent chromium ions. The results show that the addition of steel slag promotes the pyrolysis of the sludge in each stage. When the content of steel slag is 80%, the increases of reaction rate are the most obvious with the largest increase of weight loss rate in each stage. The SEM results show that the enrichment of sludge on metal oxides is enhanced in the high-temperature range (600–700°C). Besides, when the content of steel slag is 40–60%, the mixture’s growth rate of the specific surface area can reach 600% and the growth rate of total pore volume can reach 350% (the situations of sludge as the baseline). Regarding the measurement of Cr(VI), the adsorption rate of the steel-slag solution is 50.93% and that of the sludge solution is 69%. However, the adsorption rate can be increased to 95% when the steel slag and sludge were mixed as an adsorption solution. In conclusion, the adsorption mechanism of Cr(VI) by additives is controlled by both physical and chemical processes. The present study provides a theoretical basis and technical support for the scientific and reasonable utilization of sludge and steel slag.

Uncertainty analysis for the data-driven model using Monte Carlo simulations to predict sodium adsorption rate: A case study, Aras, Sepid-Rud, and Karun Rivers in Iran

Water quality management requires a profound understating of future variations of surface and groundwater qualities for assessment and planning for human consumption, industrial, and irrigation purposes. In this regard, mathematical models, such as Box-Jenkins time series models, Bayesian time series models, and data-driven models are available for future prediction of water quality. However, the uncertainty associated with forecasting is one of the main problems of using these models towards water quality and future planning. In the present work, the uncertainty of the Adaptive Neuro-Fuzzy Inference System, based on Fuzzy c-means clustering, (ANFIS-FCMC) (genfis 3) model is quantified to analyze and predict Sodium Adsorption Rate(SAR) of water of Aras, Sepid-Rud, and Karun Rivers by using Monte Carlo simulations. The results indicate the combined standard and the expanded uncertainty simulated for SAR of Aras River water are 0.58 and1.16, respectively, and the gap is 2 .412 ±1.1622. Also, the combined standard and the expanded uncertainty simulated for SAR of Spid-Rud River water were1.11 and 2.22, respectively, and the gap is equal to 2 .235 ±2.22. Furthermore, the combined standard and the expanded uncertainty simulated for SAR of Aras River water are 2.063, and 4.126, respectively, and the gap is 4.79 ±4.126. Finally, the minimum uncertainty happened to predict SAR of Aras River using ANFIS-FCMC (genfis3) model and maximum SAR uncertainty belong to Karun River.

CO2 Adsorption and Desorption by Waste Ion-Exchange Resin–Based Activated Carbon on Fixed Bed

The waste ion-exchange resin–based activated carbon (WIRAC) was utilized for CO2 adsorption. The effect of adsorption temperature, gas flow, CO2 concentration, and adsorbent filling content on CO2 adsorption properties of WIRAC and the effect of desorption temperature and sweep gas flow on CO2 desorption performances of WIRAC were researched. In the adsorption process, with the increase of adsorption temperature, the CO2 adsorption capacity and adsorption rate decrease; as the gas flow increases, the CO2 adsorption capacity decreases, but the adsorption rate increases; with the increase of CO2 concentration and adsorbent filling content, the CO2 adsorption capacity and adsorption rate both increase. In the desorption process, the higher the desorption temperature and the smaller the sweep gas flow, the higher the CO2 purity of product gas and the longer the desorption time. In order to make sure the adsorbent be used efficiently and the higher CO2 concentration of product gas, the adsorption and desorption conditions selected should be a suitable choice.

Effect of the coexistence of SO32− and PO43− on the adsorption performance of zeolite-loaded FeOOH@ZnO for S2−

The present study deals with the synthesis of zeolite-loaded FeOOH@ZnO by hydrothermal method and investigates the effects of coexisting SO32− and PO43− ions in the aqueous solution on the adsorption performance for S2−. The results showed that the HNO3-modified zeolite loaded with FeOOH@ZnO (FeOOH@ZnO/HZ) resulted in a maximum S2− removal rate of ≈98%. The adsorbent's performance on removing S2− was significantly enhanced, compared with NaOH and ZnCl2-modified zeolites loaded with FeOOH@ZnO, and the adsorption was proved to be a heat-absorbing process. When SO32− and PO43− coexisted with S2−, SO32− and PO43− had a significant influence on the adsorption properties of FeOOH@ZnO/HZ. When three ions of S2−, SO32− and PO43− were present simultaneously, the adsorption performance of FeOOH@ZnO/HZ on S2− was further, and the removal rate dropped to about 80%. Moreover, FeOOH@ZnO/HZ also adsorbed PO43− and SO32− in the system containing multiple ions, but the adsorption rate of PO43− and SO32− were much lower than S2−. This indicated that the adsorption of S2− in the presence of FeOOH@ZnO/HZ dominates under competitive conditions.

