Screening and Optimization of Conditions for the Adsorption of Cd2+ in Serpentine by Using Response Surface Methodology

Our plain-English summary of Screening and Optimization of Conditions for the Adsorption of Cd2+ in Serpentine by Using Response Surface Methodology, by X. Zhang, L. Du, W. Jin (International Journal of Environmental Research and Public Health, 2022).

The study

• Authors: X. Zhang, L. Du, W. Jin
• Journal: International Journal of Environmental Research and Public Health
• Published: 2022;19(24)
• Cited by: 2 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

In order to explore the optimal conditions for the adsorption of Cd2+ in serpentine, this paper studied the adsorption of simulated cadmium solutions with serpentine as an adsorbent. On the basis of a single factor experiment, four factors including the amount of serpentine, initial pH, the initial concentration of solutions, and adsorption time were selected as the influencing factors, and the adsorption quantity and adsorption rate of serpentine to Cd2+ were double response values using the Box-Behnken design. Response surface analyses were used to study the effects of four factors on the adsorption quantity and adsorption rate of serpentine on cadmium, and the interaction between various factors. The results showed that the optimum adsorption conditions were as follows: the amount of serpentine was 1%, the initial pH was 5.5, the initial solution concentration was 40.83 mg·L-1, and the adsorption time was 26.78 h. Under these conditions, the theoretical adsorption quantity and adsorption rate of serpentine to Cd2+ were 3.99 mg·g-1 and 95.24%, respectively. At the same time, after three repeated experiments, the actual adsorption quantity and adsorption rate of serpentine to Cd2+ were 3.91 mg·g-1 and 94.68%, respectively, and the theoretical value was similar to the actual value. Therefore, it was proved that the experimental design of the regression model is reliable, and it is feasible to use the response surface method to optimize the adsorption conditions of serpentine on Cd2+.

In plain English

This laboratory study tested whether serpentine, a magnesium silicate mineral, can remove cadmium from simulated cadmium solutions. The serpentine came from Xiuyan County, Liaoning Province, China, and X-ray analysis identified it as antigorite. The authors heated it at 700 degrees C for 2 hours. This turned it into forsterite and increased its surface area and pore volume. The heated serpentine had a higher maximum cadmium uptake than natural serpentine. Using heated serpentine, the authors next varied one factor at a time: amount of serpentine, starting pH, starting cadmium concentration and contact time. They then used a 29-run Box–Behnken statistical design. Serpentine amount and cadmium concentration were the leading factors for uptake; the main effects of pH and time were not significant, though a squared time term was. The model's best conditions were 1% serpentine, pH 5.5, 40.83 mg per litre cadmium and 26.78 hours. These conditions predicted 3.99 mg of cadmium per gram and 95.24% removal, and three check runs averaged 3.91 mg per gram and 94.68%. The authors concluded that this optimization method is feasible. The study did not examine asbestos or human health.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: laboratory adsorption experiment: equilibrium (isotherm) tests, single-factor experiments, then a Box–Behnken response surface design
• Who was studied: not people: natural serpentine (S-0) from Xiuyan County, Anshan City, Liaoning Province, China, and the same serpentine heat-treated at 700 degrees C (S-700), tested in simulated cadmium solutions
• Exposure: no human exposure was studied. Variables tested for cadmium (Cd2+) adsorption were the amount of serpentine (1% to 5%), initial pH (2 to 6.5), initial cadmium concentration (10 to 200 mg per litre) and adsorption time (0.5 to 28 hours)
• Main results:
  • Natural serpentine was identified as antigorite. After heating at 700 degrees C the antigorite peaks disappeared and the material was transformed into forsterite
  • Heated serpentine (S-700) had greater specific surface area and pore volume than natural serpentine (S-0). Table 3 gives BET surface areas of 13.7 versus 6.1 m2 per g
  • In the equilibrium experiment comparing natural and heated serpentine, Langmuir fitting gave a higher maximum cadmium adsorption quantity for heated serpentine than for natural serpentine
  • In single-factor tests, raising the cadmium concentration to 200 mg per litre gave the largest adsorption quantity but a removal rate of only 47.63%
  • In the regression model for adsorption quantity, the factor ranking was amount of serpentine, then concentration, then time, then pH. The main effects of pH and time were not significant, but the squared time term (D2) was significant in Table 6 (p = 0.0232)
  • Predicted optimal conditions were 1% serpentine, pH 5.5, 40.83 mg per litre and 26.78 hours, giving a predicted adsorption quantity of 3.99 mg per g and a removal rate of 95.24%
  • Three verification runs averaged an adsorption quantity of 3.91 mg per g and a removal rate of 94.68%
• The authors' conclusion: The authors concluded that the verification results matched the software predictions, showing that using response surface methodology to optimize cadmium adsorption by serpentine is feasible
• Limitations the authors state:
  • The authors note that other ions present together with cadmium might affect adsorption, and that this had not yet been tested
  • The authors note that the zero potential of serpentine was not measured and should be considered

Topics

The National Library of Medicine indexes this study under subjects our site covers: Chrysotile.

Medical terms in this study, explained in our Lexicon: Serpentine Group.

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