This work highlights the potential of corncob biochar (CCBC) and Brevibacillus parabrevis for the decolorization of brilliant green (BG) dye from synthetically prepared contaminated wastewater. The CCBC was characterized by proximate, Fourier-transform infrared spectroscopy, scanning electron microscopy, X-ray diffraction, and Brunauer–Emmett–Teller analysis, respectively. Different parameters affecting the adsorption process were evaluated. The experimental results were analyzed by the Langmuir and Freundlich isotherm models. Kinetic results were examined by different models; pseudo-second-order model has shown the best fit to the experimental data. Anew positive values of ΔH^o (172.58 kJ/mol) and ΔS^o (569.97 J/K/mol) in the temperature range of 303–318 K revealed that the adsorption process was spontaneous and endothermic. The present investigation showed that the bacteria immobilized with CCBC showed better BG dye degradation. The kinetic parameters, μ_max, Ks, and μ_max, were found to be 0.5 per day, 39.4 mg/day, and 0.012 L/mg/day using Monod model, respectively. The adsorbent with bacteria showed good potential for the removal of cationic BG dye and can be considered for the remediation of industrial effluent. Graphical abstract

This paper will focus on the challenges associated with algae-based wastewater treatment (ABWWT). To elucidate the issue, this review will investigate the following: (1) microalgal strain selection, (2) wastewater characteristics, and (3) the effect of various biotic and abiotic factors. Mostly, monocultures of microalgae are used in wastewater treatment (WWT), but microalgae–bacteria consortia have received significant attention recently. Their interaction mechanisms and the sheer number of possible combinations pose a significant challenge in the strain selection. Various types of wastewaters have varying nutrient loads and different types of biochemical composition, which affect the efficiency of their treatment process significantly. Because microalgae are photosynthetic organisms, environmental factors, such as light, temperature, and pH play a significant role in the phycoremediation of wastewater. Light intensity and its duration, the maintenance of optimum temperature, and pH range pose major challenges in ABWWT. In addition to abiotic factors, biotic factors, such as biopollutants that include pathogenic microorganisms greatly affect the quality of treated wastewater. Their proper detection and elimination is a significant requirement in the wastewater process. Therefore, this paper will carry out a critical review of all the previously mentioned key challenges, which act as an impediment in the large scale implementation of ABWWT.

Microporous activated carbon was prepared from almond shell powder and activated with H₃PO₄ and was used for the removal of Cr (VI). The characterization of activated carbon was done for Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET) surface area measurement and elemental analysis. The batch experiments were conducted to study the effects of contact time, solution pH, adsorbent dose, initial chromium concentration and temperature on removal of Cr (VI). The Cr (VI) removal was found to be 100% at an initial pH of 2. The equilibrium data for the adsorption of Cr (VI) on the adsorbent were fitted with Langmuir, Freundlich, Temkin and Dubinin–Radushkevich adsorption isotherm models. The Langmuir isotherm model fitted better and values of model parameters q_m, b, R² and R_L were found to be 195, 0.024, 0.98 and 0.45, respectively. Adsorption kinetics was analyzed for the pseudo first order, pseudo second order and intra-particle diffusion situations. Thermodynamic parameters revealed the spontaneous, endothermic and increased randomness nature of the adsorption process. The values of Δ H° and Δ S° were found to be 22.9 KJ/mol and 95.3 J/mol-K.