Effect of Reaction Temperature on Adsorption Efficiency using Computer Mathematical Statistics Visible Spectorphotometer

In this paper, waste shrimp shells extracted from the head of the chitosan material; static adsorption experiments manner by wastewater containing Fe(III) added chitosan, vis spectrophotometer absorbance before and after the measurement experiment was obtained by reacting the size of the metal ion concentration, adsorption conditions whereby chitosan Fe(III) and the ability to explore. Experiments show that. In the case where the reaction temperature is less than 55°C, chitosan has adsorption rate Fe(III) smaller rise, the optimum temperature was 55°C, but the effects on the reaction temperature adsorption rate is not large; Adsorption when control time 30 min to 50 min, the absorption effect is increased with increase in the time, to reach the optimal reaction time 50 min.

Adsorption Features of Loess Calcareous Nodules to Heavy-Metal Ions in Aqueous Solution

This paper explores the use of calcareous tuberculosis as an adsorbent and heavy-metal ions (Cu2+, Zn2+, Cd2+, and Pb2+) as adsorbates, and the influence of varying levels of particle size, adsorption time, pH, adsorbent dosage, and initial concentration of heavy metals is studied through an experiment of single heavy-metal adsorption. In addition, the impact of the temperature and other factors on the adsorption of heavy-metal ions by calcareous nodules is analyzed to identify the optimal conditions for the adsorption of heavy-metal ions by calcareous nodules. As shown by the research findings, the adsorption rates of Cu2+, Zn2+, and Pb2+ gradually declined with the increase in particle size, with no evident effect on Cd2+. In the meantime, with further increases in factors such as the adsorption time, adsorbent dosage, and temperature, the adsorption rates of Cu2+, Zn2+, Cd2+, and Pb2+ experienced gradual increases. The adsorption rates of Cu2+, Zn2+, and Cd2+ gradually declined with the increase in initial concentration of heavy-metal ions, whereas the adsorption rate of Pb2+ experience increased first and then declined. As the pH increased, the adsorption rate of Cd2+ experience increased first and then declined at a slow pace. The adsorption rates of Cu2+, Zn2+, and Pb2+ increased first and then decreased. The adsorption capacity of calcareous nodules toward the four heavy-metal ions was in the order of Pb2+ > Zn2+ > Cu2+ > Cd2+. When the particle size was set to 0.25 mm, the adsorption time was set to 120 min, and the dosage was set to 0.6 g, the calcareous nodules included Pb2+, Zn2+, and Cu2+. Moreover, Cd2+ was able to achieve stronger adsorption capacity, with the adsorption rate able to reach 83.33%, 77.78%, 73.81%, and 81.93% of its maximum level. Therefore, as the particle size of the heavy-metal ions decreased, the adsorption capacity generally became stronger. As the adsorption time increased, the temperature and the amount of adsorbent also increased. The optimal pH value for the adsorption of calcareous nodules toward Pb2+, Zn2+, Cu2+, and Cd2+ was found to be 7, 6, 5, and 8, respectively, and the optimal temperature was 50 °C. In summary, calcareous nodules are a natural, low-cost, and effective adsorbent.

Locust bean gum adsorption onto softwood kraft pulp fibres: isotherms, kinetics and paper strength

The adsorption of locust bean gum (LBG) onto Northern Bleached Softwood Kraft (NBSK) pulp improved paper tensile and burst strength and lowered refining energy by strengthening inter-fibre bonding. Adsorption kinetics and isotherms were investigated to develop a fundamental understanding of the adsorption mechanism. The adsorption rate followed pseudo-second-order kinetics and the activation energy was 99.34 kJ·mol−1, suggesting chemisorption. The adsorption rate constant increased rapidly with temperature from 25 to 45 °C (k = 1.93 to 24.03 g·mg−1·min−1), but the amount adsorbed at equilibrium decreased (qe = 1.91 to 0.48 mg·g−1 o.d. fibre). LBG adsorption to NBSK at 25 °C was consistent with the Langmuir adsorption model for LBG < 2.1 wt% of o.d. fibre, suggesting reversible, homogenous adsorption to a finite number of sites on the fibre surface. Refining to 3000 rev increased the heterogeneity of the NBSK pulp surface leading to multi-layer Freundlich adsorption with adsorption constant n = 5.00, and the equilibrium constant Kf = 2.57 mg·g−1·(mg·L−1)−1/n at 25 °C. Favorable adsorption conditions for negatively charged LBG were identified: 25 °C for 10 min, low dosage level (< 2 wt%), lightly refined (< 3000 rev) NBSK pulp at low fibre consistency (< 0.5 wt%), high agitation rate (> 150 r.p.m.), acidic or neutral conditions (pH 2–7) without salt addition. Graphic abstract