Salahedin Moradi

Chlorella vulgaris is an inexpensive microalga that could be employed for environmental remediation, but further investigations are needed to assess its suitability and optimal treatment methodology. With this aim in mind, this study focused on the raw biomass and the biochar and hydrochar obtained from it, analyzing their physicochemical properties and testing them to capture cadmium from an aqueous environment. The adsorption/absorption tests assessed the effect of adsorbent dosage, pH, Cd concentration, and contact time, and the results were analyzed through a structural equation model. Biochar and hydrochar performed similarly and better than the raw biomass, with the highest Cd removal observed at an adsorbent dosage of 0.8 g L⁻¹, an initial concentration of Cd solution of 30 mg L⁻¹, a pH of 6, and a contact time of 30 min. The adsorption isotherm data for Cd could be well-described by the Langmuir and Temkin models. The results from the structural equation modeling revealed that the variables material type, dosage, and concentration all contributed to Cd removal in water, with time mediating these effects.

Chlorella Vulgaris is an inexpensive and accessible raw material that can be evaluated for environmental remediation. As its derivatives have the potential for environmental pollutant removal, further investigations to evaluate their feasibility for this purpose are needed. This study aimed to investigate and compare the physiochemical properties of Chlorella Vulgaris algae biomass with biochar and hydrochar derived from it. This study was conducted in a completely randomized block design with three replicates at the University of Zanjan, Iran. The detailed physico-chemical characterization of three substances (algae biomass with biochar and hydrochar) was measured. Adsorption isotherms were used to explain the adsorption process. The effects of the adsorbents dosage (0.1, 0.2, 0.4, 0.8, 1, and 2 g), pH (3, 5, 6, 7, 8, and 9), initial cadmium (Cd) concentration (0, 2, 5, 10, 20, and 40 mg l^− 1), and contact time (0, 5, 15, 30, 60, 90, and 180 minutes) on Cd removal were evaluated. The carbon content, ash content, volatile matter, and specific surface area of biochar and hydrochar are higher, while hydrogen, oxygen, nitrogen, and sulfur are lower compared to algae biomass. Results showed that FTIR spectra of algae biomass, biochar, and hydrochar followed a similar trend, but the corresponding biochar showed fewer peaks than microalgae, and the peaks were sharper and taller. For biochar, hydrochar, and algae biomass, the maximum adsorption capacities for Cd were 24.39, 23.58, and 16.56 mg g^− 1, respectively. Optimum conditions for the highest removal of Cd were observed at the adsorbents dosage of 0.8 g l^− 1, 30 mg l^− 1 initial concentration of Cd solution, pH of 6, and contact time of 30 minutes. The adsorption isotherm data of Cd could be well-described by the Langmuir and Temkin models. The results indicated that biochar, hydrochar, and algae biomass could be used as a biosorbent for the removal of heavy metals from aqueous streams.

Cadmium (Cd) is one of the toxic elements entering the food chain in various ways, including chemical fertilizers. This study aimed to assess different amounts and forms of available Cd in soils under wheat cultivation affected by long-term use of phosphorus chemical fertilizers and also to study the rate of Cd intake by people with age and gender differences. To investigate the Cd status in wheat-cultivated lands, 105 soil samples and also 24 wheat samples were collected from three land uses of rainfed, irrigated, and control one. Phosphorus levels were also measured in soil samples to investigate the relationship between the amount of chemical fertilizer consumption and the amount of Cd. The mean values of available Cd were 0.15, 0.18, and 0.08 (mg/kg) under three land-use types of rainfed, irrigated, and control one, respectively, and the mean values of total Cd were also 1.9, 2.22, and 1.30 in the rainfed land, irrigated land, and control one, respectively. The results showed that the amount of available and total Cd in the irrigated and rainfed lands was higher than the amount of Cd in the control sample. According to the results of Cd fractionation, the highest amounts of Cd were in the residual, carbonate, organic, soluble, and exchangeable fractions, respectively. The amounts of Cd in the three parts of root, stem, and grain were 1.08, 0.65, 0.91 (mg/kg), respectively. Finally, the results showed that the rate of Cd entry into the children’s body was higher than that of adults and the elderly.

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