Access to drinkable water is becoming more and more challenging due to worldwide pollution and the cost of water treatments. Water and wastewater treatment by adsorption on solid materials is usually cheap and effective in removing contaminants, yet classical adsorbents are not sustainable because they are derived from fossil fuels, and they can induce secondary pollution. Therefore, biological sorbents made of modern biomass are increasingly studied as promising alternatives. Indeed, such biosorbents utilize biological waste that would otherwise pollute water systems, and they promote the circular economy. Here we review biosorbents, magnetic sorbents, and other cost-effective sorbents with emphasis on preparation methods, adsorbents types, adsorption mechanisms, and regeneration of spent adsorbents. Biosorbents are prepared from a wide range of materials, including wood, bacteria, algae, herbaceous materials, agricultural waste, and animal waste. Commonly removed contaminants comprise dyes, heavy metals, radionuclides, pharmaceuticals, and personal care products. Preparation methods include coprecipitation, thermal decomposition, microwave irradiation, chemical reduction, micro-emulsion, and arc discharge. Adsorbents can be classified into activated carbon, biochar, lignocellulosic waste, clays, zeolites, peat, and humic soils. We detail adsorption isotherms and kinetics. Regeneration methods comprise thermal and chemical regeneration and supercritical fluid desorption. We also discuss exhausted adsorbent management and disposal. We found that agro-waste biosorbents can remove up to 68–100% of dyes, while wooden, herbaceous, bacterial, and marine-based biosorbents can remove up to 55–99% of heavy metals. Animal waste-based biosorbents can remove 1–99% of heavy metals. The average removal efficiency of modified biosorbents is around 90–95%, but some treatments, such as cross-linked beads, may negatively affect their efficiency.

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Wastewater from slaughter houses (abattoirs) has been a problem in Nigeria. It is complex and difficult to treat. The potentials of novel Fish Bone Chito-protein (FBC) successfully extracted through de-proteinization of Fish Bone Flour (FBF) were explored for the reduction of particle load in abattoir wastewater. Extracted FBC sample was analysed via proximate analysis and instrumental characterizations viz: X-ray Fluorescence (XRF) analysis, Scanning Electron Microscopy (SEM) and Fourier Transform Infrared Spectrophotoscopic Analysis (FTIR). Influences of coagulant dosage, pH, settling time and temperature were studied. The rate of particle uptake was studied using seven kinetic models. Proximate characterization of FBC revealed that it contains 24% protein, 43% carbohydrate and other components in trace values. Before treatment, abattoir wastewater contains (563 mg/L) suspended particles in excess of the national discharge standard. 92% of the particle load was removed after the coagulation treatment with 1.5g of FBC, after 35 min at pH 2, and 40 °C. BOD removal of 58% was also obtained at the same conditions. The best kinetics model selection was done between Pseudo Second Order (PSO) and fractional power (FP) kinetic model via one way statistical mean comparison using ANOVA and turkey pairwise p-values. The ANOVA p-value for pseudo second order (0.001) was found to be ˂ 0.005 (model significance alpha value). Also, the difference between the adjusted and predicted R 2 value (0.0018) was less than 0.2. Thus, pseudo second order described the kinetic data with precision. The mechanistic pathway analysis for the process particle uptake was governed by intra-particle diffusion and film/surface diffusion. The results summarized indicate that fish bones are no waste, FBF is good source of coagulant.